From: Dan Williams <djbw@fb.com>
To: NeilBrown <neilb@suse.de>
Cc: linux-raid <linux-raid@vger.kernel.org>,
Kumar Sundararajan <kumar@fb.com>,
David Brown <david.brown@hesbynett.no>
Subject: Re: [PATCH] raid5: add support for rmw writes in raid6
Date: Tue, 30 Apr 2013 14:32:05 -0700 [thread overview]
Message-ID: <CAA9_cmd0kuynynwXmNN_0yf-Go1iy4LeqPhXx6pDbEo5kUV1AA@mail.gmail.com> (raw)
In-Reply-To: <20130429112957.4bd6cd71@notabene.brown>
On Sun, Apr 28, 2013 at 6:29 PM, NeilBrown <neilb@suse.de> wrote:
> On Fri, 26 Apr 2013 14:35:27 -0700 Dan Williams <djbw@fb.com> wrote:
[..]
> which looks odd as when that expands out, we add Q_old to Q_old and as '+'
> is 'xor', it disappears. Maybe you mean:
>
> Q_new = Q_sub + g^i * Di_new
> ??
>
> This is exactly the sort of thing I wanted to see, but I hoped it wouldn't
> confuse me like it seems to be doing :-)
Sorry, yes for completeness the approach includes all the modified
data blocks (Di...Dm) and zero pages for the unmodified blocks in the
gen_syndrome.
Q_sub = Q_old + g^i * Di_old ... + g^m * Dm_old + (zero blocks)
Q_new = Q_sub + g^i *Di_new ... + g^m * Dm_new + (zero blocks)
For David, we're using vector processing (SSE) in gen_syndrome()
rather than individual multiplications by table lookup.
--
Dan
next prev parent reply other threads:[~2013-04-30 21:32 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-18 0:56 [PATCH] raid5: add support for rmw writes in raid6 Dan Williams
2013-04-18 18:40 ` Dan Williams
2013-04-22 4:22 ` NeilBrown
2013-04-26 21:35 ` Dan Williams
2013-04-29 1:29 ` NeilBrown
2013-04-29 7:10 ` David Brown
2013-04-29 16:11 ` Kumar Sundararajan
2013-04-29 19:28 ` David Brown
2013-04-30 0:05 ` Dan Williams
2013-04-30 6:48 ` David Brown
2013-04-30 16:01 ` Kumar Sundararajan
2013-04-30 16:10 ` Kumar Sundararajan
2013-04-30 18:39 ` David Brown
2013-04-29 17:54 ` Kumar Sundararajan
2013-04-30 21:32 ` Dan Williams [this message]
2013-05-01 13:57 ` David Brown
2013-05-08 17:42 ` Dan Williams
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=CAA9_cmd0kuynynwXmNN_0yf-Go1iy4LeqPhXx6pDbEo5kUV1AA@mail.gmail.com \
--to=djbw@fb.com \
--cc=david.brown@hesbynett.no \
--cc=kumar@fb.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).