| From: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
|---|---|
| To: | Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Mateusz Guzik <mjguzik(at)gmail(dot)com> |
| Subject: | snprintf.c hammering memset() |
| Date: | 2018-10-01 23:09:15 |
| Message-ID: | CAEepm=3VF=PUp2f8gU8fgZB22yPE_KBS0+e1AHAtQ=09schTHg@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hello hackers,
Mateusz Guzik was benchmarking PostgreSQL on FreeBSD investigating the
kqueue thread and complained off-list about a lot of calls to memset()
of size 256KB from dopr() in our snprintf.c code.
Yeah, that says:
PrintfArgType argtypes[NL_ARGMAX + 2];
...
MemSet(argtypes, 0, sizeof(argtypes));
PrintfArgType is an enum, and we define NL_ARGMAX as 16 if the OS
didn't already define it. On FreeBSD 11, NL_ARGMAX was defined as 99
in <limits.h>. On FreeBSD 12, it is defined as 65536... ouch. On a
Debian box I see it is 4096.
Is there any reason to use the OS definition here?
--
Thomas Munro
http://www.enterprisedb.com
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