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Message-ID: <20101102012006.GA3432@localhost> Date: Tue, 2 Nov 2010 09:20:06 +0800 From: Wu Fengguang <fengguang.wu@...el.com> To: Dimitrios Apostolou <jimis@....net> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: 2.6.36 io bring the system to its knees On Mon, Nov 01, 2010 at 01:09:34AM +0000, Dimitrios Apostolou wrote: > Hello, > > On Sun, 31 Oct 2010 09:51:32 +0800, Wu Fengguang wrote: > > It may also help to lower the dirty ratio. > > > > echo 5 > /proc/sys/vm/dirty_ratio > > > > Memory pressure + heavy write can easily hurt responsiveness. > > > > - eats up to 20% (the default value for dirty_ratio) memory with dirty > > pages and hence increase the memory pressure and number of swap IO > > My experience has been different with that. Wouldn't it make more sense > to _increase_ dirty_ratio (to 50 lets say) and at the same time decrease > dirty_background_ratio? That way writing to disk starts early, but the > related apps stall waiting for I/O only when dirty_ratio is reached. 50% dirty ratio may help before the system goes thrashing (writing processes will be throttled less/later). However Aidar is seeing hours of unresponsiveness with heavy IO, in this case large dirty ratio won't help reduce the throttling any more. Thanks, Fengguang -- 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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