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From: Florian Weimer <fweimer@redhat.com>
To: Carlos O'Donell <carlos@redhat.com>
Cc: libc-alpha@sourceware.org
Subject: Re: [PATCH] malloc: Revert fastbins to old-style atomics
Date: Wed, 16 Jan 2019 16:33:03 +0100	[thread overview]
Message-ID: <87k1j4wrbk.fsf@oldenburg2.str.redhat.com> (raw)
In-Reply-To: <793fa38d-e8aa-4903-5dfd-7997d511c367@redhat.com> (Carlos O'Donell's message of "Wed, 16 Jan 2019 10:18:54 -0500")

* Carlos O'Donell:

> On 1/16/19 8:04 AM, Florian Weimer wrote:
>> Commit 6923f6db1e688dedcf3a6556da76e0bf24a41872 ("malloc: Use current
>> (C11-style) atomics for fastbin access") caused a substantial
>> performance regression on POWER and Aarch64, and the old atomics,
>> while hard to prove correct, seem to work in practice.
>
> Why is it slow?
>
> What do the benchmarks say?
>
> What does profiling show to be the slow instruction?
>
> How is the instruction sequence different from before that causes the
> problem?

The other thread is here:

  <https://sourceware.org/ml/libc-alpha/2019-01/msg00379.html>

Thanks,
Florian

  reply	other threads:[~2019-01-16 15:33 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 13:04 [PATCH] malloc: Revert fastbins to old-style atomics Florian Weimer
2019-01-16 15:18 ` Carlos O'Donell
2019-01-16 15:33   ` Florian Weimer [this message]
2019-01-16 15:47     ` Carlos O'Donell
2019-01-18 12:16       ` Florian Weimer
2019-01-18 18:39         ` Siddhesh Poyarekar
2019-01-18 21:41           ` Florian Weimer

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