From: David Rientjes <rientjes@google.com>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>, linux-mm@kvack.org
Subject: Re: [PATCH] mempool: add unlikely and likely hints
Date: Fri, 7 Mar 2014 12:54:45 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.02.1403071254220.23969@chino.kir.corp.google.com> (raw)
In-Reply-To: <alpine.LRH.2.02.1403070942090.12776@file01.intranet.prod.int.rdu2.redhat.com>
On Fri, 7 Mar 2014, Mikulas Patocka wrote:
> > What observable performance benefit have you seen with this patch and
> > with what architecture? Could we include some data in the changelog?
>
> None - you usually don't get observable performance benefit from
> microoptimizations like this.
>
> It may be that the cache line that the patch saves aliases some other
> important cache lines and then, the patch saves two cache line refills.
> Or, the saved cache line doesn't alias anything important and then the
> patch doesn't have any effect at all. It's not worth spending many days or
> weeks trying to recreate a situation when the code cache is used in such a
> way that the patch would help.
>
Not sure there's any benefit of merging the patch, then.
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next prev parent reply other threads:[~2014-03-07 20:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-06 22:15 Mikulas Patocka
2014-03-07 10:10 ` David Rientjes
2014-03-07 14:50 ` Mikulas Patocka
2014-03-07 20:54 ` David Rientjes [this message]
2014-03-07 21:15 ` Mikulas Patocka
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