linux-kernel - Re: [PATCH v3 3/6] mm: shrinkers: provide shrinkers with names

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Date:   Mon, 23 May 2022 19:18:22 -0700
From:   Roman Gushchin <roman.gushchin@...ux.dev>
To:     Dave Chinner <dchinner@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Kent Overstreet <kent.overstreet@...il.com>,
        Hillf Danton <hdanton@...a.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
Subject: Re: [PATCH v3 3/6] mm: shrinkers: provide shrinkers with names

On Mon, May 23, 2022 at 08:13:41AM +1000, Dave Chinner wrote:
> On Mon, May 09, 2022 at 11:38:17AM -0700, Roman Gushchin wrote:
> > Currently shrinkers are anonymous objects. For debugging purposes they
> > can be identified by count/scan function names, but it's not always
> > useful: e.g. for superblock's shrinkers it's nice to have at least
> > an idea of to which superblock the shrinker belongs.
> > 
> > This commit adds names to shrinkers. register_shrinker() and
> > prealloc_shrinker() functions are extended to take a format and
> > arguments to master a name.
> > 
> > In some cases it's not possible to determine a good name at the time
> > when a shrinker is allocated. For such cases shrinker_debugfs_rename()
> > is provided.
> > 
> > After this change the shrinker debugfs directory looks like:
> >   $ cd /sys/kernel/debug/shrinker/
> >   $ ls
> >     dqcache-16          sb-hugetlbfs-17  sb-rootfs-2      sb-tmpfs-50
> >     kfree_rcu-0         sb-hugetlbfs-33  sb-securityfs-6  sb-tracefs-13
> >     sb-aio-20           sb-iomem-12      sb-selinuxfs-22  sb-xfs:vda1-36
> >     sb-anon_inodefs-15  sb-mqueue-21     sb-sockfs-8      sb-zsmalloc-19
> >     sb-bdev-3           sb-nsfs-4        sb-sysfs-26      shadow-18
> >     sb-bpf-32           sb-pipefs-14     sb-tmpfs-1       thp_deferred_split-10
> >     sb-btrfs:vda2-24    sb-proc-25       sb-tmpfs-27      thp_zero-9
> >     sb-cgroup2-30       sb-proc-39       sb-tmpfs-29      xfs_buf-37
> >     sb-configfs-23      sb-proc-41       sb-tmpfs-35      xfs_inodegc-38
>                                                             ^^^^^^^^^^^^^^
> 
> These XFS shrinkers are also per-block device like the superblock.
> They need to read like "sb-xfs:vda1-36". and even though it is not
> in this list, the xfs dquot shrinker will need this as well.

Sure, will do in v4. Thanks!

> 
> 
> >     sb-dax-11           sb-proc-45       sb-tmpfs-40      zspool-34
> >     sb-debugfs-7        sb-proc-46       sb-tmpfs-42
> >     sb-devpts-28        sb-proc-47       sb-tmpfs-43
> >     sb-devtmpfs-5       sb-pstore-31     sb-tmpfs-44
> 
> The proc and tmpfs shrinkers have the same problem - what instance
> do they actually refer to?

Any ideas on how to name/identify them?