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Message-ID: <43EC92BE.7080409@yahoo.com.au>
Date: Sat, 11 Feb 2006 00:18:54 +1100
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: linux@horizon.com
CC: akpm@osdl.org, linux-kernel@vger.kernel.org, sct@redhat.com,
       torvalds@osdl.org
Subject: Re: msync() behaviour broken for MS_ASYNC, revert patch?
References: <20060210080013.6572.qmail@science.horizon.com>
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linux@horizon.com wrote:

>>That's what MS_ASYNC already does.
> 
> 
> Yes, in violation of the SuS spec.  That's what msync(0) already does,
> too, so the linux-specific extension already exists.
> 
> The standard description of MS_INVALIDATE is very confusing and poorly
> worded, but I think it's designed for a model where mmap() copies rather
> than playing page table tricks, and the OS has to copy the dirty pages
> back and forth between the buffer cache "by hand".  Looked at that way,
> the MS_INVALIDATE wording seems to be intended as something of a "commit
> memory writes back to the file system level" operation.
> 
> Which could also be expected to cause the traditional 30-second sync
> timeout to start applying to the written data.  In the current Linux

Yes as we already have something that does the pte->page work (I'd agree
with your interpretation of MS_INVALIDATE), then we definitely have room
to make MS_ASYNC more efficient for applications like yours that use it
properly.

-- 
SUSE Labs, Novell Inc.
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