From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH 1/2] super: fix calculation of shrinkable objects for small numbers Date: Thu, 20 Dec 2012 14:59:14 +0400 Message-ID: <50D2EF82.1050808@parallels.com> References: <1355906418-3603-1-git-send-email-glommer@parallels.com> <1355906418-3603-2-git-send-email-glommer@parallels.com> <20121220070657.GV15182@dastard> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20121220070657.GV15182@dastard> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Dave Chinner Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, Johannes Weiner , Michal Hocko , kamezawa.hiroyu@jp.fujitsu.com, Tejun Heo , Theodore Ts'o , Al Viro On 12/20/2012 11:06 AM, Dave Chinner wrote: > On Wed, Dec 19, 2012 at 12:40:17PM +0400, Glauber Costa wrote: >> The sysctl knob sysctl_vfs_cache_pressure is used to determine which >> percentage of the shrinkable objects in our cache we should actively try >> to shrink. >> >> It works great in situations in which we have many objects (at least >> more than 100), because the aproximation errors will be negligible. But >> if this is not the case, specially when total_objects < 100, we may end >> up concluding that we have no objects at all (total / 100 = 0, if total >> < 100). >> >> This is certainly not the biggest killer in the world, but may matter in >> very low kernel memory situations. >> >> Signed-off-by: Glauber Costa >> CC: Dave Chinner >> CC: "Theodore Ts'o" >> CC: Al Viro >> --- >> fs/super.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/super.c b/fs/super.c >> index 12f1237..660552c 100644 >> --- a/fs/super.c >> +++ b/fs/super.c >> @@ -104,7 +104,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc) >> sb->s_nr_inodes_unused + fs_objects; >> } >> >> - total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure; >> + total_objects = mult_frac(total_objects, sysctl_vfs_cache_pressure, 100); >> drop_super(sb); >> return total_objects; > > Hi Glauber, > > sysctl_vfs_cache_pressure all over the place with exactly the same > calculation. Can you fix all of them in one pass? > affirmative, sir!