From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: jgdr@dalibo.com
Cc: andres@anarazel.de
Cc: michael@paquier.xyz
Cc: sawada.mshk@gmail.com
Cc: peter.eisentraut@2ndquadrant.com
Cc: pgsql-hackers@lists.postgresql.org
Cc: thomas.munro@enterprisedb.com
Cc: sk@zsrv.org
Cc: michael.paquier@gmail.com
Subject: Re: [HACKERS] Restricting maximum keep segments by repslots
Date: Mon, 27 Apr 2020 19:40:07 -0400
Message-ID: <20200427234007.GA14631@alvherre.pgsql> (raw)
In-Reply-To: <20200408.164605.1874250940847340108.horikyota.ntt@gmail.com>
On 2020-Apr-08, Kyotaro Horiguchi wrote:
> I understand how it happens.
>
> The latch triggered by checkpoint request by CHECKPOINT command has
> been absorbed by ConditionVariableSleep() in
> InvalidateObsoleteReplicationSlots. The attached allows checkpointer
> use MyLatch for other than checkpoint request while a checkpoint is
> running.
Hmm, that explanation makes sense, but I couldn't reproduce it with the
steps you provided. Perhaps I'm missing something.
Anyway I think this patch should fix it also -- instead of adding a new
flag, we just rely on the existing flags (since do_checkpoint must have
been set correctly from the flags earlier in that block.)
I think it'd be worth to verify this bugfix in a new test. Would you
have time to produce that? I could try in a couple of days ...
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Attachments:
[text/x-diff] 0001-Don-t-freeze-on-checkpoints.patch (841B, ../20200427234007.GA14631@alvherre.pgsql/2-0001-Don-t-freeze-on-checkpoints.patch)
download | inline diff:
From 511c22043846c7453cea8b00bf911705417609eb Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Mon, 27 Apr 2020 19:35:15 -0400
Subject: [PATCH] Don't freeze on checkpoints
---
src/backend/postmaster/checkpointer.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.cindex e354a78725..5cf5e9fe08 100644--- a/src/backend/postmaster/checkpointer.c+++ b/src/backend/postmaster/checkpointer.c@@ -494,6 +494,13 @@ CheckpointerMain(void)
*/
pgstat_send_bgwriter();
+ /*+ * Don't sleep if our latch was set for reasons other than a+ * checkpoint request.+ */+ if (!do_checkpoint)+ continue;+
/*
* Sleep until we are signaled or it's time for another checkpoint or
* xlog file switch.
--
2.20.1
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To: pgsql-hackers@postgresql.org
Cc: alvherre@2ndquadrant.com, horikyota.ntt@gmail.com, jgdr@dalibo.com, andres@anarazel.de, michael@paquier.xyz, sawada.mshk@gmail.com, peter.eisentraut@2ndquadrant.com, pgsql-hackers@lists.postgresql.org, thomas.munro@enterprisedb.com, sk@zsrv.org, michael.paquier@gmail.com
Subject: Re: [HACKERS] Restricting maximum keep segments by repslots
In-Reply-To: <20200427234007.GA14631@alvherre.pgsql>
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