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From: Christoph Hellwig <hch@lst.de>
To: Christophe Leroy <christophe.leroy@csgroup.eu>,
	Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-arch@vger.kernel.org, Kees Cook <keescook@chromium.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: iter and normal ops on /dev/zero & co, was Re: remove the last set_fs() in common code, and remove it for x86 and powerpc
Date: Wed, 19 Aug 2020 09:22:13 +0200	[thread overview]
Message-ID: <20200819072213.GA21832@lst.de> (raw)
In-Reply-To: <f2e31c89-dd9e-f0f8-ef5c-e930d01a3b65@csgroup.eu>

On Wed, Aug 19, 2020 at 09:16:59AM +0200, Christophe Leroy wrote:
> I made a test with only the first patch of your series: That's definitely 
> the culprit. With only that patch applies, the duration is 6.64 seconds, 
> that's a 25% degradation.

For the record: the first patch is:

     mem: remove duplicate ops for /dev/zero and /dev/null

So these micro-optimizations matter at least for some popular
benchmarks.  It would be easy to drop, but that means we either:

 - can't support kernel_read/write on these files, which should not
   matter

or
 
 - have to drop the check for both ops being present

Al, what do you think?

      reply	other threads:[~2020-08-19  7:22 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-17  7:32 remove the last set_fs() in common code, and remove it for x86 and powerpc Christoph Hellwig
2020-08-17  7:32 ` [PATCH 01/11] mem: remove duplicate ops for /dev/zero and /dev/null Christoph Hellwig
2020-08-18 19:33   ` Kees Cook
2020-08-17  7:32 ` [PATCH 02/11] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-08-18 19:34   ` Kees Cook
2020-08-17  7:32 ` [PATCH 03/11] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-08-18 19:39   ` Kees Cook
2020-08-18 19:54     ` Christoph Hellwig
2020-08-18 19:58       ` Kees Cook
2020-08-18 20:07         ` Christoph Hellwig
2020-08-17  7:32 ` [PATCH 04/11] uaccess: add infrastructure for kernel builds with set_fs() Christoph Hellwig
2020-08-18 19:40   ` Kees Cook
2020-08-17  7:32 ` [PATCH 05/11] test_bitmap: skip user bitmap tests for !CONFIG_SET_FS Christoph Hellwig
2020-08-17  7:50   ` Christophe Leroy
2020-08-17  7:52     ` Christoph Hellwig
2020-08-18 19:43   ` Kees Cook
2020-08-17  7:32 ` [PATCH 06/11] lkdtm: disable set_fs-based " Christoph Hellwig
2020-08-18 19:32   ` Kees Cook
2020-08-17  7:32 ` [PATCH 07/11] x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h Christoph Hellwig
2020-08-18 19:27   ` Kees Cook
2020-08-17  7:32 ` [PATCH 08/11] x86: make TASK_SIZE_MAX usable from assembly code Christoph Hellwig
2020-08-18 19:44   ` Kees Cook
2020-08-18 19:55     ` Christoph Hellwig
2020-08-18 19:59       ` Kees Cook
2020-08-18 20:00         ` Christoph Hellwig
2020-08-18 20:08           ` Kees Cook
2020-08-17  7:32 ` [PATCH 09/11] x86: remove address space overrides using set_fs() Christoph Hellwig
2020-08-17  8:23   ` David Laight
2020-08-27  9:37     ` 'Christoph Hellwig'
2020-08-18 19:46   ` Kees Cook
2020-08-17  7:32 ` [PATCH 10/11] powerpc: use non-set_fs based maccess routines Christoph Hellwig
2020-08-17 15:47   ` Christophe Leroy
2020-08-17  7:32 ` [PATCH 11/11] powerpc: remove address space overrides using set_fs() Christoph Hellwig
2020-08-17  7:39 ` remove the last set_fs() in common code, and remove it for x86 and powerpc Christoph Hellwig
2020-08-18 17:46 ` Christophe Leroy
2020-08-18 18:05   ` Christoph Hellwig
2020-08-18 18:23     ` Christophe Leroy
2020-08-19  7:16       ` Christophe Leroy
2020-08-19  7:22         ` Christoph Hellwig [this message]

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