From: Ingo Molnar <mingo@kernel.org>
To: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Mike Snitzer <snitzer@redhat.com>,
dm-devel@redhat.com, linux-kernel@vger.kernel.org,
Mikulas Patocka <mpatocka@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>
Subject: Re: [PATCH 1/2] Revert "Revert "math64: New div64_u64_rem helper""
Date: Tue, 20 Aug 2013 10:09:10 +0200 [thread overview]
Message-ID: <20130820080910.GA11072@gmail.com> (raw)
In-Reply-To: <20130820070045.GA1665@redhat.com>
* Stanislaw Gruszka <sgruszka@redhat.com> wrote:
> On Fri, Aug 09, 2013 at 03:56:03PM -0400, Mike Snitzer wrote:
> > This reverts commit f3002134158092178be81339ec5a22ff80e6c308.
> >
> > div64_u64_rem was removed because there were no other users.
> >
> > But Device Mapper's I/O statistics support has a need for
> > div64_u64_rem; reintroduce this helper.
>
> This slows down div64_u64 operation, especially on 32-bit
> systems.
>
> Since dm statistic code is possibly not performance
> critical perhaps you could use something like below
> instead to calculate remainder:
>
> res = div64_u64(a, b);
> rem = a - b*res;
Or introduce a separately named helper without touching the
existing methods.
Thanks,
Ingo
next prev parent reply other threads:[~2013-08-20 8:09 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-09 19:56 [PATCH 1/2] Revert "Revert "math64: New div64_u64_rem helper"" Mike Snitzer
2013-08-09 19:56 ` [PATCH 2/2 v3] dm: add statistics support Mike Snitzer
2013-08-20 7:00 ` [PATCH 1/2] Revert "Revert "math64: New div64_u64_rem helper"" Stanislaw Gruszka
2013-08-20 8:09 ` Ingo Molnar [this message]
2013-08-20 19:25 ` Mike Snitzer
2013-08-21 7:21 ` Ingo Molnar
2013-08-21 15:09 ` [PATCH] math64: New separate div64_u64_rem helper Mike Snitzer
2013-09-04 16:11 ` [PATCH 1/2] Revert "Revert "math64: New div64_u64_rem helper"" Anatol Pomozov
2013-09-04 17:55 ` Mike Snitzer
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