From: Ted Ts'o <tytso@mit.edu>
To: Zach Brown <zab@zabbo.net>
Cc: Dave Kleikamp <dave.kleikamp@oracle.com>, linux-fsdevel@vger.kernel.org
Subject: Re: [ATTEND] Attendance request
Date: Thu, 2 Feb 2012 15:58:43 -0500 [thread overview]
Message-ID: <20120202205843.GD1032@thunk.org> (raw)
In-Reply-To: <4F2AF737.9020106@zabbo.net>
On Thu, Feb 02, 2012 at 03:51:03PM -0500, Zach Brown wrote:
>
> Well, for that one blocking case in the submission path.
>
> I certainly understand the desire to just make things less painful in
> this case, but I do wonder if the long-term win is to sink resources
> into trying to get threads executings async op so that the code paths
> don't have to be butchered into state machines around each potential
> blocking op.
I only intend to do this for reads and non-allocating writes; in those
cases, it's actually pretty easy. And if everything is already in
cache, it's a lot easier to make things fast and not require diving
into workqueue or some other kernel thread.
My concern with just stuffing every single io_submit into a kernel
thread is the overhead involved, especially if there is a high rate of
AIO submission (think high-speed PCIe-attached flash). Either you
will end up blocking waiting for a kernel thread to be available, or
you will burn a huge amount of kernel memory for the thread stacks if
nothing else.
- Ted
next prev parent reply other threads:[~2012-02-02 20:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-02 16:51 [ATTEND] Attendance request Dave Kleikamp
2012-02-02 19:00 ` Zach Brown
2012-02-02 19:07 ` Dave Kleikamp
2012-02-02 20:29 ` Ted Ts'o
2012-02-02 20:51 ` Zach Brown
2012-02-02 20:58 ` Ted Ts'o [this message]
2012-02-02 21:03 ` Zach Brown
2012-02-03 2:20 ` Zheng Liu
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