On Fri, 22 Apr 2022 13:26:40 -0700 Roman Gushchin wrote:
> This commit introduces "count_memcg" and "scan_memcg" interfaces
> for memcg-aware shrinkers.
>
> Count_memcg using the following format:
> <cgroup inode number1> <count2>
> <cgroup inode number2> <count2>
> ...
>
> Memory cgroups with 0 associated objects are skipped.
>
> Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
> ---
> mm/shrinker_debug.c | 186 +++++++++++++++++++++++++++++++++-----------
> 1 file changed, 139 insertions(+), 47 deletions(-)
>
> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
> index 4df7382a0737..002d44d6ad56 100644
> --- a/mm/shrinker_debug.c
> +++ b/mm/shrinker_debug.c
> @@ -1,8 +1,10 @@
> // SPDX-License-Identifier: GPL-2.0
> #include <linux/idr.h>
> +#include <linux/slab.h>
> #include <linux/debugfs.h>
> #include <linux/seq_file.h>
> #include <linux/shrinker.h>
> +#include <linux/memcontrol.h>
>
> /* defined in vmscan.c */
> extern struct rw_semaphore shrinker_rwsem;
> @@ -11,25 +13,25 @@ extern struct list_head shrinker_list;
> static DEFINE_IDA(shrinker_debugfs_ida);
> static struct dentry *shrinker_debugfs_root;
>
> -static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
> +static unsigned long shrinker_count_objects(struct shrinker *shrinker,
> + struct mem_cgroup *memcg,
> + unsigned long *count_per_node)
> {
> - struct shrinker *shrinker = (struct shrinker *)m->private;
> unsigned long nr, total = 0;
> - int ret, nid;
> -
> - ret = down_read_killable(&shrinker_rwsem);
> - if (ret)
> - return ret;
> + int nid;
>
> for_each_node(nid) {
> struct shrink_control sc = {
> .gfp_mask = GFP_KERNEL,
> .nid = nid,
> + .memcg = memcg,
> };
>
> nr = shrinker->count_objects(shrinker, &sc);
> if (nr == SHRINK_EMPTY)
> nr = 0;
> + if (count_per_node)
> + count_per_node[nid] = nr;
> total += nr;
>
> if (!(shrinker->flags & SHRINKER_NUMA_AWARE))
> @@ -37,32 +39,17 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
>
> cond_resched();
Nit, add a line in response to signal before schedule, given the
killable above.
> }
> - up_read(&shrinker_rwsem);
> -
> - seq_printf(m, "%lu\n", total);
>
> - return ret;
> + return total;
> }
> -DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count);
>
> -static ssize_t shrinker_debugfs_scan_write(struct file *file,
> - const char __user *buf,
> - size_t size, loff_t *pos)
> +static int shrinker_scan_objects(struct shrinker *shrinker,
> + struct mem_cgroup *memcg,
> + unsigned long nr_to_scan)
> {
> - struct shrinker *shrinker = (struct shrinker *)file->private_data;
> - unsigned long nr, total = 0, nr_to_scan;
> - unsigned long *count_per_node = NULL;
> - int nid;
> - char kbuf[24];
> - 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 (kstrtoul(kbuf, 10, &nr_to_scan))
> - return -EINVAL;
> + unsigned long *count_per_node;
> + unsigned long total, nr;
> + int ret, nid;
>
> ret = down_read_killable(&shrinker_rwsem);
> if (ret)
> @@ -80,20 +67,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
> goto out;
> }
>
> - for_each_node(nid) {
> - struct shrink_control sc = {
> - .gfp_mask = GFP_KERNEL,
> - .nid = nid,
> - };
> -
> - nr = shrinker->count_objects(shrinker, &sc);
> - if (nr == SHRINK_EMPTY)
> - nr = 0;
> - count_per_node[nid] = nr;
> - total += nr;
> -
> - cond_resched();
> - }
> + total = shrinker_count_objects(shrinker, memcg, count_per_node);
> }
>
> for_each_node(nid) {
> @@ -102,13 +76,13 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
> .nid = nid,
> };
>
> - if (shrinker->flags & SHRINKER_NUMA_AWARE) {
> + if (count_per_node) {
> sc.nr_to_scan = nr_to_scan * count_per_node[nid] /
> (total ? total : 1);
> sc.nr_scanned = sc.nr_to_scan;
> } else {
> sc.nr_to_scan = nr_to_scan;
> - sc.nr_scanned = sc.nr_to_scan;
> + sc.nr_scanned = nr_to_scan;
> }
>
> nr = shrinker->scan_objects(shrinker, &sc);
> @@ -119,15 +93,51 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
> break;
>
> cond_resched();
> -
> }
> - ret = size;
> out:
> up_read(&shrinker_rwsem);
> kfree(count_per_node);
> return ret;
> }
>
> +static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
> +{
> + struct shrinker *shrinker = (struct shrinker *)m->private;
> + int ret;
> +
> + ret = down_read_killable(&shrinker_rwsem);
> + if (!ret) {
> + unsigned long total = shrinker_count_objects(shrinker, NULL, NULL);
> +
> + up_read(&shrinker_rwsem);
> + seq_printf(m, "%lu\n", total);
> + }
> + return ret;
> +}
> +DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count);
> +
> +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;
> + char kbuf[24];
> + 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 (kstrtoul(kbuf, 10, &nr_to_scan))
> + return -EINVAL;
> +
> + ret = shrinker_scan_objects(shrinker, NULL, nr_to_scan);
> +
> + return ret ? ret : size;
> +}
> +
> static int shrinker_debugfs_scan_open(struct inode *inode, struct file *file)
> {
> file->private_data = inode->i_private;
> @@ -140,6 +150,78 @@ static const struct file_operations shrinker_debugfs_scan_fops = {
> .write = shrinker_debugfs_scan_write,
> };
>
> +#ifdef CONFIG_MEMCG
> +static int shrinker_debugfs_count_memcg_show(struct seq_file *m, void *v)
> +{
> + struct shrinker *shrinker = (struct shrinker *)m->private;
> + struct mem_cgroup *memcg;
> + unsigned long total;
> + int ret;
> +
> + ret = down_read_killable(&shrinker_rwsem);
> + if (ret)
> + return ret;
> + rcu_read_lock();
A minute ... things like cond_resched() or mutex in individual shrinker
implementation can ruin your nice work within two seconds. The bigger
pain is can we rule them out from coming shrinkers?
Hillf
> +
> + memcg = mem_cgroup_iter(NULL, NULL, NULL);
> + do {
Nit, take a look at pending signal.
> + if (!mem_cgroup_online(memcg))
> + continue;
> +
> + total = shrinker_count_objects(shrinker, memcg, NULL);
> + if (!total)
> + continue;
> +
> + seq_printf(m, "%lu %lu\n", mem_cgroup_ino(memcg), total);
> + } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
> +
> + rcu_read_unlock();
> + up_read(&shrinker_rwsem);
> +
> + return 0;
> +}
> +DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count_memcg);
