| From: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
|---|---|
| To: | PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Performance degradation on concurrent COPY into a single relation in PG16. |
| Date: | 2023-07-03 02:59:38 |
| Message-ID: | CAD21AoDenr=g1rKTMJf8JXmVOJqwmrmjjqPRTR4aBxCoXzFO=w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Jul 3, 2023 at 11:55 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> After further investigation, the performance degradation comes from
> calling posix_fallocate() (called via FileFallocate()) and pwritev()
> (called via FileZero) alternatively depending on how many blocks we
> extend by. And it happens only on the xfs filesystem.
FYI, the attached simple C program proves the fact that calling
alternatively posix_fallocate() and pwrite() causes slow performance
on posix_fallocate():
$ gcc -o test test.c
$ time ./test test.1 1
total 200000
fallocate 200000
filewrite 0
real 0m1.305s
user 0m0.050s
sys 0m1.255s
$ time ./test test.2 2
total 200000
fallocate 100000
filewrite 100000
real 1m29.222s
user 0m0.139s
sys 0m3.139s
Regards,
--
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com
| Attachment | Content-Type | Size |
|---|---|---|
| test.c | text/x-c-code | 952 bytes |
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