linux-kernel - Re: [RFC PATCH 0/2] raid5: 65% sequential-write performance improvement, stripe-queue take2

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	04 Jul 2007 13:41:26 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	neilb@...e.de, raziebe@...il.com, akpm@...ux-foundation.org,
	davidsen@....com, linux-kernel@...r.kernel.org,
	linux-raid@...r.kernel.org
Subject: Re: [RFC PATCH 0/2] raid5: 65% sequential-write performance improvement, stripe-queue take2

Dan Williams <dan.j.williams@...el.com> writes:

> The write performance numbers are better than I expected and would seem
> to address the concerns raised in the thread "Odd (slow) RAID
> performance"[2].  The read performance drop was not expected.  However,
> the numbers suggest some additional changes to be made to the queuing
> model.

Have you considered supporting copy-xor in MD for non accelerated
RAID? I've been looking at fixing the old dubious slow crufty x86 SSE
XOR functions. One thing I discovered is that it seems fairly
pointless to make them slower with cache avoidance when most of the data is
copied before anyways. I think much more advantage could be gotten by
supporting copy-xor because XORing during a copy should be nearly
free.

On the other hand ext3 write() also uses a cache avoiding copy now
and for the XOR it would need to load the data from memory again.
Perhaps this could be also optimized somehow (e.g. setting a flag
somewhere and using a normal copy for the RAID-5 case)

-Andi

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/