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postgresql/src/include/postmaster/postmaster.h

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Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
/*-------------------------------------------------------------------------
*
* postmaster.h
* Exports from postmaster/postmaster.c.
*
Update copyright for 2024 Reported-by: Michael Paquier Discussion: https://postgr.es/m/ZZKTDPxBBMt3C0J9@paquier.xyz Backpatch-through: 12
2024-01-04 02:49:05 +01:00
* Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
* Portions Copyright (c) 1994, Regents of the University of California
*
Remove cvs keywords from all files.
2010-09-20 22:08:53 +02:00
* src/include/postmaster/postmaster.h
Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
*
*-------------------------------------------------------------------------
*/
#ifndef _POSTMASTER_H
#define _POSTMASTER_H
Refactor postmaster child process launching Introduce new postmaster_child_launch() function that deals with the differences in EXEC_BACKEND mode. Refactor the mechanism of passing information from the parent to child process. Instead of using different command-line arguments when launching the child process in EXEC_BACKEND mode, pass a variable-length blob of startup data along with all the global variables. The contents of that blob depend on the kind of child process being launched. In !EXEC_BACKEND mode, we use the same blob, but it's simply inherited from the parent to child process. Reviewed-by: Tristan Partin, Andres Freund Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
2024-03-18 10:35:08 +01:00
#include "miscadmin.h"
Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
/* GUC options */
Apply PGDLLIMPORT markings broadly. Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 14:16:38 +02:00
extern PGDLLIMPORT bool EnableSSL;
Rename ReservedBackends variable to SuperuserReservedConnections. This is in preparation for adding a new reserved_connections GUC, but aligning the GUC name with the variable name is also a good idea on general principle. Patch by Nathan Bossart. Reviewed by Tushar Ahuja and by me. Discussion: http://postgr.es/m/20230119194601.GA4105788@nathanxps13
2023-01-20 21:32:08 +01:00
extern PGDLLIMPORT int SuperuserReservedConnections;
Add new GUC reserved_connections. This provides a way to reserve connection slots for non-superusers. The slots reserved via the new GUC are available only to users who have the new predefined role pg_use_reserved_connections. superuser_reserved_connections remains as a final reserve in case reserved_connections has been exhausted. Patch by Nathan Bossart. Reviewed by Tushar Ahuja and by me. Discussion: http://postgr.es/m/20230119194601.GA4105788@nathanxps13
2023-01-20 21:36:36 +01:00
extern PGDLLIMPORT int ReservedConnections;
Mark assorted variables PGDLLIMPORT. This makes life easier for extension authors who wish to support Windows. Brian Cloutier, slightly amended by me. Discussion: http://postgr.es/m/CAJCy68fscdNhmzFPS4kyO00CADkvXvEa-28H-OtENk-pa2OTWw@mail.gmail.com
2017-12-05 15:23:57 +01:00
extern PGDLLIMPORT int PostPortNumber;
Apply PGDLLIMPORT markings broadly. Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 14:16:38 +02:00
extern PGDLLIMPORT int Unix_socket_permissions;
extern PGDLLIMPORT char *Unix_socket_group;
extern PGDLLIMPORT char *Unix_socket_directories;
extern PGDLLIMPORT char *ListenAddresses;
extern PGDLLIMPORT bool ClientAuthInProgress;
extern PGDLLIMPORT int PreAuthDelay;
extern PGDLLIMPORT int AuthenticationTimeout;
extern PGDLLIMPORT bool Log_connections;
extern PGDLLIMPORT bool log_hostname;
extern PGDLLIMPORT bool enable_bonjour;
extern PGDLLIMPORT char *bonjour_name;
extern PGDLLIMPORT bool restart_after_crash;
extern PGDLLIMPORT bool remove_temp_files_after_crash;
Provide options for postmaster to kill child processes with SIGABRT. The postmaster normally sends SIGQUIT to force-terminate its child processes after a child crash or immediate-stop request. If that doesn't result in child exit within a few seconds, we follow it up with SIGKILL. This patch provides GUC flags that allow either of these signals to be replaced with SIGABRT. On typically-configured Unix systems, that will result in a core dump being produced for each such child. This can be useful for debugging problems, although it's not something you'd want to have on in production due to the risk of disk space bloat from lots of core files. The old postmaster -T switch, which sent SIGSTOP in place of SIGQUIT, is changed to be the same as send_abort_for_crash. As far as I can tell from the code comments, the intent of that switch was just to block things for long enough to force core dumps manually, which seems like an unnecessary extra step. (Maybe at the time, there was no way to get most kernels to produce core files with per-PID names, requiring manual core file renaming after each one. But now it's surely the hard way.) I also took the opportunity to remove the old postmaster -n (skip shmem reinit) switch, which hasn't actually done anything in decades, though the documentation still claimed it did. Discussion: https://postgr.es/m/2251016.1668797294@sss.pgh.pa.us
2022-11-21 17:59:29 +01:00
extern PGDLLIMPORT bool send_abort_for_crash;
extern PGDLLIMPORT bool send_abort_for_kill;
Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
Implement new PostmasterIsAlive() check for WIN32, per Claudio Natoli. In passing, align a few error messages with the style guide.
2004-05-30 05:50:15 +02:00
#ifdef WIN32
Apply PGDLLIMPORT markings broadly. Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 14:16:38 +02:00
extern PGDLLIMPORT HANDLE PostmasterHandle;
Introduce a pipe between postmaster and each backend, which can be used to detect postmaster death. Postmaster keeps the write-end of the pipe open, so when it dies, children get EOF in the read-end. That can conveniently be waited for in select(), which allows eliminating some of the polling loops that check for postmaster death. This patch doesn't yet change all the loops to use the new mechanism, expect a follow-on patch to do that. This changes the interface to WaitLatch, so that it takes as argument a bitmask of events that it waits for. Possible events are latch set, timeout, postmaster death, and socket becoming readable or writeable. The pipe method behaves slightly differently from the kill() method previously used in PostmasterIsAlive() in the case that postmaster has died, but its parent has not yet read its exit code with waitpid(). The pipe returns EOF as soon as the process dies, but kill() continues to return true until waitpid() has been called (IOW while the process is a zombie). Because of that, change PostmasterIsAlive() to use the pipe too, otherwise WaitLatch() would return immediately with WL_POSTMASTER_DEATH, while PostmasterIsAlive() would claim it's still alive. That could easily lead to busy-waiting while postmaster is in zombie state. Peter Geoghegan with further changes by me, reviewed by Fujii Masao and Florian Pflug.
2011-07-08 17:27:49 +02:00
#else
Apply PGDLLIMPORT markings broadly. Up until now, we've had a policy of only marking certain variables in the PostgreSQL header files with PGDLLIMPORT, but now we've decided to mark them all. This means that extensions running on Windows should no longer operate at a disadvantage as compared to extensions running on Linux: if the variable is present in a header file, it should be accessible. Discussion: http://postgr.es/m/CA+TgmoYanc1_FSfimhgiWSqVyP5KKmh5NP2BWNwDhO8Pg2vGYQ@mail.gmail.com
2022-04-08 14:16:38 +02:00
extern PGDLLIMPORT int postmaster_alive_fds[2];
Run pgindent on 9.2 source tree in preparation for first 9.3 commit-fest.
2012-06-10 21:20:04 +02:00
Introduce a pipe between postmaster and each backend, which can be used to detect postmaster death. Postmaster keeps the write-end of the pipe open, so when it dies, children get EOF in the read-end. That can conveniently be waited for in select(), which allows eliminating some of the polling loops that check for postmaster death. This patch doesn't yet change all the loops to use the new mechanism, expect a follow-on patch to do that. This changes the interface to WaitLatch, so that it takes as argument a bitmask of events that it waits for. Possible events are latch set, timeout, postmaster death, and socket becoming readable or writeable. The pipe method behaves slightly differently from the kill() method previously used in PostmasterIsAlive() in the case that postmaster has died, but its parent has not yet read its exit code with waitpid(). The pipe returns EOF as soon as the process dies, but kill() continues to return true until waitpid() has been called (IOW while the process is a zombie). Because of that, change PostmasterIsAlive() to use the pipe too, otherwise WaitLatch() would return immediately with WL_POSTMASTER_DEATH, while PostmasterIsAlive() would claim it's still alive. That could easily lead to busy-waiting while postmaster is in zombie state. Peter Geoghegan with further changes by me, reviewed by Fujii Masao and Florian Pflug.
2011-07-08 17:27:49 +02:00
/*
* Constants that represent which of postmaster_alive_fds is held by
* postmaster, and which is used in children to check for postmaster death.
*/
#define POSTMASTER_FD_WATCH 0 /* used in children to check for
* postmaster death */
#define POSTMASTER_FD_OWN 1 /* kept open by postmaster only */
Implement new PostmasterIsAlive() check for WIN32, per Claudio Natoli. In passing, align a few error messages with the style guide.
2004-05-30 05:50:15 +02:00
#endif
Mark assorted variables PGDLLIMPORT. This makes life easier for extension authors who wish to support Windows. Brian Cloutier, slightly amended by me. Discussion: http://postgr.es/m/CAJCy68fscdNhmzFPS4kyO00CADkvXvEa-28H-OtENk-pa2OTWw@mail.gmail.com
2017-12-05 15:23:57 +01:00
extern PGDLLIMPORT const char *progname;
Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
Add macros wrapping all usage of gcc's __attribute__. Until now __attribute__() was defined to be empty for all compilers but gcc. That's problematic because it prevents using it in other compilers; which is necessary e.g. for atomics portability. It's also just generally dubious to do so in a header as widely included as c.h. Instead add pg_attribute_format_arg, pg_attribute_printf, pg_attribute_noreturn macros which are implemented in the compilers that understand them. Also add pg_attribute_noreturn and pg_attribute_packed, but don't provide fallbacks, since they can affect functionality. This means that external code that, possibly unwittingly, relied on __attribute__ defined to be empty on !gcc compilers may now run into warnings or errors on those compilers. But there shouldn't be many occurances of that and it's hard to work around... Discussion: 54B58BA3.8040302@ohmu.fi Author: Oskari Saarenmaa, with some minor changes by me.
2015-03-11 14:19:54 +01:00
extern void PostmasterMain(int argc, char *argv[]) pg_attribute_noreturn();
Create a built-in log rotation program, so that we no longer have to recommend that people go get Apache's rotatelogs program. Additional benefits are that configuration is done through GUC, rather than externally, and that the postmaster can monitor the log rotator and restart it after failure (though we certainly hope that won't happen often). Andreas Pflug, some rework by Tom Lane.
2004-08-06 01:32:13 +02:00
extern void ClosePostmasterPorts(bool am_syslogger);
Refactor pid, random seed and start time initialization. Background workers, including parallel workers, were generating the same sequence of numbers in random(). This showed up as DSM handle collisions when Parallel Hash created multiple segments, but any code that calls random() in background workers could be affected if it cares about different backends generating different numbers. Repair by making sure that all new processes initialize the seed at the same time as they set MyProcPid and MyStartTime in a new function InitProcessGlobals(), called by the postmaster, its children and also standalone processes. Also add a new high resolution MyStartTimestamp as a potentially useful by-product, and remove SessionStartTime from struct Port as it is now redundant. No back-patch for now, as the known consequences so far are just a bunch of harmless shm_open(O_EXCL) collisions. Author: Thomas Munro Reviewed-by: Tom Lane Discussion: https://postgr.es/m/CAEepm%3D2eJj_6%3DB%2B2tEpGu2nf1BjthCf9nXXUouYvJJ4C5WSwhg%40mail.gmail.com
2018-10-19 02:59:14 +02:00
extern void InitProcessGlobals(void);
Pgindent run for 8.0.
2004-08-29 07:07:03 +02:00
Install a "dead man switch" to allow the postmaster to detect cases where a backend has done exit(0) or exit(1) without having disengaged itself from shared memory. We are at risk for this whenever third-party code is loaded into a backend, since such code might not know it's supposed to go through proc_exit() instead. Also, it is reported that under Windows there are ways to externally kill a process that cause the status code returned to the postmaster to be indistinguishable from a voluntary exit (thank you, Microsoft). If this does happen then the system is probably hosed --- for instance, the dead session might still be holding locks. So the best recovery method is to treat this like a backend crash. The dead man switch is armed for a particular child process when it acquires a regular PGPROC, and disarmed when the PGPROC is released; these should be the first and last touches of shared memory resources in a backend, or close enough anyway. This choice means there is no coverage for auxiliary processes, but I doubt we need that, since they shouldn't be executing any user-provided code anyway. This patch also improves the management of the EXEC_BACKEND ShmemBackendArray array a bit, by reducing search costs. Although this problem is of long standing, the lack of field complaints seems to mean it's not critical enough to risk back-patching; at least not till we get some more testing of this mechanism.
2009-05-05 21:59:00 +02:00
extern int MaxLivePostmasterChildren(void);
Allow discovery of whether a dynamic background worker is running. Using the infrastructure provided by this patch, it's possible either to wait for the startup of a dynamically-registered background worker, or to poll the status of such a worker without waiting. In either case, the current PID of the worker process can also be obtained. As usual, worker_spi is updated to demonstrate the new functionality. Patch by me. Review by Andres Freund.
2013-08-28 20:08:13 +02:00
extern bool PostmasterMarkPIDForWorkerNotify(int);
Background worker processes Background workers are postmaster subprocesses that run arbitrary user-specified code. They can request shared memory access as well as backend database connections; or they can just use plain libpq frontend database connections. Modules listed in shared_preload_libraries can register background workers in their _PG_init() function; this is early enough that it's not necessary to provide an extra GUC option, because the necessary extra resources can be allocated early on. Modules can install more than one bgworker, if necessary. Care is taken that these extra processes do not interfere with other postmaster tasks: only one such process is started on each ServerLoop iteration. This means a large number of them could be waiting to be started up and postmaster is still able to quickly service external connection requests. Also, shutdown sequence should not be impacted by a worker process that's reasonably well behaved (i.e. promptly responds to termination signals.) The current implementation lets worker processes specify their start time, i.e. at what point in the server startup process they are to be started: right after postmaster start (in which case they mustn't ask for shared memory access), when consistent state has been reached (useful during recovery in a HOT standby server), or when recovery has terminated (i.e. when normal backends are allowed). In case of a bgworker crash, actions to take depend on registration data: if shared memory was requested, then all other connections are taken down (as well as other bgworkers), just like it were a regular backend crashing. The bgworker itself is restarted, too, within a configurable timeframe (which can be configured to be never). More features to add to this framework can be imagined without much effort, and have been discussed, but this seems good enough as a useful unit already. An elementary sample module is supplied. Author: Álvaro Herrera This patch is loosely based on prior patches submitted by KaiGai Kohei, and unsubmitted code by Simon Riggs. Reviewed by: KaiGai Kohei, Markus Wanner, Andres Freund, Heikki Linnakangas, Simon Riggs, Amit Kapila
2012-12-06 18:57:52 +01:00
Refactor postmaster child process launching Introduce new postmaster_child_launch() function that deals with the differences in EXEC_BACKEND mode. Refactor the mechanism of passing information from the parent to child process. Instead of using different command-line arguments when launching the child process in EXEC_BACKEND mode, pass a variable-length blob of startup data along with all the global variables. The contents of that blob depend on the kind of child process being launched. In !EXEC_BACKEND mode, we use the same blob, but it's simply inherited from the parent to child process. Reviewed-by: Tristan Partin, Andres Freund Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
2024-03-18 10:35:08 +01:00
extern void BackendMain(char *startup_data, size_t startup_data_len) pg_attribute_noreturn();
Refactor EXEC_BACKEND code so that postmaster child processes reattach to shared memory as soon as possible, ie, right after read_backend_variables. The effective difference from the original code is that this happens before instead of after read_nondefault_variables(), which loads GUC information and is apparently capable of expanding the backend's memory allocation more than you'd think it should. This should fix the failure-to-attach-to-shared-memory reports we've been seeing on Windows. Also clean up a few bits of unnecessarily grotty EXEC_BACKEND code.
2004-12-29 22:36:09 +01:00
Refactor postmaster child process launching Introduce new postmaster_child_launch() function that deals with the differences in EXEC_BACKEND mode. Refactor the mechanism of passing information from the parent to child process. Instead of using different command-line arguments when launching the child process in EXEC_BACKEND mode, pass a variable-length blob of startup data along with all the global variables. The contents of that blob depend on the kind of child process being launched. In !EXEC_BACKEND mode, we use the same blob, but it's simply inherited from the parent to child process. Reviewed-by: Tristan Partin, Andres Freund Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
2024-03-18 10:35:08 +01:00
#ifdef EXEC_BACKEND
Convert the arithmetic for shared memory size calculation from 'int' to 'Size' (that is, size_t), and install overflow detection checks in it. This allows us to remove the former arbitrary restrictions on NBuffers etc. It won't make any difference in a 32-bit machine, but in a 64-bit machine you could theoretically have terabytes of shared buffers. (How efficiently we could manage 'em remains to be seen.) Similarly, num_temp_buffers, work_mem, and maintenance_work_mem can be set above 2Gb on a 64-bit machine. Original patch from Koichi Suzuki, additional work by moi.
2005-08-21 01:26:37 +02:00
extern Size ShmemBackendArraySize(void);
Refactor EXEC_BACKEND code so that postmaster child processes reattach to shared memory as soon as possible, ie, right after read_backend_variables. The effective difference from the original code is that this happens before instead of after read_nondefault_variables(), which loads GUC information and is apparently capable of expanding the backend's memory allocation more than you'd think it should. This should fix the failure-to-attach-to-shared-memory reports we've been seeing on Windows. Also clean up a few bits of unnecessarily grotty EXEC_BACKEND code.
2004-12-29 22:36:09 +01:00
extern void ShmemBackendArrayAllocation(void);
Move some functions from postmaster.c to a new source file This just moves the functions, with no other changes, to make the next commits smaller and easier to review. The moved functions are related to launching postmaster child processes in EXEC_BACKEND mode. Reviewed-by: Tristan Partin, Andres Freund Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
2024-03-18 10:35:05 +01:00
#ifdef WIN32
extern void pgwin32_register_deadchild_callback(HANDLE procHandle, DWORD procId);
#endif
Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
#endif
Refactor postmaster child process launching Introduce new postmaster_child_launch() function that deals with the differences in EXEC_BACKEND mode. Refactor the mechanism of passing information from the parent to child process. Instead of using different command-line arguments when launching the child process in EXEC_BACKEND mode, pass a variable-length blob of startup data along with all the global variables. The contents of that blob depend on the kind of child process being launched. In !EXEC_BACKEND mode, we use the same blob, but it's simply inherited from the parent to child process. Reviewed-by: Tristan Partin, Andres Freund Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi
2024-03-18 10:35:08 +01:00
/* defined in globals.c */
extern struct ClientSocket *MyClientSocket;
/* prototypes for functions in launch_backend.c */
extern pid_t postmaster_child_launch(BackendType child_type, char *startup_data, size_t startup_data_len, struct ClientSocket *sock);
const char *PostmasterChildName(BackendType child_type);
#ifdef EXEC_BACKEND
extern void SubPostmasterMain(int argc, char *argv[]) pg_attribute_noreturn();
#endif
Fix background workers for EXEC_BACKEND Commit da07a1e8 was broken for EXEC_BACKEND because I failed to realize that the MaxBackends recomputation needed to be duplicated by subprocesses in SubPostmasterMain. However, instead of having the value be recomputed at all, it's better to assign the correct value at postmaster initialization time, and have it be propagated to exec'ed backends via BackendParameters. MaxBackends stays as zero until after modules in shared_preload_libraries have had a chance to register bgworkers, since the value is going to be untrustworthy till that's finished. Heikki Linnakangas and Álvaro Herrera
2013-01-02 16:01:14 +01:00
/*
Allow Pin/UnpinBuffer to operate in a lockfree manner. Pinning/Unpinning a buffer is a very frequent operation; especially in read-mostly cache resident workloads. Benchmarking shows that in various scenarios the spinlock protecting a buffer header's state becomes a significant bottleneck. The problem can be reproduced with pgbench -S on larger machines, but can be considerably worse for queries which touch the same buffers over and over at a high frequency (e.g. nested loops over a small inner table). To allow atomic operations to be used, cram BufferDesc's flags, usage_count, buf_hdr_lock, refcount into a single 32bit atomic variable; that allows to manipulate them together using 32bit compare-and-swap operations. This requires reducing MAX_BACKENDS to 2^18-1 (which could be lifted by using a 64bit field, but it's not a realistic configuration atm). As not all operations can easily implemented in a lockfree manner, implement the previous buf_hdr_lock via a flag bit in the atomic variable. That way we can continue to lock the header in places where it's needed, but can get away without acquiring it in the more frequent hot-paths. There's some additional operations which can be done without the lock, but aren't in this patch; but the most important places are covered. As bufmgr.c now essentially re-implements spinlocks, abstract the delay logic from s_lock.c into something more generic. It now has already two users, and more are coming up; there's a follupw patch for lwlock.c at least. This patch is based on a proof-of-concept written by me, which Alexander Korotkov made into a fully working patch; the committed version is again revised by me. Benchmarking and testing has, amongst others, been provided by Dilip Kumar, Alexander Korotkov, Robert Haas. On a large x86 system improvements for readonly pgbench, with a high client count, of a factor of 8 have been observed. Author: Alexander Korotkov and Andres Freund Discussion: 2400449.GjM57CE0Yg@dinodell
2016-04-11 05:12:32 +02:00
* Note: MAX_BACKENDS is limited to 2^18-1 because that's the width reserved
* for buffer references in buf_internals.h. This limitation could be lifted
* by using a 64bit state; but it's unlikely to be worthwhile as 2^18-1
* backends exceed currently realistic configurations. Even if that limitation
* were removed, we still could not a) exceed 2^23-1 because inval.c stores
Replace BackendIds with 0-based ProcNumbers Now that BackendId was just another index into the proc array, it was redundant with the 0-based proc numbers used in other places. Replace all usage of backend IDs with proc numbers. The only place where the term "backend id" remains is in a few pgstat functions that expose backend IDs at the SQL level. Those IDs are now in fact 0-based ProcNumbers too, but the documentation still calls them "backend ids". That term still seems appropriate to describe what the numbers are, so I let it be. One user-visible effect is that pg_temp_0 is now a valid temp schema name, for backend with ProcNumber 0. Reviewed-by: Andres Freund Discussion: https://www.postgresql.org/message-id/8171f1aa-496f-46a6-afc3-c46fe7a9b407@iki.fi
2024-03-03 18:38:22 +01:00
* the ProcNumber as a 3-byte signed integer, b) INT_MAX/4 because some places
Allow Pin/UnpinBuffer to operate in a lockfree manner. Pinning/Unpinning a buffer is a very frequent operation; especially in read-mostly cache resident workloads. Benchmarking shows that in various scenarios the spinlock protecting a buffer header's state becomes a significant bottleneck. The problem can be reproduced with pgbench -S on larger machines, but can be considerably worse for queries which touch the same buffers over and over at a high frequency (e.g. nested loops over a small inner table). To allow atomic operations to be used, cram BufferDesc's flags, usage_count, buf_hdr_lock, refcount into a single 32bit atomic variable; that allows to manipulate them together using 32bit compare-and-swap operations. This requires reducing MAX_BACKENDS to 2^18-1 (which could be lifted by using a 64bit field, but it's not a realistic configuration atm). As not all operations can easily implemented in a lockfree manner, implement the previous buf_hdr_lock via a flag bit in the atomic variable. That way we can continue to lock the header in places where it's needed, but can get away without acquiring it in the more frequent hot-paths. There's some additional operations which can be done without the lock, but aren't in this patch; but the most important places are covered. As bufmgr.c now essentially re-implements spinlocks, abstract the delay logic from s_lock.c into something more generic. It now has already two users, and more are coming up; there's a follupw patch for lwlock.c at least. This patch is based on a proof-of-concept written by me, which Alexander Korotkov made into a fully working patch; the committed version is again revised by me. Benchmarking and testing has, amongst others, been provided by Dilip Kumar, Alexander Korotkov, Robert Haas. On a large x86 system improvements for readonly pgbench, with a high client count, of a factor of 8 have been observed. Author: Alexander Korotkov and Andres Freund Discussion: 2400449.GjM57CE0Yg@dinodell
2016-04-11 05:12:32 +02:00
* compute 4*MaxBackends without any overflow check. This is rechecked in the
* relevant GUC check hooks and in RegisterBackgroundWorker().
Fix background workers for EXEC_BACKEND Commit da07a1e8 was broken for EXEC_BACKEND because I failed to realize that the MaxBackends recomputation needed to be duplicated by subprocesses in SubPostmasterMain. However, instead of having the value be recomputed at all, it's better to assign the correct value at postmaster initialization time, and have it be propagated to exec'ed backends via BackendParameters. MaxBackends stays as zero until after modules in shared_preload_libraries have had a chance to register bgworkers, since the value is going to be untrustworthy till that's finished. Heikki Linnakangas and Álvaro Herrera
2013-01-02 16:01:14 +01:00
*/
Allow Pin/UnpinBuffer to operate in a lockfree manner. Pinning/Unpinning a buffer is a very frequent operation; especially in read-mostly cache resident workloads. Benchmarking shows that in various scenarios the spinlock protecting a buffer header's state becomes a significant bottleneck. The problem can be reproduced with pgbench -S on larger machines, but can be considerably worse for queries which touch the same buffers over and over at a high frequency (e.g. nested loops over a small inner table). To allow atomic operations to be used, cram BufferDesc's flags, usage_count, buf_hdr_lock, refcount into a single 32bit atomic variable; that allows to manipulate them together using 32bit compare-and-swap operations. This requires reducing MAX_BACKENDS to 2^18-1 (which could be lifted by using a 64bit field, but it's not a realistic configuration atm). As not all operations can easily implemented in a lockfree manner, implement the previous buf_hdr_lock via a flag bit in the atomic variable. That way we can continue to lock the header in places where it's needed, but can get away without acquiring it in the more frequent hot-paths. There's some additional operations which can be done without the lock, but aren't in this patch; but the most important places are covered. As bufmgr.c now essentially re-implements spinlocks, abstract the delay logic from s_lock.c into something more generic. It now has already two users, and more are coming up; there's a follupw patch for lwlock.c at least. This patch is based on a proof-of-concept written by me, which Alexander Korotkov made into a fully working patch; the committed version is again revised by me. Benchmarking and testing has, amongst others, been provided by Dilip Kumar, Alexander Korotkov, Robert Haas. On a large x86 system improvements for readonly pgbench, with a high client count, of a factor of 8 have been observed. Author: Alexander Korotkov and Andres Freund Discussion: 2400449.GjM57CE0Yg@dinodell
2016-04-11 05:12:32 +02:00
#define MAX_BACKENDS 0x3FFFF
Fix background workers for EXEC_BACKEND Commit da07a1e8 was broken for EXEC_BACKEND because I failed to realize that the MaxBackends recomputation needed to be duplicated by subprocesses in SubPostmasterMain. However, instead of having the value be recomputed at all, it's better to assign the correct value at postmaster initialization time, and have it be propagated to exec'ed backends via BackendParameters. MaxBackends stays as zero until after modules in shared_preload_libraries have had a chance to register bgworkers, since the value is going to be untrustworthy till that's finished. Heikki Linnakangas and Álvaro Herrera
2013-01-02 16:01:14 +01:00
Separate out bgwriter code into a logically separate module, rather than being random pieces of other files. Give bgwriter responsibility for all checkpoint activity (other than a post-recovery checkpoint); so this child process absorbs the functionality of the former transient checkpoint and shutdown subprocesses. While at it, create an actual include file for postmaster.c, which for some reason never had its own file before.
2004-05-30 00:48:23 +02:00
#endif /* _POSTMASTER_H */