From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [PATCH 1/2] super: fix calculation of shrinkable objects for small numbers Date: Thu, 20 Dec 2012 18:06:57 +1100 Message-ID: <20121220070657.GV15182@dastard> References: <1355906418-3603-1-git-send-email-glommer@parallels.com> <1355906418-3603-2-git-send-email-glommer@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Johannes Weiner , Michal Hocko , kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org, Tejun Heo , Theodore Ts'o , Al Viro To: Glauber Costa Return-path: Content-Disposition: inline In-Reply-To: <1355906418-3603-2-git-send-email-glommer-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-fsdevel.vger.kernel.org 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? Cheers, Dave. -- Dave Chinner david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org