Message-ID: <45BE161A.2000504@cfl.rr.com>
Date: Mon, 29 Jan 2007 10:43:22 -0500
From: Phillip Susi <psusi@cfl.rr.com>
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To: Denis Vlasenko <vda.linux@googlemail.com>
CC: Bill Davidsen <davidsen@tmr.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@infradead.org
Subject: Re: O_DIRECT question
References: <6d6a94c50701101857v2af1e097xde69e592135e54ae@mail.gmail.com> <200701270035.31285.vda.linux@googlemail.com> <45BCBECE.4080405@tmr.com> <200701281803.08201.vda.linux@googlemail.com>
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Denis Vlasenko wrote:
> I still don't see much difference between O_SYNC and O_DIRECT write
> semantic.

Yes, if you change the normal io paths to properly support playing 
vmsplice games ( which have a number of corner cases ) to get the zero 
copy, and support madvise() and O_SYNC to control caching behavior, and 
fix all the error handling corner cases, then you may be able to do away 
with O_DIRECT.

I believe that doing all that will be much more complex than O_DIRECT 
however.

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