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Date: 25 Apr 2007 16:37:41 +0200 From: Andi Kleen <andi@...stfloor.org> To: Fengguang Wu <fengguang.wu@...il.com> Cc: Andrew Morton <akpm@...l.org>, Oleg Nesterov <oleg@...sign.ru>, Steven Pratt <slpratt@...tin.ibm.com>, Ram Pai <linuxram@...ibm.com>, linux-kernel@...r.kernel.org Subject: Re: [RFC][PATCH] on-demand readahead Fengguang Wu <fengguang.wu@...il.com> writes: > OVERHEADS > > The new code reduced the overheads of > > - excessively calling the readahead routine on small sized reads > (the current readahead code insists on seeing all requests) > > - doing a lot of pointless page-cache lookups for small cached files > (the current readahead only turns itself off after 256 cache hits, > unfortunately most files are < 1MB, so never see that chance) Would it make sense to keep track in the AS if the file is completely in cache? Then you could probably avoid a lot of these lookups for small in cache files > --- linux-2.6.21-rc7-mm1.orig/mm/readahead.c > +++ linux-2.6.21-rc7-mm1/mm/readahead.c > @@ -733,6 +733,11 @@ unsigned long max_sane_readahead(unsigne Quite simple patch, why is it that much simpler than your earlier patchkits? Or is that on top of them? You seem to have a lot of magic numbers. They probably all need symbols and explanations. Your white space also needs some work. -Andi - 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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