Re: Fix checkpoint skip logic on idle systems by tracking LSN progress

From: David Steele <david(at)pgmasters(dot)net>
To: Stephen Frost <sfrost(at)snowman(dot)net>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Fix checkpoint skip logic on idle systems by tracking LSN progress
Date: 2016-11-10 17:33:36
Message-ID: 74b0e04f-7b53-3ce4-e90b-10f7c738fd68@pgmasters.net
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On 11/10/16 10:28 AM, Stephen Frost wrote:

>> diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
> [...]
>> + if (log_checkpoints)
>> + ereport(LOG, (errmsg("checkpoint skipped")));
>
> Do we really need to log that we're skipping a checkpoint..? As the
> point of this is to avoid write activity on a system which is idle, it
> doesn't make sense to me to add a new cause for writes to happen when
> we're idle.

log_checkpoints is not enabled by default, though, so if the user does
enable it don't you think they would want to know when checkpoints
*don't* happen?

Or are you thinking the main use of this logging is to determine when
checkpoints are too close together and so skipped checkpoints aren't
very important?

Thanks,
--
-David
david(at)pgmasters(dot)net

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