Hi Andres, Thomas,
Here is a patch for enabling SystemV Shared Memory on AIX, for 64K or bigger
page size, rather than using MMAP shared memory, which is slower on AIX.
We have tested this code with 64K pages and pgbench, on AIX 7.2 TL2 Power 9,
and it provided a maximum of +37% improvement.
We'll test this code with Large Pages (SHM_LGPAGE | SHM_PIN | S_IRUSR | S_IWUSR
flags of shmget() ) ASAP.
However, I wanted first to get your comments about this change in order to
improve it for acceptance.
Thanks/Regards,
Cordialement,
Tony Reix
tony.r...@atos.net
ATOS / Bull SAS
ATOS Expert
IBM Coop Architect & Technical Leader
Office : +33 (0) 4 76 29 72 67
1 rue de Provence - 38432 Échirolles - France
www.atos.net<https://mail.ad.bull.net/owa/redir.aspx?C=PvphmPvCZkGrAgHVnWGsdMcDKgzl_dEIsM6rX0g4u4v8V81YffzBGkWrtQeAXNovd3ttkJL8JIc.&URL=http%3a%2f%2fwww.atos.net%2f>
________________________________
De : REIX, Tony
Envoyé : mercredi 21 novembre 2018 09:45:12
À : Thomas Munro; Andres Freund
Cc : Robert Haas; Pg Hackers; EMPEREUR-MOT, SYLVIE; BERGAMINI, DAMIEN
Objet : RE: Shared Memory: How to use SYSV rather than MMAP ?
Hi Thomas, Andres,
I still have to reread/study in depth the discussion in this thread in order to
understand all these information. However, we've already got a very good
performance improvement of pgbench on AIX 7.2 / Power9 with that change: + ~38%
in best case. See below for the details.
This +38% improvement has been measured by comparison with a PostgreSQL v11.1
code which was built with: XLC -O2 + power9-tuning, plus some changes about
inlining for AIX and some fixes dealing with issues with XLC and PostgreSQL
#ifdef. Maybe GCC provides better results, we'll know later.
Once we are done with this performance analysis campaign, I'll have to submit
patches.
Meanwhile, if anyone has ideas about where the choices made for PostgreSQL on
Linux may have an impact to the performance on AIX, I'm very interested!
Regards,
Tony
Changes in PostgreSQL11.1 sources for SYSV large pages (64K) support :
* Main shared memory segment in sysv_shmem.c
removal of #define USE_ANONYMOUS_SHMEM
* Dynamic shared memory implementations in src/include/storage/dsm_impl.h :
#define USE_DSM_POSIX
// #define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_POSIX
#define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_SYSV
#endif
* Changes in PostgreSQL11.1 XCOFF binary with ledit :
* ldedit -btextpsize=64K -bdatapsize=64K -bstackpsize=64K
/opt/freeware/bin/postgres_64
* Env variable LDR_CNTRL=SHMPSIZE=64K
Cordialement,
Tony Reix
tony.r...@atos.net
ATOS / Bull SAS
ATOS Expert
IBM Coop Architect & Technical Leader
Office : +33 (0) 4 76 29 72 67
1 rue de Provence - 38432 Échirolles - France
www.atos.net<https://mail.ad.bull.net/owa/redir.aspx?C=PvphmPvCZkGrAgHVnWGsdMcDKgzl_dEIsM6rX0g4u4v8V81YffzBGkWrtQeAXNovd3ttkJL8JIc.&URL=http%3a%2f%2fwww.atos.net%2f>
--- ./src/backend/port/sysv_shmem.c.ORIGIN 2018-11-23 11:05:31 +0100
+++ ./src/backend/port/sysv_shmem.c 2018-11-23 11:16:04 +0100
@@ -63,9 +63,14 @@
* developer use, this shouldn't be a big problem. Because of this, we do
* not worry about supporting anonymous shmem in the EXEC_BACKEND cases below.
*/
+#if !defined(_AIX)
#ifndef EXEC_BACKEND
#define USE_ANONYMOUS_SHMEM
#endif
+// On AIX, 64K pages can be used only with SysV shared memory.
+// Not defining USE_ANONYMOUS_SHMEM on AIX leads to SysV shared memory.
+#endif
+
typedef key_t IpcMemoryKey; /* shared memory key passed to shmget(2) */
@@ -125,7 +130,13 @@
}
#endif
- shmid = shmget(memKey, size, IPC_CREAT | IPC_EXCL | IPCProtection);
+ shmid = shmget(memKey, size, IPC_CREAT | IPC_EXCL | IPCProtection
+#if !defined(_AIX)
+ );
+#else
+ // On AIX, SHM_LGPAGE & SHM_PIN are required in order to be able to use Large Pages
+ | SHM_LGPAGE | SHM_PIN | S_IRUSR | S_IWUSR);
+#endif
if (shmid < 0)
{
@@ -155,7 +166,13 @@
*/
if (shmget_errno == EINVAL)
{
- shmid = shmget(memKey, 0, IPC_CREAT | IPC_EXCL | IPCProtection);
+ shmid = shmget(memKey, 0, IPC_CREAT | IPC_EXCL | IPCProtection
+#if !defined(_AIX)
+ );
+#else
+ // On AIX, SHM_LGPAGE & SHM_PIN are required in order to be able to use Large Pages
+ | SHM_LGPAGE | SHM_PIN | S_IRUSR | S_IWUSR);
+#endif
if (shmid < 0)
{
--- ./src/include/storage/dsm_impl.h.ORIGIN 2018-11-23 11:33:45 +0100
+++ ./src/include/storage/dsm_impl.h 2018-11-23 11:34:40 +0100
@@ -30,7 +30,12 @@
#else
#ifdef HAVE_SHM_OPEN
#define USE_DSM_POSIX
+#if !defined(_AIX)
#define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_POSIX
+#else
+// On AIX, 64K pages can be used only with SysV shared memory
+#define DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE DSM_IMPL_SYSV
+#endif // AIX
#endif
#define USE_DSM_SYSV
#ifndef DEFAULT_DYNAMIC_SHARED_MEMORY_TYPE
