Re: checkpointer continuous flushing

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: checkpointer continuous flushing
Date: 2015-07-26 15:01:50
Message-ID: alpine.DEB.2.10.1507261656380.25082@sto
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Attached is very minor v5 update which does a rebase & completes the
cleanup of doing a full sort instead of a chuncked sort.

>> Attached is an updated version of the patch which turns the sort option
>> into a boolean, and also include the sort time in the checkpoint log.
>> There is still an open question about whether the sorting buffer allocation
>> is lost on some signals and should be reallocated in such event.
> In such case, probably the allocation should be managed from
> CheckpointerMain, and the lazy allocation could remain for other callers (I
> guess just "initdb").
> More open questions:
> - best name for the flush option (checkpoint_flush_to_disk,
> checkpoint_flush_on_write, checkpoint_flush, ...)
> - best name for the sort option (checkpoint_sort,
> checkpoint_sort_buffers, checkpoint_sort_ios, ...)
> Other nice-to-have inputs:
> - tests on a non-linux system with posix_fadvise
> (FreeBSD? others?)
> - tests on a large dedicated box
> Attached are some scripts to help with testing, if someone's feels like that:
> - run some tests, to adapt to one's setup...
> - show percent of late transactions
> - show stats about stuff
> sh> grep 'progress: ' OUTPUT_FILE | cut -d' ' -f4 |
> *BEWARE* that if pgbench got stuck some "0" data are missing,
> look for the actual tps in the output file and for the line
> count to check whether it is the case... some currently submitted
> patch on pgbench helps, see

As this pgbench patch is now in master, pgbench is less likely to get
stuck, but check nevertheless that the number of progress line matches the
expected number.


Attachment Content-Type Size
checkpoint-continuous-flush-5.patch text/x-diff 42.5 KB

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