Re: POC: Cache data in GetSnapshotData()

On May 20, 2015 at 8:57 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>

wrote:

> +1 to proceed with this patch for 9.6, as I think this patch improves the

> situation with compare to current.

> Also I have seen crash once in below test scenario:

> Crashed in test with scale-factor - 300, other settings same as above:

> ./pgbench -c 128 -j 128 -T 1800 -M prepared postgres

I have rebased the patch and tried to run pgbench.

I see memory corruptions, attaching the valgrind report for the same.

First interesting callstack in valgrind report is as below.

==77922== For counts of detected and suppressed errors, rerun with: -v

==77922== Use --track-origins=yes to see where uninitialised values come
from

==77922== ERROR SUMMARY: 15 errors from 7 contexts (suppressed: 2 from 2)

==77873== Source and destination overlap in memcpy(0x5c08020, 0x5c08020, 4)

==77873== at 0x4C2E1DC: memcpy@@GLIBC_2.14 (in
/usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)

==77873== by 0x773303: GetSnapshotData (procarray.c:1698)

==77873== by 0x90FDB8: GetTransactionSnapshot (snapmgr.c:248)

==77873== by 0x79A22F: PortalStart (pquery.c:506)

==77873== by 0x795F67: exec_bind_message (postgres.c:1798)

==77873== by 0x798DDC: PostgresMain (postgres.c:4078)

==77873== by 0x724B27: BackendRun (postmaster.c:4237)

==77873== by 0x7242BB: BackendStartup (postmaster.c:3913)

==77873== by 0x720CF9: ServerLoop (postmaster.c:1684)

==77873== by 0x720380: PostmasterMain (postmaster.c:1292)

==77873== by 0x67CC9D: main (main.c:223)

==77873==

==77873== Source and destination overlap in memcpy(0x5c08020, 0x5c08020, 4)

==77873== at 0x4C2E1DC: memcpy@@GLIBC_2.14 (in
/usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)

==77873== by 0x77304A: GetSnapshotData (procarray.c:1579)

==77873== by 0x90FD75: GetTransactionSnapshot (snapmgr.c:233)

==77873== by 0x795A2F: exec_bind_message (postgres.c:1613)

==77873== by 0x798DDC: PostgresMain (postgres.c:4078)

==77873== by 0x724B27: BackendRun (postmaster.c:4237)

==77873== by 0x7242BB: BackendStartup (postmaster.c:3913)

==77873== by 0x720CF9: ServerLoop (postmaster.c:1684)

==77873== by 0x720380: PostmasterMain (postmaster.c:1292)

==77873== by 0x67CC9D: main (main.c:223)

--
Thanks and Regards
Mithun C Y
EnterpriseDB: http://www.enterprisedb.com