linux-kernel - IOsched: AS improvements (was: [Announce] [patch] Modular Scheduler Core and Completely Fair)

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>] [day] [month] [year] [list]

Message-Id: <200704161029.18023.a1426z@gawab.com>
Date:	Mon, 16 Apr 2007 10:29:17 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	linux-kernel@...r.kernel.org
Subject: IOsched: AS improvements (was: [Announce] [patch] Modular Scheduler Core and Completely Fair)

Nick Piggin wrote:
> Actually, I would still like to be able to deprecate deadline for
> AS, because AS has a tunable that you can switch to turn off read
> anticipation and revert to deadline behaviour (or very close to).

You mean antic_expire?  I tried it, and it does have an enormous effect on 
performance.  Smaller values do mimic deadline behavior in a way, as 
deadline has some strange behaviour on sync, so it's closer to noop, which 
is good for single user/proc access, while larger values are good for multi 
user/proc access.  But I always have to set it to 0, or else it starves sync 
with others reading.

I wonder if these tunables couldn't be autotuned by some form of 
history-based access pattern detection?

> It would have been nice if CFQ were then a layer on top of AS that
> implemented priorities (or vice versa). And then AS could be
> deprecated and we'd be back to 1 primary scheduler.
>
> Well CFQ seems to be going in the right direction with that, however
> some large users still find AS faster for some reason...

AS is faster no-contest.  CFQ has some deep block-io/queue problem that slows 
it down up to 25%.  It's related to max_sectors_kb and read_ahead_kb , and I 
mentioned this to Jens before, and AS show this problem sometimes too, but 
with CFQ it's much more prevalent.

Thanks!

--
Al

-
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/