linux-kernel - Re: [RFC][PATCH 0/3] Skip I/O merges when disabled

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <87ve27gz4u.fsf@basil.nowhere.org>
Date:	Thu, 24 Apr 2008 15:29:05 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	"Alan D. Brunelle" <Alan.Brunelle@...com>
Cc:	linux-kernel@...r.kernel.org, Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [RFC][PATCH 0/3] Skip I/O merges when disabled

"Alan D. Brunelle" <Alan.Brunelle@...com> writes:

> The block I/O + elevator + I/O scheduler code spends a lot of time
> trying to merge I/Os -- rightfully so under "normal" circumstances.
> However, if one were to know that the incoming I/O stream was /very/
> random in nature, the cycles are wasted. (This can be the case, for
> example, during OLTP-type runs.)
>
> This patch stream adds a per-request_queue tunable that (when set)
> disables merge attempts, thus freeing up a non-trivial amount of CPU cycles.

It sounds interesting. But explicit tunables are always bad because
they will be only used by a elite few. Do you think it would be
possible instead to keep some statistics on how successfull merging is and
when the success rate is very low disable it automatically for some
time until a time out?

This way nearly everybody could get most of the benefit from this
change.

-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/