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In message <Pine.LNX.4.44.0205100854370.2230-100000@home.transmeta.com>, > : Li nus Torvalds writes: > > On Fri, 10 May 2002, Lincoln Dale wrote: > > > > so O_DIRECT in 2.4.18 still shows up as a 55% performance hit versus no > > O_DIRECT. anyone have any clues? > > Yes. > > O_DIRECT isn't doing any read-ahead. > > For O_DIRECT to be a win, you need to make it asynchronous. > > Linus O_DIRECT is especially useful for applications which maintain their own cache, e.g. a database. And adding Async to it is an even bigger bonus (another Oracleism we did in PTX). No read ahead, no attempt to keep the buffer in memory until memory pressure kicks in. Just a good tool for doing random IO (like an OLTP database would do). gerrit - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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