| From: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> |
|---|---|
| To: | tgl(at)sss(dot)pgh(dot)pa(dot)us |
| Cc: | thomas(dot)munro(at)gmail(dot)com, pg(at)bowt(dot)ie, pgsql-hackers(at)lists(dot)postgresql(dot)org, craig(dot)ringer(at)enterprisedb(dot)com, robertmhaas(at)gmail(dot)com |
| Subject: | Re: 011_crash_recovery.pl intermittently fails |
| Date: | 2021-03-05 07:51:17 |
| Message-ID: | 20210305.165117.1192284154251506643.horikyota.ntt@gmail.com |
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| Lists: | pgsql-hackers |
At Thu, 04 Mar 2021 23:40:34 -0500, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote in
> BTW, I tried simply removing the "allows_streaming" option from
> the test, and it failed ten times out of ten tries for me.
> So Andres is right that that makes it pretty reproducible in
> a stock build.
The difference comes from the difference of shared_buffers. In the
"allows_streaming" case, PostgresNode::init() *reduces* the number
down to '1MB'(128 blocks) which leads to only 8 XLOGbuffers, which
will very soon be wrap-arounded, which leads to XLogWrite.
When allows_streaming=0 case, the default size of shared_buffers is
128MB (16384 blocks). WAL buffer (512) doesn't get wrap-arounded
during the test and no WAL buffer is written out in that case.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
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