From: Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>
To: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH] Linux: Use 32-bit vDSO for clock_gettime, gettimeofday, time (bug 28071)
Date: Mon, 12 Jul 2021 12:40:05 +0200 [thread overview]
Message-ID: <878s2bdddm.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <158cdbcb-5335-9ff4-cf3e-a45d8603d029@linaro.org> (Adhemerval Zanella's message of "Sat, 10 Jul 2021 17:30:08 -0300")
* Adhemerval Zanella:
> Using the test (a slight modified one from the bug report):
>
> --
> #include <time.h>
> #include <stdio.h>
> #include <errno.h>
>
> int
> main (void)
> {
> struct timespec ts;
> errno = 0;
> clock_gettime (CLOCK_REALTIME, &ts);
> printf ("errno = %m (%d)\n", errno);
> errno = 0;
> clock_gettime (CLOCK_MONOTONIC, &ts);
> printf ("errno = %m (%d)\n", errno);
> }
> --
>
> I see no syscall on 5.11 kernel, only a clock_gettime (CLOCK_MONOTONIC)
> on the 4.4 and a clock_gettime_time64 plus a clock_gettime on the 3.10.
This still introduces a severe performance regression on older kernels.
It may well make some exsting 32-bit applications unusable until the
kernel is upgraded. I'm not sure if this is a good idea.
At least I can see that the clobbering of errno is gone.
Thanks,
Florian
next prev parent reply other threads:[~2021-07-12 10:40 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-10 17:15 [PATCH] Linux: Use 32-bit vDSO for clock_gettime, gettimeofday, time (bug 28071) Florian Weimer via Libc-alpha
2021-07-10 18:22 ` Adhemerval Zanella via Libc-alpha
2021-07-10 18:54 ` Florian Weimer via Libc-alpha
2021-07-10 19:57 ` Adhemerval Zanella via Libc-alpha
2021-07-10 20:00 ` Florian Weimer via Libc-alpha
2021-07-10 20:03 ` Adhemerval Zanella via Libc-alpha
2021-07-10 20:30 ` Adhemerval Zanella via Libc-alpha
2021-07-12 10:40 ` Florian Weimer via Libc-alpha [this message]
2021-07-12 11:55 ` Adhemerval Zanella via Libc-alpha
2021-07-12 13:15 ` Florian Weimer via Libc-alpha
2021-07-12 14:20 ` Adhemerval Zanella via Libc-alpha
2021-07-12 14:29 ` Florian Weimer via Libc-alpha
2021-07-12 15:46 ` Adhemerval Zanella via Libc-alpha
2021-07-12 17:55 ` Florian Weimer via Libc-alpha
2021-07-12 18:00 ` Adhemerval Zanella via Libc-alpha
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