Messages in this thread |  | | Date | Sat, 23 Apr 2022 09:51:31 +0200 | Subject | Re: [PATCH v2 1/7] mm: introduce debugfs interface for kernel memory shrinkers | From | Christophe JAILLET <> |
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Le 22/04/2022 à 22:26, Roman Gushchin a écrit : > This commit introduces the /sys/kernel/debug/shrinker debugfs > interface which provides an ability to observe the state and interact > with individual kernel memory shrinkers. > > Because the feature is oriented on kernel developers and adds some > memory overhead (which shouldn't be large unless there is a huge > amount of registered shrinkers), it's guarded by a config option > (disabled by default). > > This commit introduces "count" and "scan" interfaces for each > shrinker registered in the system. > > Basic usage: > 1) Get the number of objects > $ cat count > > 2) Try to reclaim 500 objects > $ echo "500" > scan > > Following commits in the series will add memcg- and numa-specific > features. > > This commit gives debugfs entries simple numeric names, which are not > very convenient. The following commit in the series will provide > shrinkers with more meaningful names. > > Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev> > --- > include/linux/shrinker.h | 19 +++- > lib/Kconfig.debug | 9 ++ > mm/Makefile | 1 + > mm/shrinker_debug.c | 214 +++++++++++++++++++++++++++++++++++++++ > mm/vmscan.c | 6 +- > 5 files changed, 246 insertions(+), 3 deletions(-) > create mode 100644 mm/shrinker_debug.c
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> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c > new file mode 100644 > index 000000000000..4df7382a0737 > --- /dev/null > +++ b/mm/shrinker_debug.c
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> +int shrinker_debugfs_add(struct shrinker *shrinker) > +{ > + struct dentry *entry; > + char buf[256]; Later, this buffer is filled with a "%s-%d". (patch 5/7) The %s is generated out of a max 64 bytes long string.
To be consistent with the 2 buffers sizes, maybe this one could be reduced a bit to save some stack?
CJ
> + int id; > + > + lockdep_assert_held(&shrinker_rwsem); > + > + /* debugfs isn't initialized yet, add debugfs entries later. */ > + if (!shrinker_debugfs_root) > + return 0; > + > + id = ida_alloc(&shrinker_debugfs_ida, GFP_KERNEL); > + if (id < 0) > + return id; > + shrinker->debugfs_id = id; > + > + snprintf(buf, sizeof(buf), "%d", id); > + > + /* create debugfs entry */ > + entry = debugfs_create_dir(buf, shrinker_debugfs_root); > + if (IS_ERR(entry)) { > + ida_free(&shrinker_debugfs_ida, id); > + return PTR_ERR(entry); > + }
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