From: Zachary Amsden <zamsden@redhat.com>
To: Pavel Machek <pavel@ucw.cz>
Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
axboe@kernel.dk, hch@infradead.org, akpm@linux-foundation.org,
Paul.Clements@steeleye.com, tytso@mit.edu
Subject: Re: [PATCH] Allow userspace block device implementation
Date: Mon, 10 Aug 2009 12:47:24 -1000 [thread overview]
Message-ID: <4A80A37C.9000808@redhat.com> (raw)
In-Reply-To: <20090807180841.GC1728@ucw.cz>
Pavel Machek wrote:
> Hi!
Hey!
> And yes, I believe that's show stopper. OTOH if you _can_ solve
> that... then you have some rather significant advantage over nbd.
>
> (But guaranteeing progress for dirty writeout will be tricky even with
> mlocked userland, AFAICT...)
Actually, impossible, even with mlocked userland (*) which is what led
me to abandon going any further with it. The problem is, to commit any
data, one must make a system call, thus consuming more resources. It's
merely a toy, nothing more. Sometimes it might be a useful toy, as nbd,
but nbd, being in kernel, has at least a better chance of solving the
swap problem.
(*) strictly speaking, it is possible to guarantee progress of the
device for read/write only to a finite region of mlocked memory and an
infinite region (limited only by size of off_t) of read-only data
computable with finite mlocked space. Obviously, neither of these
(swap-to-ram), and (swap-over-ro-media) are actually useful for swap.
Zach
next prev parent reply other threads:[~2009-08-10 22:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-27 9:57 [PATCH] Allow userspace block device implementation Zachary Amsden
2009-07-27 12:56 ` Peter Zijlstra
2009-07-27 13:25 ` Alan Cox
2009-07-27 19:46 ` Zachary Amsden
2009-07-27 20:24 ` Peter Zijlstra
2009-07-27 21:02 ` Alan Cox
2009-07-28 1:21 ` Tejun Heo
2009-07-28 3:53 ` Zachary Amsden
2009-07-28 10:27 ` Alan Cox
2009-07-28 16:00 ` Linus Torvalds
2009-07-28 18:36 ` Kyle Moffett
2009-07-28 18:51 ` Linus Torvalds
2009-07-28 19:07 ` Alan Cox
2009-07-28 19:49 ` Andi Kleen
2009-07-28 20:50 ` Linus Torvalds
2009-07-28 21:09 ` Andi Kleen
2009-07-28 22:56 ` Theodore Tso
2009-08-07 18:08 ` Pavel Machek
2009-08-10 22:47 ` Zachary Amsden [this message]
-- strict thread matches above, loose matches on Subject: below --
2009-07-28 20:37 devzero
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