From: Ryan Cumming <bodnar42@phalynx.dhs.org>
To: Dave Jones <davej@suse.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [patch] Prefetching file_read_actor()
Date: Mon, 31 Dec 2001 12:40:19 -0800 [thread overview]
Message-ID: <E16L9EJ-0004Rf-00@phalynx> (raw)
In-Reply-To: <Pine.LNX.4.33.0112312045130.17274-100000@Appserv.suse.de>
In-Reply-To: <Pine.LNX.4.33.0112312045130.17274-100000@Appserv.suse.de>
On December 31, 2001 11:47, Dave Jones wrote:
> Completly puzzled right now. Moving the prefetching to copy_to_user
> (and doing the tlb preload & prefetching the whole chunk to be copied
> (or cachesize if smaller)) results in a performance drop instead of a win.
>
> My initial guess is that some of the callers of copy_to_user are
> doing something that is harmed the prefetching.
> (Maybe they are doing additional prefetch() calls)
Maybe syscalls that only have to move a very small chunk of data
(gettimeofday(2), for instance), are hurt because of the wasted bytes they
are prefetching after the intended data? Also, for sizes greater than 512,
copy_to_user will call mmx_copy_user, which might call mmx_memcpy, which does
prefetching already on x86 CPUs that support it.
-Ryan
next prev parent reply other threads:[~2001-12-31 20:40 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-31 3:32 [patch] Prefetching file_read_actor() Dave Jones
2001-12-31 5:44 ` Andrew Morton
2001-12-31 10:58 ` Manfred Spraul
2001-12-31 19:28 ` Andrew Morton
2001-12-31 19:47 ` Dave Jones
2001-12-31 20:40 ` Ryan Cumming [this message]
2002-01-01 10:29 ` Alan Cox
2002-01-01 12:45 ` Dave Jones
2002-01-01 15:26 ` Alan Cox
2002-01-01 10:30 ` Alan Cox
2002-01-01 11:08 ` Anton Blanchard
2001-12-31 20:31 ` Dave Jones
2001-12-31 13:00 ` Alan Cox
2001-12-31 12:50 ` Rik van Riel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=E16L9EJ-0004Rf-00@phalynx \
--to=bodnar42@phalynx.dhs.org \
--cc=davej@suse.de \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.