From: Christophe JAILLET <christophe.jaillet@wanadoo.fr> To: Roman Gushchin <roman.gushchin@linux.dev>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org Cc: Dave Chinner <dchinner@redhat.com>, linux-kernel@vger.kernel.org, Yang Shi <shy828301@gmail.com>, Kent Overstreet <kent.overstreet@gmail.com>, Hillf Danton <hdanton@sina.com> Subject: Re: [PATCH v2 1/7] mm: introduce debugfs interface for kernel memory shrinkers Date: Sat, 23 Apr 2022 09:51:31 +0200 [thread overview] Message-ID: <0c64fd49-4ca3-1f5e-a69c-bb1d65f2263c@wanadoo.fr> (raw) In-Reply-To: <20220422202644.799732-2-roman.gushchin@linux.dev> 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 [...] > 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 [...] > +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); > + } [...]
WARNING: multiple messages have this Message-ID (diff)
From: Christophe JAILLET <christophe.jaillet@wanadoo.fr> To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org Subject: Re: [PATCH v2 1/7] mm: introduce debugfs interface for kernel memory shrinkers Date: Sat, 23 Apr 2022 09:51:31 +0200 [thread overview] Message-ID: <0c64fd49-4ca3-1f5e-a69c-bb1d65f2263c@wanadoo.fr> (raw) Message-ID: <20220423075131.wE1iSPYm0hwi9RttGpjkNFTSqCZpnhaq91uvS1qRmlQ@z> (raw) In-Reply-To: <20220422202644.799732-2-roman.gushchin@linux.dev> 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 [...] > 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 [...] > +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); > + } [...]
next prev parent reply other threads:[~2022-04-23 7:51 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-04-22 20:26 [PATCH v2 0/7] mm: introduce shrinker debugfs interface Roman Gushchin 2022-04-22 20:26 ` [PATCH v2 1/7] mm: introduce debugfs interface for kernel memory shrinkers Roman Gushchin 2022-04-23 7:51 ` Christophe JAILLET [this message] 2022-04-23 7:51 ` Christophe JAILLET 2022-04-22 20:26 ` [PATCH v2 2/7] mm: memcontrol: introduce mem_cgroup_ino() and mem_cgroup_get_from_ino() Roman Gushchin 2022-04-22 20:26 ` [PATCH v2 3/7] mm: introduce memcg interfaces for shrinker debugfs Roman Gushchin 2022-04-22 20:26 ` [PATCH v2 4/7] mm: introduce numa " Roman Gushchin 2022-04-22 20:26 ` [PATCH v2 5/7] mm: provide shrinkers with names Roman Gushchin 2022-04-23 7:46 ` Christophe JAILLET 2022-04-23 7:46 ` Christophe JAILLET 2022-04-28 0:25 ` Roman Gushchin 2022-04-22 20:26 ` [PATCH v2 6/7] docs: document shrinker debugfs Roman Gushchin 2022-04-22 20:26 ` [PATCH v2 7/7] tools: add memcg_shrinker.py Roman Gushchin [not found] ` <20220423003552.2914-1-hdanton@sina.com> 2022-04-23 1:29 ` [PATCH v2 3/7] mm: introduce memcg interfaces for shrinker debugfs Roman Gushchin 2022-04-26 6:02 ` [PATCH v2 0/7] mm: introduce shrinker debugfs interface Dave Chinner 2022-04-26 6:45 ` Kent Overstreet 2022-04-26 16:41 ` Roman Gushchin 2022-04-26 18:37 ` Kent Overstreet 2022-04-27 1:22 ` Dave Chinner 2022-04-27 2:18 ` Roman Gushchin 2022-04-26 19:05 ` Roman Gushchin 2022-04-27 1:02 ` Dave Chinner
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