From: David Miller <davem@davemloft.net>
To: fujita.tomonori@lab.ntt.co.jp
Cc: mpatocka@redhat.com, sparclinux@vger.kernel.org,
linux-kernel@vger.kernel.org, jens.axboe@oracle.com
Subject: Re: [SUGGESTION]: drop virtual merge accounting in I/O requests
Date: Fri, 11 Jul 2008 12:41:52 -0700 (PDT) [thread overview]
Message-ID: <20080711.124152.247767508.davem@davemloft.net> (raw)
In-Reply-To: <20080711201558J.fujita.tomonori@lab.ntt.co.jp>
From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Date: Fri, 11 Jul 2008 20:15:52 +0900
> On Fri, 11 Jul 2008 06:52:09 -0400 (EDT)
> Mikulas Patocka <mpatocka@redhat.com> wrote:
>
> > On Fri, 11 Jul 2008, FUJITA Tomonori wrote:
> >
> > > Yeah, IOMMUs can't guarantee that. The majority of architectures set
> > > BIO_VMERGE_BOUNDARY to 0 so they don't hit this, I think.
> >
> > Yes, the architectures without IOMMU don't hit this problem.
>
> I meant that even if some architectures support IOMMUs, they set
> BIO_VMERGE_BOUNDARY to 0.
Keep in mind that these settings were added long before
we supported segment boundary restrictions.
Someone added code to handle segment boundaries, but didn't
fix any of the block I/O layer infrastructure :-)
Several platforms that have IOMMU but set these values to zero
actually did so for another reason. They considered being
required to always merge page-adjacent mappings virtually too
strong a requirement to meet %100 of the time.
next prev parent reply other threads:[~2008-07-11 19:42 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-07-10 21:56 Mikulas Patocka
2008-07-10 22:59 ` Julian Calaby
2008-07-10 23:57 ` Mikulas Patocka
2008-07-11 6:20 ` FUJITA Tomonori
2008-07-11 10:52 ` Mikulas Patocka
2008-07-11 11:15 ` FUJITA Tomonori
2008-07-11 19:41 ` David Miller [this message]
2008-07-11 20:22 ` Mikulas Patocka
2008-07-12 12:30 ` Andi Kleen
2008-07-13 13:34 ` Mikulas Patocka
2008-07-13 13:50 ` Andi Kleen
2008-07-13 19:46 ` David Miller
2008-07-13 20:13 ` Andi Kleen
2008-07-13 23:53 ` Mikulas Patocka
2008-07-14 0:48 ` David Miller
2008-07-14 12:16 ` Mikulas Patocka
2008-07-14 12:28 ` David Miller
2008-07-14 14:03 ` Mikulas Patocka
2008-07-14 21:37 ` David Miller
2008-07-14 23:16 ` Mikulas Patocka
2008-07-15 1:31 ` David Miller
2008-07-15 22:32 ` Mikulas Patocka
2008-07-15 22:37 ` David Miller
2008-07-15 22:59 ` Mikulas Patocka
2008-07-15 2:40 ` FUJITA Tomonori
2008-07-14 0:41 ` David Miller
2008-07-14 2:19 ` FUJITA Tomonori
2008-07-14 3:20 ` David Miller
2008-07-14 17:45 ` FUJITA Tomonori
2008-07-14 21:26 ` Mikulas Patocka
2008-07-15 2:40 ` FUJITA Tomonori
2008-07-15 12:09 ` Mikulas Patocka
2008-07-15 12:15 ` Andi Kleen
2008-07-15 13:16 ` Mikulas Patocka
2008-07-15 14:06 ` Andi Kleen
2008-07-15 12:19 ` FUJITA Tomonori
2008-07-16 3:10 ` David Miller
2008-07-16 4:38 ` FUJITA Tomonori
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