From: Dave Chinner <david@fromorbit.com>
To: Glauber Costa <glommer@parallels.com>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
cgroups@vger.kernel.org, Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@suse.cz>,
kamezawa.hiroyu@jp.fujitsu.com, Tejun Heo <tj@kernel.org>,
Theodore Ts'o <tytso@mit.edu>, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH 1/2] super: fix calculation of shrinkable objects for small numbers
Date: Thu, 20 Dec 2012 18:06:57 +1100 [thread overview]
Message-ID: <20121220070657.GV15182@dastard> (raw)
In-Reply-To: <1355906418-3603-2-git-send-email-glommer@parallels.com>
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 <glommer@parallels.com>
> CC: Dave Chinner <david@fromorbit.com>
> CC: "Theodore Ts'o" <tytso@mit.edu>
> CC: Al Viro <viro@zeniv.linux.org.uk>
> ---
> 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@fromorbit.com
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next prev parent reply other threads:[~2012-12-20 7:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-19 8:40 [PATCH 0/2] slightly change shrinker behaviour for very small object sets Glauber Costa
2012-12-19 8:40 ` [PATCH 1/2] super: fix calculation of shrinkable objects for small numbers Glauber Costa
2012-12-20 7:06 ` Dave Chinner [this message]
2012-12-20 10:59 ` Glauber Costa
2012-12-19 8:40 ` [PATCH 2/2] vmscan: take at least one pass with shrinkers Glauber Costa
2012-12-20 7:08 ` Dave Chinner
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