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 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.