From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pb0-f45.google.com (mail-pb0-f45.google.com [209.85.160.45]) by kanga.kvack.org (Postfix) with ESMTP id 5B6836B00DC for ; Wed, 6 Nov 2013 09:30:13 -0500 (EST) Received: by mail-pb0-f45.google.com with SMTP id ma3so9026566pbc.4 for ; Wed, 06 Nov 2013 06:30:12 -0800 (PST) Received: from psmtp.com ([74.125.245.172]) by mx.google.com with SMTP id pz2si17515271pac.202.2013.11.06.06.30.07 for ; Wed, 06 Nov 2013 06:30:09 -0800 (PST) Message-ID: <527A5269.7040900@parallels.com> Date: Wed, 6 Nov 2013 18:30:01 +0400 From: Maxim Patlasov MIME-Version: 1.0 Subject: Re: [PATCH] mm: add strictlimit knob References: <20131031142612.GA28003@kipc2.localdomain> <20131101142941.1161.40314.stgit@dhcp-10-30-17-2.sw.ru> <20131104140104.7936d263258a7a6753eb325e@linux-foundation.org> In-Reply-To: <20131104140104.7936d263258a7a6753eb325e@linux-foundation.org> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: karl.kiniger@med.ge.com, jack@suse.cz, linux-kernel@vger.kernel.org, t.artem@lycos.com, linux-mm@kvack.org, mgorman@suse.de, tytso@mit.edu, fengguang.wu@intel.com, torvalds@linux-foundation.org Hi Andrew, On 11/05/2013 02:01 AM, Andrew Morton wrote: > On Fri, 01 Nov 2013 18:31:40 +0400 Maxim Patlasov wrote: > >> "strictlimit" feature was introduced to enforce per-bdi dirty limits for >> FUSE which sets bdi max_ratio to 1% by default: >> >> http://www.http.com//article.gmane.org/gmane.linux.kernel.mm/105809 >> >> However the feature can be useful for other relatively slow or untrusted >> BDIs like USB flash drives and DVD+RW. The patch adds a knob to enable the >> feature: >> >> echo 1 > /sys/class/bdi/X:Y/strictlimit >> >> Being enabled, the feature enforces bdi max_ratio limit even if global (10%) >> dirty limit is not reached. Of course, the effect is not visible until >> max_ratio is decreased to some reasonable value. > I suggest replacing "max_ratio" here with the much more informative > "/sys/class/bdi/X:Y/max_ratio". > > Also, Documentation/ABI/testing/sysfs-class-bdi will need an update > please. OK, I'll update it, fix patch description and re-send the patch. > >> mm/backing-dev.c | 35 +++++++++++++++++++++++++++++++++++ >> 1 file changed, 35 insertions(+) >> > I'm not really sure what to make of the patch. I assume you tested it > and observed some effect. Could you please describe the test setup and > the effects in some detail? I plugged 16GB USB-flash in a node with 8GB RAM running 3.12.0-rc7 and started writing a huge file by "dd" (from /dev/zero to USB-flash mount-point). While writing I was observing "Dirty" counter as reported by /proc/meminfo. As expected it stabilized on a level about 1.2GB (15% of total RAM). Immediately after dd completed, the "umount" command took about 5 minutes. This corresponded to 5MB write throughput of the flash drive. Then I repeated the experiment after setting tunables: echo 1 > /sys/class/bdi/8\:16/max_ratio echo 1 > /sys/class/bdi/8\:16/strictlimit This time, "Dirty" counter became 100 times lesser - about 12MB and "umount" took about a second. Thanks, Maxim -- 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/ . Don't email: email@kvack.org