| Message ID | 20220509183820.573666-7-roman.gushchin@linux.dev (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: introduce shrinker debugfs interface | expand |
On Mon, May 09, 2022 at 11:38:20AM -0700, Roman Gushchin wrote: > Add a scan interface which allows to trigger scanning of a particular > shrinker and specify memcg and numa node. It's useful for testing, > debugging and profiling of a specific scan_objects() callback. > Unlike alternatives (creating a real memory pressure and dropping > caches via /proc/sys/vm/drop_caches) this interface allows to interact > with only one shrinker at once. Also, if a shrinker is misreporting > the number of objects (as some do), it doesn't affect scanning. > > Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev> > --- > .../admin-guide/mm/shrinker_debugfs.rst | 39 +++++++++- > mm/shrinker_debug.c | 73 +++++++++++++++++++ > 2 files changed, 108 insertions(+), 4 deletions(-) > > diff --git a/Documentation/admin-guide/mm/shrinker_debugfs.rst b/Documentation/admin-guide/mm/shrinker_debugfs.rst > index 6783f8190e63..8fecf81d60ee 100644 > --- a/Documentation/admin-guide/mm/shrinker_debugfs.rst > +++ b/Documentation/admin-guide/mm/shrinker_debugfs.rst > @@ -5,14 +5,16 @@ Shrinker Debugfs Interface > ========================== > > Shrinker debugfs interface provides a visibility into the kernel memory > -shrinkers subsystem and allows to get information about individual shrinkers. > +shrinkers subsystem and allows to get information about individual shrinkers > +and interact with them. > > For each shrinker registered in the system a directory in **<debugfs>/shrinker/** > is created. The directory's name is composed from the shrinker's name and an > unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. > > -Each shrinker directory contains the **count** file, which allows to trigger > -the *count_objects()* callback for each memcg and numa node (if applicable). > +Each shrinker directory contains **count** and **scan** files, which allow to > +trigger *count_objects()* and *scan_objects()* callbacks for each memcg and > +numa node (if applicable). > > Usage: > ------ > @@ -43,7 +45,7 @@ Usage: > > $ cd sb-btrfs\:vda2-24/ > $ ls > - count > + count scan > > 3. *Count objects* > > @@ -98,3 +100,32 @@ Usage: > 2877 84 0 > 293 1 0 > 735 8 0 > + > +4. *Scan objects* > + > + The expected input format:: > + > + <cgroup inode id> <numa id> <number of objects to scan> > + > + For a non-memcg-aware shrinker or on a system with no memory > + cgrups **0** should be passed as cgroup id. > + :: > + > + $ cd /sys/kernel/debug/shrinker/ > + $ cd sb-btrfs\:vda2-24/ > + > + $ cat count | head -n 5 > + 1 212 0 > + 21 97 0 > + 55 802 5 > + 2367 2 0 > + 225 13 0 > + > + $ echo "55 0 200" > scan > + > + $ cat count | head -n 5 > + 1 212 0 > + 21 96 0 > + 55 752 5 > + 2367 2 0 > + 225 13 0 > diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c > index 28b1c1ab60ef..8f67fef5a643 100644 > --- a/mm/shrinker_debug.c > +++ b/mm/shrinker_debug.c > @@ -101,6 +101,77 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) > } > DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count); > > +static int shrinker_debugfs_scan_open(struct inode *inode, struct file *file) > +{ > + file->private_data = inode->i_private; > + return nonseekable_open(inode, file); > +} > + > +static ssize_t shrinker_debugfs_scan_write(struct file *file, > + const char __user *buf, > + size_t size, loff_t *pos) > +{ > + struct shrinker *shrinker = (struct shrinker *)file->private_data; Seems we could drop the cast since ->private_data is void * type. > + unsigned long nr_to_scan = 0, ino; > + struct shrink_control sc = { > + .gfp_mask = GFP_KERNEL, > + }; > + struct mem_cgroup *memcg = NULL; > + int nid; > + char kbuf[72]; > + int read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1); > + ssize_t ret; > + > + if (copy_from_user(kbuf, buf, read_len)) > + return -EFAULT; > + kbuf[read_len] = '\0'; > + > + if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) < 2) > + return -EINVAL; > + > + if (nid < 0 || nid >= nr_node_ids) > + return -EINVAL; > + Should we break here if nr_to_scan is zero? > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) { > + memcg = mem_cgroup_get_from_ino(ino); > + if (!memcg || IS_ERR(memcg)) Should we drop the check of "!memcg" since mem_cgroup_get_from_ino cannot return NULL? > + return -ENOENT; > + > + if (!mem_cgroup_online(memcg)) { > + mem_cgroup_put(memcg); > + return -ENOENT; > + } > + } else { > + if (ino != 0) > + return -EINVAL; > + memcg = NULL; IIUC, memcg is already NULL if we reach here, right? Then the assignment is not necessary. Or we cound remove the initialization of 'memcg' where it is definned. > + } > + > + ret = down_read_killable(&shrinker_rwsem); > + if (ret) { > + mem_cgroup_put(memcg); > + return ret; > + } > + > + sc.nid = nid; > + sc.memcg = memcg; > + sc.nr_to_scan = nr_to_scan; > + sc.nr_scanned = nr_to_scan; > + > + shrinker->scan_objects(shrinker, &sc); > + > + up_read(&shrinker_rwsem); > + mem_cgroup_put(memcg); > + > + return ret ? ret : size; Seems "ret" is always equal to 0 here, should we simplify this to "return size"? Thanks. > +} > + > +static const struct file_operations shrinker_debugfs_scan_fops = { > + .owner = THIS_MODULE, > + .open = shrinker_debugfs_scan_open, > + .write = shrinker_debugfs_scan_write, > +}; > + > int shrinker_debugfs_add(struct shrinker *shrinker) > { > struct dentry *entry; > @@ -130,6 +201,8 @@ int shrinker_debugfs_add(struct shrinker *shrinker) > > debugfs_create_file("count", 0220, entry, shrinker, > &shrinker_debugfs_count_fops); > + debugfs_create_file("scan", 0440, entry, shrinker, > + &shrinker_debugfs_scan_fops); > return 0; > } > > -- > 2.35.3 > >
On Sun, May 22, 2022 at 07:35:59PM +0800, Muchun Song wrote: > On Mon, May 09, 2022 at 11:38:20AM -0700, Roman Gushchin wrote: > > Add a scan interface which allows to trigger scanning of a particular > > shrinker and specify memcg and numa node. It's useful for testing, > > debugging and profiling of a specific scan_objects() callback. > > Unlike alternatives (creating a real memory pressure and dropping > > caches via /proc/sys/vm/drop_caches) this interface allows to interact > > with only one shrinker at once. Also, if a shrinker is misreporting > > the number of objects (as some do), it doesn't affect scanning. > > > > Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev> > > --- > > .../admin-guide/mm/shrinker_debugfs.rst | 39 +++++++++- > > mm/shrinker_debug.c | 73 +++++++++++++++++++ > > 2 files changed, 108 insertions(+), 4 deletions(-) > > > > diff --git a/Documentation/admin-guide/mm/shrinker_debugfs.rst b/Documentation/admin-guide/mm/shrinker_debugfs.rst > > index 6783f8190e63..8fecf81d60ee 100644 > > --- a/Documentation/admin-guide/mm/shrinker_debugfs.rst > > +++ b/Documentation/admin-guide/mm/shrinker_debugfs.rst > > @@ -5,14 +5,16 @@ Shrinker Debugfs Interface > > ========================== > > > > Shrinker debugfs interface provides a visibility into the kernel memory > > -shrinkers subsystem and allows to get information about individual shrinkers. > > +shrinkers subsystem and allows to get information about individual shrinkers > > +and interact with them. > > > > For each shrinker registered in the system a directory in **<debugfs>/shrinker/** > > is created. The directory's name is composed from the shrinker's name and an > > unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. > > > > -Each shrinker directory contains the **count** file, which allows to trigger > > -the *count_objects()* callback for each memcg and numa node (if applicable). > > +Each shrinker directory contains **count** and **scan** files, which allow to > > +trigger *count_objects()* and *scan_objects()* callbacks for each memcg and > > +numa node (if applicable). > > > > Usage: > > ------ > > @@ -43,7 +45,7 @@ Usage: > > > > $ cd sb-btrfs\:vda2-24/ > > $ ls > > - count > > + count scan > > > > 3. *Count objects* > > > > @@ -98,3 +100,32 @@ Usage: > > 2877 84 0 > > 293 1 0 > > 735 8 0 > > + > > +4. *Scan objects* > > + > > + The expected input format:: > > + > > + <cgroup inode id> <numa id> <number of objects to scan> > > + > > + For a non-memcg-aware shrinker or on a system with no memory > > + cgrups **0** should be passed as cgroup id. > > + :: > > + > > + $ cd /sys/kernel/debug/shrinker/ > > + $ cd sb-btrfs\:vda2-24/ > > + > > + $ cat count | head -n 5 > > + 1 212 0 > > + 21 97 0 > > + 55 802 5 > > + 2367 2 0 > > + 225 13 0 > > + > > + $ echo "55 0 200" > scan > > + > > + $ cat count | head -n 5 > > + 1 212 0 > > + 21 96 0 > > + 55 752 5 > > + 2367 2 0 > > + 225 13 0 > > diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c > > index 28b1c1ab60ef..8f67fef5a643 100644 > > --- a/mm/shrinker_debug.c > > +++ b/mm/shrinker_debug.c > > @@ -101,6 +101,77 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) > > } > > DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count); > > > > +static int shrinker_debugfs_scan_open(struct inode *inode, struct file *file) > > +{ > > + file->private_data = inode->i_private; > > + return nonseekable_open(inode, file); > > +} > > + > > +static ssize_t shrinker_debugfs_scan_write(struct file *file, > > + const char __user *buf, > > + size_t size, loff_t *pos) > > +{ > > + struct shrinker *shrinker = (struct shrinker *)file->private_data; > > Seems we could drop the cast since ->private_data is void * type. Yep, fixed. Thanks! > > > + unsigned long nr_to_scan = 0, ino; > > + struct shrink_control sc = { > > + .gfp_mask = GFP_KERNEL, > > + }; > > + struct mem_cgroup *memcg = NULL; > > + int nid; > > + char kbuf[72]; > > + int read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1); > > + ssize_t ret; > > + > > + if (copy_from_user(kbuf, buf, read_len)) > > + return -EFAULT; > > + kbuf[read_len] = '\0'; > > + > > + if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) < 2) > > + return -EINVAL; > > + > > + if (nid < 0 || nid >= nr_node_ids) > > + return -EINVAL; > > + > > Should we break here if nr_to_scan is zero? Not a very likely scenario, but ok. > > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) { > > + memcg = mem_cgroup_get_from_ino(ino); > > + if (!memcg || IS_ERR(memcg)) > > Should we drop the check of "!memcg" since mem_cgroup_get_from_ino > cannot return NULL? It can if !CONFIG_MEMCG. You might argue that then shrinker can not have the SHRINKER_MEMCG_AWARE flag, but since it's not a hot path at all, I'll keep it for extra safety. > > > + return -ENOENT; > > + > > + if (!mem_cgroup_online(memcg)) { > > + mem_cgroup_put(memcg); > > + return -ENOENT; > > + } > > + } else { > > + if (ino != 0) > > + return -EINVAL; > > + memcg = NULL; > > IIUC, memcg is already NULL if we reach here, right? Then the > assignment is not necessary. Or we cound remove the initialization > of 'memcg' where it is definned. Right, removed. > > > + } > > + > > + ret = down_read_killable(&shrinker_rwsem); > > + if (ret) { > > + mem_cgroup_put(memcg); > > + return ret; > > + } > > + > > + sc.nid = nid; > > + sc.memcg = memcg; > > + sc.nr_to_scan = nr_to_scan; > > + sc.nr_scanned = nr_to_scan; > > + > > + shrinker->scan_objects(shrinker, &sc); > > + > > + up_read(&shrinker_rwsem); > > + mem_cgroup_put(memcg); > > + > > + return ret ? ret : size; > > Seems "ret" is always equal to 0 here, should we simplify this > to "return size"? Right. Thank you for the review!
On Mon, May 23, 2022 at 01:54:24PM -0700, Roman Gushchin wrote: > On Sun, May 22, 2022 at 07:35:59PM +0800, Muchun Song wrote: > > On Mon, May 09, 2022 at 11:38:20AM -0700, Roman Gushchin wrote: > > > Add a scan interface which allows to trigger scanning of a particular > > > shrinker and specify memcg and numa node. It's useful for testing, > > > debugging and profiling of a specific scan_objects() callback. > > > Unlike alternatives (creating a real memory pressure and dropping > > > caches via /proc/sys/vm/drop_caches) this interface allows to interact > > > with only one shrinker at once. Also, if a shrinker is misreporting > > > the number of objects (as some do), it doesn't affect scanning. > > > > > > Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev> > > > --- > > > .../admin-guide/mm/shrinker_debugfs.rst | 39 +++++++++- > > > mm/shrinker_debug.c | 73 +++++++++++++++++++ > > > 2 files changed, 108 insertions(+), 4 deletions(-) > > > > > > diff --git a/Documentation/admin-guide/mm/shrinker_debugfs.rst b/Documentation/admin-guide/mm/shrinker_debugfs.rst > > > index 6783f8190e63..8fecf81d60ee 100644 > > > --- a/Documentation/admin-guide/mm/shrinker_debugfs.rst > > > +++ b/Documentation/admin-guide/mm/shrinker_debugfs.rst > > > @@ -5,14 +5,16 @@ Shrinker Debugfs Interface > > > ========================== > > > > > > Shrinker debugfs interface provides a visibility into the kernel memory > > > -shrinkers subsystem and allows to get information about individual shrinkers. > > > +shrinkers subsystem and allows to get information about individual shrinkers > > > +and interact with them. > > > > > > For each shrinker registered in the system a directory in **<debugfs>/shrinker/** > > > is created. The directory's name is composed from the shrinker's name and an > > > unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. > > > > > > -Each shrinker directory contains the **count** file, which allows to trigger > > > -the *count_objects()* callback for each memcg and numa node (if applicable). > > > +Each shrinker directory contains **count** and **scan** files, which allow to > > > +trigger *count_objects()* and *scan_objects()* callbacks for each memcg and > > > +numa node (if applicable). > > > > > > Usage: > > > ------ > > > @@ -43,7 +45,7 @@ Usage: > > > > > > $ cd sb-btrfs\:vda2-24/ > > > $ ls > > > - count > > > + count scan > > > > > > 3. *Count objects* > > > > > > @@ -98,3 +100,32 @@ Usage: > > > 2877 84 0 > > > 293 1 0 > > > 735 8 0 > > > + > > > +4. *Scan objects* > > > + > > > + The expected input format:: > > > + > > > + <cgroup inode id> <numa id> <number of objects to scan> > > > + > > > + For a non-memcg-aware shrinker or on a system with no memory > > > + cgrups **0** should be passed as cgroup id. > > > + :: > > > + > > > + $ cd /sys/kernel/debug/shrinker/ > > > + $ cd sb-btrfs\:vda2-24/ > > > + > > > + $ cat count | head -n 5 > > > + 1 212 0 > > > + 21 97 0 > > > + 55 802 5 > > > + 2367 2 0 > > > + 225 13 0 > > > + > > > + $ echo "55 0 200" > scan > > > + > > > + $ cat count | head -n 5 > > > + 1 212 0 > > > + 21 96 0 > > > + 55 752 5 > > > + 2367 2 0 > > > + 225 13 0 > > > diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c > > > index 28b1c1ab60ef..8f67fef5a643 100644 > > > --- a/mm/shrinker_debug.c > > > +++ b/mm/shrinker_debug.c > > > @@ -101,6 +101,77 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) > > > } > > > DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count); > > > > > > +static int shrinker_debugfs_scan_open(struct inode *inode, struct file *file) > > > +{ > > > + file->private_data = inode->i_private; > > > + return nonseekable_open(inode, file); > > > +} > > > + > > > +static ssize_t shrinker_debugfs_scan_write(struct file *file, > > > + const char __user *buf, > > > + size_t size, loff_t *pos) > > > +{ > > > + struct shrinker *shrinker = (struct shrinker *)file->private_data; > > > > Seems we could drop the cast since ->private_data is void * type. > > Yep, fixed. Thanks! > > > > > > + unsigned long nr_to_scan = 0, ino; > > > + struct shrink_control sc = { > > > + .gfp_mask = GFP_KERNEL, > > > + }; > > > + struct mem_cgroup *memcg = NULL; > > > + int nid; > > > + char kbuf[72]; > > > + int read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1); > > > + ssize_t ret; > > > + > > > + if (copy_from_user(kbuf, buf, read_len)) > > > + return -EFAULT; > > > + kbuf[read_len] = '\0'; > > > + > > > + if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) < 2) > > > + return -EINVAL; > > > + > > > + if (nid < 0 || nid >= nr_node_ids) > > > + return -EINVAL; > > > + > > > > Should we break here if nr_to_scan is zero? > > Not a very likely scenario, but ok. > Agree. > > > > > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) { > > > + memcg = mem_cgroup_get_from_ino(ino); > > > + if (!memcg || IS_ERR(memcg)) > > > > Should we drop the check of "!memcg" since mem_cgroup_get_from_ino > > cannot return NULL? > > It can if !CONFIG_MEMCG. You might argue that then shrinker can not have > the SHRINKER_MEMCG_AWARE flag, but since it's not a hot path at all, > I'll keep it for extra safety. > Make sense. > > > > > + return -ENOENT; > > > + > > > + if (!mem_cgroup_online(memcg)) { > > > + mem_cgroup_put(memcg); > > > + return -ENOENT; > > > + } > > > + } else { > > > + if (ino != 0) > > > + return -EINVAL; > > > + memcg = NULL; > > > > IIUC, memcg is already NULL if we reach here, right? Then the > > assignment is not necessary. Or we cound remove the initialization > > of 'memcg' where it is definned. > > Right, removed. > > > > > > + } > > > + > > > + ret = down_read_killable(&shrinker_rwsem); > > > + if (ret) { > > > + mem_cgroup_put(memcg); > > > + return ret; > > > + } > > > + > > > + sc.nid = nid; > > > + sc.memcg = memcg; > > > + sc.nr_to_scan = nr_to_scan; > > > + sc.nr_scanned = nr_to_scan; > > > + > > > + shrinker->scan_objects(shrinker, &sc); > > > + > > > + up_read(&shrinker_rwsem); > > > + mem_cgroup_put(memcg); > > > + > > > + return ret ? ret : size; > > > > Seems "ret" is always equal to 0 here, should we simplify this > > to "return size"? > > Right. > > Thank you for the review! > My pleasure. Thanks.
diff --git a/Documentation/admin-guide/mm/shrinker_debugfs.rst b/Documentation/admin-guide/mm/shrinker_debugfs.rst index 6783f8190e63..8fecf81d60ee 100644 --- a/Documentation/admin-guide/mm/shrinker_debugfs.rst +++ b/Documentation/admin-guide/mm/shrinker_debugfs.rst @@ -5,14 +5,16 @@ Shrinker Debugfs Interface ========================== Shrinker debugfs interface provides a visibility into the kernel memory -shrinkers subsystem and allows to get information about individual shrinkers. +shrinkers subsystem and allows to get information about individual shrinkers +and interact with them. For each shrinker registered in the system a directory in **<debugfs>/shrinker/** is created. The directory's name is composed from the shrinker's name and an unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. -Each shrinker directory contains the **count** file, which allows to trigger -the *count_objects()* callback for each memcg and numa node (if applicable). +Each shrinker directory contains **count** and **scan** files, which allow to +trigger *count_objects()* and *scan_objects()* callbacks for each memcg and +numa node (if applicable). Usage: ------ @@ -43,7 +45,7 @@ Usage: $ cd sb-btrfs\:vda2-24/ $ ls - count + count scan 3. *Count objects* @@ -98,3 +100,32 @@ Usage: 2877 84 0 293 1 0 735 8 0 + +4. *Scan objects* + + The expected input format:: + + <cgroup inode id> <numa id> <number of objects to scan> + + For a non-memcg-aware shrinker or on a system with no memory + cgrups **0** should be passed as cgroup id. + :: + + $ cd /sys/kernel/debug/shrinker/ + $ cd sb-btrfs\:vda2-24/ + + $ cat count | head -n 5 + 1 212 0 + 21 97 0 + 55 802 5 + 2367 2 0 + 225 13 0 + + $ echo "55 0 200" > scan + + $ cat count | head -n 5 + 1 212 0 + 21 96 0 + 55 752 5 + 2367 2 0 + 225 13 0 diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c index 28b1c1ab60ef..8f67fef5a643 100644 --- a/mm/shrinker_debug.c +++ b/mm/shrinker_debug.c @@ -101,6 +101,77 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) } DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count); +static int shrinker_debugfs_scan_open(struct inode *inode, struct file *file) +{ + file->private_data = inode->i_private; + return nonseekable_open(inode, file); +} + +static ssize_t shrinker_debugfs_scan_write(struct file *file, + const char __user *buf, + size_t size, loff_t *pos) +{ + struct shrinker *shrinker = (struct shrinker *)file->private_data; + unsigned long nr_to_scan = 0, ino; + struct shrink_control sc = { + .gfp_mask = GFP_KERNEL, + }; + struct mem_cgroup *memcg = NULL; + int nid; + char kbuf[72]; + int read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1); + ssize_t ret; + + if (copy_from_user(kbuf, buf, read_len)) + return -EFAULT; + kbuf[read_len] = '\0'; + + if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) < 2) + return -EINVAL; + + if (nid < 0 || nid >= nr_node_ids) + return -EINVAL; + + if (shrinker->flags & SHRINKER_MEMCG_AWARE) { + memcg = mem_cgroup_get_from_ino(ino); + if (!memcg || IS_ERR(memcg)) + return -ENOENT; + + if (!mem_cgroup_online(memcg)) { + mem_cgroup_put(memcg); + return -ENOENT; + } + } else { + if (ino != 0) + return -EINVAL; + memcg = NULL; + } + + ret = down_read_killable(&shrinker_rwsem); + if (ret) { + mem_cgroup_put(memcg); + return ret; + } + + sc.nid = nid; + sc.memcg = memcg; + sc.nr_to_scan = nr_to_scan; + sc.nr_scanned = nr_to_scan; + + shrinker->scan_objects(shrinker, &sc); + + up_read(&shrinker_rwsem); + mem_cgroup_put(memcg); + + return ret ? ret : size; +} + +static const struct file_operations shrinker_debugfs_scan_fops = { + .owner = THIS_MODULE, + .open = shrinker_debugfs_scan_open, + .write = shrinker_debugfs_scan_write, +}; + int shrinker_debugfs_add(struct shrinker *shrinker) { struct dentry *entry; @@ -130,6 +201,8 @@ int shrinker_debugfs_add(struct shrinker *shrinker) debugfs_create_file("count", 0220, entry, shrinker, &shrinker_debugfs_count_fops); + debugfs_create_file("scan", 0440, entry, shrinker, + &shrinker_debugfs_scan_fops); return 0; }
Add a scan interface which allows to trigger scanning of a particular shrinker and specify memcg and numa node. It's useful for testing, debugging and profiling of a specific scan_objects() callback. Unlike alternatives (creating a real memory pressure and dropping caches via /proc/sys/vm/drop_caches) this interface allows to interact with only one shrinker at once. Also, if a shrinker is misreporting the number of objects (as some do), it doesn't affect scanning. Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev> --- .../admin-guide/mm/shrinker_debugfs.rst | 39 +++++++++- mm/shrinker_debug.c | 73 +++++++++++++++++++ 2 files changed, 108 insertions(+), 4 deletions(-)