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Date: Fri, 26 Aug 2011 08:18:01 +0200 From: Stefan Priebe - Profihost AG <s.priebe@...fihost.ag> To: Zhu Yanhai <zhu.yanhai@...il.com> CC: Wu Fengguang <fengguang.wu@...el.com>, Pekka Enberg <penberg@...nel.org>, LKML <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>, Mel Gorman <mel@....ul.ie>, Jens Axboe <jaxboe@...ionio.com>, Linux Netdev List <netdev@...r.kernel.org> Subject: Re: slow performance on disk/network i/o full speed after drop_caches Yanhai, > Stefan, is your zone_reclaim_mode enabled? try 'cat > /proc/sys/vm/zone_reclaim_mode', > and echo 0 to it to disable. you're abssolutely corect zone_reclaim_mode is on - but why? There must be some linux software which switches it on. ~# grep 'zone_reclaim_mode' /etc/sysctl.* -r -i ~# also ~# grep 'zone_reclaim_mode' /etc/sysctl.* -r -i ~# tells us nothing. I've then read this: "zone_reclaim_mode is set during bootup to 1 if it is determined that pages from remote zones will cause a measurable performance reduction. The page allocator will then reclaim easily reusable pages (those page cache pages that are currently not used) before allocating off node pages." Why does the kernel do that here in our case on these machines. Stefan -- 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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