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Date: Fri, 26 Jan 2007 13:23:28 -0500 From: Bill Davidsen <davidsen@....com> To: Denis Vlasenko <vda.linux@...glemail.com> CC: Michael Tokarev <mjt@....msk.ru>, Phillip Susi <psusi@....rr.com>, Linus Torvalds <torvalds@...l.org>, Viktor <vvp01@...ox.ru>, Aubrey <aubreylee@...il.com>, Hua Zhong <hzhong@...il.com>, Hugh Dickins <hugh@...itas.com>, linux-kernel@...r.kernel.org, hch@...radead.org, kenneth.w.chen@in Subject: Re: O_DIRECT question Denis Vlasenko wrote: > On Thursday 25 January 2007 21:45, Michael Tokarev wrote: >> Phillip Susi wrote: >>> Denis Vlasenko wrote: >>>> You mean "You can use aio_write" ? >>> Exactly. You generally don't use O_DIRECT without aio. Combining the >>> two is what gives the big win. >> Well, it's not only aio. Multithreaded I/O also helps alot -- all this, >> say, to utilize a raid array with many spindles. >> >> But even single-threaded I/O but in large quantities benefits from O_DIRECT >> significantly, and I pointed this out before. > > Which shouldn't be true. There is no fundamental reason why > ordinary writes should be slower than O_DIRECT. > Other than the copy to buffer taking CPU and memory resources. -- Bill Davidsen <davidsen@....com> "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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