From: Maxim Orlov <m.orlov@postgrespro.ru>
To: Greg Nancarrow <gregn4422@gmail.com>
Cc: Pavel Borisov <pashkin.elfe@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>
Cc: Pengchengliu <pengchengliu@tju.edu.cn>
Cc: Andres Freund <andres@anarazel.de>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Parallel scan with SubTransGetTopmostTransaction assert coredump
Date: Fri, 04 Jun 2021 15:30:15 +0300
Message-ID: <09788181118f7bd8000d3bb097e0720f@postgrespro.ru> (raw)
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Just a note here. After examining the core dump I did notice something.
While in XidInMVCCSnapshot call the snapshot->suboverflowed is set true
although subxip == NULL and subxcnt == 0. As far as I understand,
snapshot->suboverflowed is set true in the GetRunningTransactionData
call.
And then I decided to put elog around CurrentRunningXacts->subxcnt's
assigment.
diff --git a/src/backend/storage/ipc/procarray.c
b/src/backend/storage/ipc/procarray.c
index 42a89fc5dc9..3d2db02f580 100644
--- a/src/backend/storage/ipc/procarray.c+++ b/src/backend/storage/ipc/procarray.c
@@ -2781,6 +2781,9 @@ GetRunningTransactionData(void)
* increases if slots do.
*/
+ if (suboverflowed)
+ elog(WARNING, " >>> CurrentRunningXacts->subxid_overflow
is true");
+
CurrentRunningXacts->xcnt = count - subcount;
CurrentRunningXacts->subxcnt = subcount;
CurrentRunningXacts->subxid_overflow = suboverflowed;
... and did get a bunch of messages. I.e. subxid_overflow is set true
very often.
I've increased the value of PGPROC_MAX_CACHED_SUBXIDS. Once it becomes
more than 120 there are no messages and no failed assertions are
provided any more.
---
Best regards,
Maxim Orlov.
Attachments:max-cached-subxibds.patch (text/x-diff, 1015B) downloaddiff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.cindex 42a89fc5dc9..3d2db02f580 100644--- a/src/backend/storage/ipc/procarray.c+++ b/src/backend/storage/ipc/procarray.c@@ -2781,6 +2781,9 @@ GetRunningTransactionData(void)
* increases if slots do.
*/
+ if (suboverflowed)+ elog(WARNING, " >>> CurrentRunningXacts->subxid_overflow is true");+
CurrentRunningXacts->xcnt = count - subcount;
CurrentRunningXacts->subxcnt = subcount;
CurrentRunningXacts->subxid_overflow = suboverflowed;
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.hindex be67d8a8616..8e1a3d1c6bb 100644--- a/src/include/storage/proc.h+++ b/src/include/storage/proc.h@@ -33,7 +33,7 @@
* listed anywhere in the PGPROC array is not a running transaction. Else we
* have to look at pg_subtrans.
*/
-#define PGPROC_MAX_CACHED_SUBXIDS 64 /* XXX guessed-at value */+#define PGPROC_MAX_CACHED_SUBXIDS 120 /* XXX guessed-at value */
typedef struct XidCacheStatus
{
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To: pgsql-hackers@postgresql.org
Cc: m.orlov@postgrespro.ru, gregn4422@gmail.com, pashkin.elfe@gmail.com, michael@paquier.xyz, pengchengliu@tju.edu.cn, andres@anarazel.de
Subject: Re: Parallel scan with SubTransGetTopmostTransaction assert coredump
In-Reply-To: <09788181118f7bd8000d3bb097e0720f@postgrespro.ru>
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