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Date: Wed, 13 Apr 2011 04:37:36 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: Andrew Morton <akpm@...ux-foundation.org> Cc: Changli Gao <xiaosuo@...il.com>, Américo Wang <xiyou.wangcong@...il.com>, Jiri Slaby <jslaby@...e.cz>, azurIt <azurit@...ox.sk>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, Jiri Slaby <jirislaby@...il.com> Subject: Re: Regression from 2.6.36 Le mardi 12 avril 2011 à 18:31 -0700, Andrew Morton a écrit : > On Wed, 13 Apr 2011 09:23:11 +0800 Changli Gao <xiaosuo@...il.com> wrote: > > > On Wed, Apr 13, 2011 at 6:49 AM, Andrew Morton > > <akpm@...ux-foundation.org> wrote: > > > > > > It's somewhat unclear (to me) what caused this regression. > > > > > > Is it because the kernel is now doing large kmalloc()s for the fdtable, > > > and this makes the page allocator go nuts trying to satisfy high-order > > > page allocation requests? > > > > > > Is it because the kernel now will usually free the fdtable > > > synchronously within the rcu callback, rather than deferring this to a > > > workqueue? > > > > > > The latter seems unlikely, so I'm thinking this was a case of > > > high-order-allocations-considered-harmful? > > > > > > > Maybe, but I am not sure. Maybe my patch causes too many inner > > fragments. For example, when asking for 5 pages, get 8 pages, and 3 > > pages are wasted, then memory thrash happens finally. > > That theory sounds less likely, but could be tested by using > alloc_pages_exact(). > Very unlikely, since fdtable sizes are powers of two, unless you hit sysctl_nr_open and it was changed (default value being 2^20) -- 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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