From: "Hua Zhong" <hzhong@gmail.com>
To: "'Jens Axboe'" <axboe@suse.de>
Cc: <linux-kernel@vger.kernel.org>, <akpm@osdl.org>
Subject: RE: [PATCH] likely cleanup: revert unlikely in ll_back_merge_fn
Date: Tue, 25 Apr 2006 14:38:58 -0700 [thread overview]
Message-ID: <004d01c668b0$a9c79540$853d010a@nuitysystems.com> (raw)
In-Reply-To: <20060425183026.GR4102@suse.de>
It seems that new BIOs do not have BIO_SEG_VALID set. So when you do sequential IO, the IO being back-merged should always have not
had valid segments.
I ran bonnie++ and it shows the same thing.
> Well you'd want to optimize for the busy case, right, no
> point in optimizing for a more idle system.
>
> I'm not at all uninterested in this, I'd just like to see a
> more intelligent/controlled work load that actually stresses
> the io subsystem being profiled. If you have a not-so-busy
> system, you like don't do enough IO to trigger a lot of
> merges. Or maybe you do, and we just have a bug somewhere so
> that we unfortunately repeatedly recount segments.
>
> Care to run a simple io benchmark and profile that?
>
> --
> Jens Axboe
>
next prev parent reply other threads:[~2006-04-25 21:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-25 18:18 [PATCH] likely cleanup: revert unlikely in ll_back_merge_fn Hua Zhong
2006-04-25 18:30 ` Jens Axboe
2006-04-25 21:38 ` Hua Zhong [this message]
2006-04-26 5:20 ` Jens Axboe
2006-04-26 13:50 ` James Bottomley
2006-04-26 13:55 ` Jens Axboe
2006-04-26 14:24 ` James Bottomley
2006-04-27 14:39 ` Jens Axboe
2006-04-26 17:06 ` Hua Zhong
2006-04-30 19:25 ` Pavel Machek
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