From: "H. Peter Anvin" <hpa@zytor.com>
To: David Brown <david@westcontrol.com>
Cc: NeilBrown <neilb@suse.de>, Chris Pearson <kermit4@gmail.com>,
linux-raid@vger.kernel.org
Subject: Re: with raid-6 any writes access all disks
Date: Tue, 01 Nov 2011 15:22:44 -0700 [thread overview]
Message-ID: <4EB07134.9080308@zytor.com> (raw)
In-Reply-To: <4EA956FE.3070504@westcontrol.com>
On 10/27/2011 06:05 AM, David Brown wrote:
>
> Where does it go wrong? Is it the automatic vectorisation with SSE,
> etc., that is still too limited with gcc? I have done very little work
> with x86/amd64 assembly (most of my experience is with microcontrollers
> rather than "big" processors), so I haven't tried looking at gcc's SSE
> code and comparing it to hand-optimised code.
>
The autovectorization isn't good enough to understand the tricks that
are necessary to get good performance. They require leaning pretty hard
on the instruction set.
-hpa
prev parent reply other threads:[~2011-11-01 22:22 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-26 21:01 with raid-6 any writes access all disks Chris Pearson
2011-10-26 21:23 ` Peter W. Morreale
2011-10-26 21:23 ` NeilBrown
2011-10-26 22:30 ` H. Peter Anvin
2011-10-27 9:29 ` David Brown
2011-10-27 12:22 ` H. Peter Anvin
2011-10-27 13:05 ` David Brown
2011-11-01 22:22 ` H. Peter Anvin [this message]
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=4EB07134.9080308@zytor.com \
--to=hpa@zytor.com \
--cc=david@westcontrol.com \
--cc=kermit4@gmail.com \
--cc=linux-raid@vger.kernel.org \
--cc=neilb@suse.de \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).