From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Florian Weimer <fweimer@redhat.com>
Cc: Paul Eggert <eggert@cs.ucla.edu>,
Adhemerval Zanella via Libc-alpha <libc-alpha@sourceware.org>,
crrodriguez@opensuse.org
Subject: Re: [PATCH 1/4] Remove architecture specific sched_cpucount optimizations
Date: Thu, 6 May 2021 13:54:46 -0300 [thread overview]
Message-ID: <6c3cc84c-4e02-d0ec-76ea-461b8a6f4a8c@linaro.org> (raw)
In-Reply-To: <87wnsbg6eu.fsf@oldenburg.str.redhat.com>
On 06/05/2021 13:42, Florian Weimer wrote:
> * Adhemerval Zanella:
>
>>> I get that choosing the exact matching builtin for the __cpu_mask type
>>> isn't easy, but wouldn't it be safe to use __builtin_popcountll
>>> unconditionally?
>>
>> Using a open-coded routine is slight better for architectures that
>> do not have a popcount instruction, since __builtin_popcountll will
>> call the libgcc routine). But I hardly think we need that amount
>> of micro-optimization for such routine.
>
> Ahh, and we'll get a check-localplt failure. Hmm. So mention that in
> the comment?
The check-localplt issue only occurs when using compiler generated symbols
if the libgcc function itself calls a glibc symbol (for instance arm div
soft-fp might call raise). In this case the call will be local, the
issue is more performance-wise.
next prev parent reply other threads:[~2021-05-06 16:54 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-29 18:25 Adhemerval Zanella
2021-03-29 18:25 ` [PATCH 2/4] linux: Use sched_getaffinity for __get_nprocs (BZ #27645) Adhemerval Zanella
2021-04-27 15:38 ` Florian Weimer
2021-03-29 18:25 ` [PATCH 3/4] linux: Use /sys/devices/system/cpu/possible on __get_nprocs_conf Adhemerval Zanella
2021-05-05 16:53 ` Adhemerval Zanella
2021-05-05 17:54 ` Florian Weimer
2021-05-05 18:06 ` Florian Weimer
2021-05-06 13:03 ` Adhemerval Zanella
2021-05-06 13:51 ` Florian Weimer
2021-05-06 20:07 ` Adhemerval Zanella
2021-05-07 11:07 ` Florian Weimer
2021-05-07 12:43 ` Adhemerval Zanella
2021-05-06 13:17 ` Adhemerval Zanella
2021-03-29 18:25 ` [PATCH 4/4] linux: Remove /proc/cpuinfo fallback on alpha and sparc Adhemerval Zanella
2021-05-05 16:53 ` Adhemerval Zanella
2021-05-05 16:52 ` [PATCH 1/4] Remove architecture specific sched_cpucount optimizations Adhemerval Zanella
2021-05-05 17:28 ` Florian Weimer
2021-05-05 18:25 ` Paul Eggert
2021-05-05 19:52 ` Noah Goldstein
2021-05-06 12:22 ` Adhemerval Zanella
2021-05-06 18:34 ` Noah Goldstein
2021-05-06 13:33 ` Adhemerval Zanella
2021-05-06 13:43 ` Florian Weimer
2021-05-06 16:16 ` Adhemerval Zanella
2021-05-06 16:42 ` Florian Weimer
2021-05-06 16:54 ` Adhemerval Zanella [this message]
2021-05-06 17:12 ` Paul Eggert
2021-05-06 17:51 ` Adhemerval Zanella
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