Message-ID: <45BA3343.8070703@cfl.rr.com>
Date: Fri, 26 Jan 2007 11:58:43 -0500
From: Phillip Susi <psusi@cfl.rr.com>
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To: Mark Lord <lkml@rtr.ca>
CC: Denis Vlasenko <vda.linux@googlemail.com>,
       Michael Tokarev <mjt@tls.msk.ru>, Linus Torvalds <torvalds@osdl.org>,
       Viktor <vvp01@inbox.ru>, Aubrey <aubreylee@gmail.com>,
       Hua Zhong <hzhong@gmail.com>, Hugh Dickins <hugh@veritas.com>,
       linux-kernel@vger.kernel.org, hch@vger.kernel.org
Subject: Re: O_DIRECT question
References: <6d6a94c50701101857v2af1e097xde69e592135e54ae@mail.gmail.com> <45B90D19.60106@cfl.rr.com> <45B916F2.4070906@tls.msk.ru> <200701252211.39017.vda.linux@googlemail.com> <45BA2628.4030502@rtr.ca>
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Mark Lord wrote:
> You guys need to backup in this thread.
> 
> Every example of O_DIRECT here could be replaced with
> calls to mmap(), msync(), and madvise() (or posix_fadvise).
> 
> In addition to being at least as fast as O_DIRECT,
> these have the added benefit of using the page cache (avoiding reads for 
> data already present, handling multiple
> users of the same data, etc..).

Please actually _read_ the thread.  In every one of my posts I have 
shown why this is not the case.

To briefly rehash the core of the argument, there is no way to 
asynchronously manage IO with mmap, msync, madvise -- instead you take 
page faults or otherwise block, thus stalling the pipeline.

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