From: Theodore Ts'o <tytso@mit.edu>
To: "Cristian Rodríguez" <crrodriguez@opensuse.org>
Cc: linux-ext4@vger.kernel.org
Subject: Re: [PATCH] lib/ext2fs: Use __builtin_popcount when available Signed-off-by: Cristian Rodríguez <crrodriguez@opensuse.org>
Date: Sun, 6 Jan 2013 20:31:56 -0500 [thread overview]
Message-ID: <20130107013156.GB12838@thunk.org> (raw)
In-Reply-To: <50EA1C9B.8040304@opensuse.org>
On Sun, Jan 06, 2013 at 09:53:47PM -0300, Cristian Rodríguez wrote:
>
> Yeah, I asked GCC developers exactly this, was told to fill a
> enhancement request.
If you could also sned them a bug/enhancement request to use a more
optimized version of __popcountdi2, that would be great. I'm not sure
it helps e2fsprogs much, since it's too hard for us to tell whether we
are using a version of the gcc runtime that has a optimized or
unuptomized version of builtin_popcount().
But since it doesn't make that much difference, my preference is to
just ignore builtin_popcount() for now. If someone is really using
128TB ext4 file systems, and cares about that extra 6 seconds of CPU,
it's probably going to require the ugly approach of using x86 asm
statements to determine whether or not we're running on a CPU that
supports the popcount instruction or not....
- Ted
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next prev parent reply other threads:[~2013-01-07 1:32 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-06 15:04 [PATCH] lib/ext2fs: Use __builtin_popcount when available Signed-off-by: Cristian Rodríguez <crrodriguez@opensuse.org> Cristian Rodríguez
2013-01-06 22:20 ` Theodore Ts'o
2013-01-07 0:53 ` Cristian Rodríguez
2013-01-07 1:31 ` Theodore Ts'o [this message]
2013-01-07 1:46 ` Cristian Rodríguez
2013-01-07 1:56 ` Theodore Ts'o
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