From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755798Ab1DMChq (ORCPT ); Tue, 12 Apr 2011 22:37:46 -0400 Received: from mail-wy0-f174.google.com ([74.125.82.174]:55910 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753247Ab1DMCho (ORCPT ); Tue, 12 Apr 2011 22:37:44 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:to:cc:in-reply-to:references:content-type:date :message-id:mime-version:x-mailer:content-transfer-encoding; b=jKQObL4NnpUPo6rPJU/Ds7yr3B8ABypt7nqH5QSUbsCNBD4GMU+ph69fGZw1RF+Tyi F6Z/Y1N+mjkrlaD4WCaixicGVoCBhs8Mse3pSnP106UkeGrlYdrn6DePNfnNbeNPZYdm pKfACI8vslCCllwhRHHLoX/RLxTnR8kiQJGW8= Subject: Re: Regression from 2.6.36 From: Eric Dumazet To: Andrew Morton Cc: Changli Gao , =?ISO-8859-1?Q?Am=E9rico?= Wang , Jiri Slaby , azurIt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Jiri Slaby In-Reply-To: <20110412183132.a854bffc.akpm@linux-foundation.org> References: <20110315132527.130FB80018F1@mail1005.cent> <20110317001519.GB18911@kroah.com> <20110407120112.E08DCA03@pobox.sk> <4D9D8FAA.9080405@suse.cz> <1302177428.3357.25.camel@edumazet-laptop> <1302178426.3357.34.camel@edumazet-laptop> <1302190586.3357.45.camel@edumazet-laptop> <20110412154906.70829d60.akpm@linux-foundation.org> <20110412183132.a854bffc.akpm@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Date: Wed, 13 Apr 2011 04:37:36 +0200 Message-ID: <1302662256.2811.27.camel@edumazet-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le mardi 12 avril 2011 à 18:31 -0700, Andrew Morton a écrit : > On Wed, 13 Apr 2011 09:23:11 +0800 Changli Gao wrote: > > > On Wed, Apr 13, 2011 at 6:49 AM, Andrew Morton > > 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) From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: Regression from 2.6.36 Date: Wed, 13 Apr 2011 04:37:36 +0200 Message-ID: <1302662256.2811.27.camel@edumazet-laptop> References: <20110315132527.130FB80018F1@mail1005.cent> <20110317001519.GB18911@kroah.com> <20110407120112.E08DCA03@pobox.sk> <4D9D8FAA.9080405@suse.cz> <1302177428.3357.25.camel@edumazet-laptop> <1302178426.3357.34.camel@edumazet-laptop> <1302190586.3357.45.camel@edumazet-laptop> <20110412154906.70829d60.akpm@linux-foundation.org> <20110412183132.a854bffc.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Cc: Changli Gao , =?ISO-8859-1?Q?Am=E9rico?= Wang , Jiri Slaby , azurIt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Jiri Slaby To: Andrew Morton Return-path: In-Reply-To: <20110412183132.a854bffc.akpm@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org Le mardi 12 avril 2011 =C3=A0 18:31 -0700, Andrew Morton a =C3=A9crit : > On Wed, 13 Apr 2011 09:23:11 +0800 Changli Gao wrot= e: >=20 > > On Wed, Apr 13, 2011 at 6:49 AM, Andrew Morton > > wrote: > > > > > > It's somewhat unclear (to me) what caused this regression. > > > > > > Is it because the kernel is now doing large kmalloc()s for the fdta= ble, > > > and this makes the page allocator go nuts trying to satisfy high-or= der > > > page allocation requests? > > > > > > Is it because the kernel now will usually free the fdtable > > > synchronously within the rcu callback, rather than deferring this t= o a > > > workqueue? > > > > > > The latter seems unlikely, so I'm thinking this was a case of > > > high-order-allocations-considered-harmful? > > > > >=20 > > 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. >=20 > That theory sounds less likely, but could be tested by using > alloc_pages_exact(). >=20 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter= .ca/ Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 726B8900086 for ; Tue, 12 Apr 2011 22:37:45 -0400 (EDT) Received: by wyf19 with SMTP id 19so183864wyf.14 for ; Tue, 12 Apr 2011 19:37:43 -0700 (PDT) Subject: Re: Regression from 2.6.36 From: Eric Dumazet In-Reply-To: <20110412183132.a854bffc.akpm@linux-foundation.org> References: <20110315132527.130FB80018F1@mail1005.cent> <20110317001519.GB18911@kroah.com> <20110407120112.E08DCA03@pobox.sk> <4D9D8FAA.9080405@suse.cz> <1302177428.3357.25.camel@edumazet-laptop> <1302178426.3357.34.camel@edumazet-laptop> <1302190586.3357.45.camel@edumazet-laptop> <20110412154906.70829d60.akpm@linux-foundation.org> <20110412183132.a854bffc.akpm@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" Date: Wed, 13 Apr 2011 04:37:36 +0200 Message-ID: <1302662256.2811.27.camel@edumazet-laptop> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Changli Gao , =?ISO-8859-1?Q?Am=E9rico?= Wang , Jiri Slaby , azurIt , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Jiri Slaby Le mardi 12 avril 2011 A 18:31 -0700, Andrew Morton a A(C)crit : > On Wed, 13 Apr 2011 09:23:11 +0800 Changli Gao wrote: > > > On Wed, Apr 13, 2011 at 6:49 AM, Andrew Morton > > 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org