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Subject: Re: [PHP-DEV] Adding a way to disable the stat cache
From: cschneid@cschneid.com (Christian Schneider)

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Am 03.09.2021 um 18:12 schrieb Kevin Lyda <kevin@lyda.ie =
<mailto:kevin@lyda.ie>>:
> To run this php script:
>=20
> <?php
> $iterations =3D 1000000;
> function all_the_stats($filename) {
>   @lstat($filename);
>   @stat($filename);
> }
> while ($iterations--) {
>   all_the_stats(__FILE__);
> }
>=20
> I see this output:
>=20
> Without cache
>=20
> real 0m7.326s
> user 0m5.877s
> sys 0m1.448s
> With cache
>=20
> real 0m5.010s
> user 0m5.009s
> sys 0m0.000s

So this is almost a 50% performance regression ;-)
And the more interesting number for me here is "sys 0m1.448s" vs "sys =
0m0.000s". Which means 1.5s out of the additional 2.3s are spent in =
system calls.
Side-note: Why is the user time without cache higher than with cache? =
That seems counter-intuitive. Maybe the checking of the ini-settings or =
some libc-code?

I'm interested in the load put on a system with a high request count and =
a typical application.
Reducing system calls used to matter there as the kernel does not =
multi-process the same way user land does.

But then again, maybe I'm overly cautious :-)

Regards,
- Chris=

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