| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <deed9bb1-02b9-4e89-895b-38a84e5a9408@gmail.com>
Date: Thu, 23 Nov 2023 11:32:59 +0800
From: Qi Zheng <arch0.zheng@...il.com>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Qi Zheng <zhengqi.arch@...edance.com>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Dave Chinner <david@...morbit.com>
Subject: Re: [PATCH 2/7] mm: shrinker: Add a .to_text() method for shrinkers
Hi Kent,
On 2023/11/23 07:25, Kent Overstreet wrote:
> This adds a new callback method to shrinkers which they can use to
> describe anything relevant to memory reclaim about their internal state,
> for example object dirtyness.
I have no objection to this proposal, but maybe it would be better to
place this feature under CONFIG_SHRINKER_DEBUG?
Hi Roman, what do you think?
Also +CC Dave.
More comments below.
>
> This patch also adds shrinkers_to_text(), which reports on the top 10
> shrinkers - by object count - in sorted order, to be used in OOM
> reporting.
>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Qi Zheng <zhengqi.arch@...edance.com>
> Cc: Roman Gushchin <roman.gushchin@...ux.dev>
> Cc: linux-mm@...ck.org
> Signed-off-by: Kent Overstreet <kent.overstreet@...ux.dev>
> ---
> include/linux/shrinker.h | 6 +++-
> mm/shrinker.c | 73 +++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 77 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
> index 1a00be90d93a..968c55474e78 100644
> --- a/include/linux/shrinker.h
> +++ b/include/linux/shrinker.h
> @@ -24,6 +24,8 @@ struct shrinker_info {
> struct shrinker_info_unit *unit[];
> };
>
> +struct seq_buf;
> +
> /*
> * This struct is used to pass information from page reclaim to the shrinkers.
> * We consolidate the values for easier extension later.
> @@ -80,10 +82,12 @@ struct shrink_control {
> * @flags determine the shrinker abilities, like numa awareness
> */
> struct shrinker {
> + const char *name;
> unsigned long (*count_objects)(struct shrinker *,
> struct shrink_control *sc);
> unsigned long (*scan_objects)(struct shrinker *,
> struct shrink_control *sc);
> + void (*to_text)(struct seq_buf *, struct shrinker *);
The "to_text" looks a little strange, how about naming it
"stat_objects"?
>
> long batch; /* reclaim batch size, 0 = default */
> int seeks; /* seeks to recreate an obj */
> @@ -110,7 +114,6 @@ struct shrinker {
> #endif
> #ifdef CONFIG_SHRINKER_DEBUG
> int debugfs_id;
> - const char *name;
The name will only be allocated memory when the CONFIG_SHRINKER_DEBUG is
enabled, otherwise its value is NULL. So you can't move it out and use
it while CONFIG_SHRINKER_DEBUG is disabled.
> struct dentry *debugfs_entry;
> #endif
> /* objs pending delete, per node */
> @@ -135,6 +138,7 @@ __printf(2, 3)
> struct shrinker *shrinker_alloc(unsigned int flags, const char *fmt, ...);
> void shrinker_register(struct shrinker *shrinker);
> void shrinker_free(struct shrinker *shrinker);
> +void shrinkers_to_text(struct seq_buf *);
>
> static inline bool shrinker_try_get(struct shrinker *shrinker)
> {
> diff --git a/mm/shrinker.c b/mm/shrinker.c
> index dd91eab43ed3..4976dbac4c83 100644
> --- a/mm/shrinker.c
> +++ b/mm/shrinker.c
> @@ -1,8 +1,9 @@
> // SPDX-License-Identifier: GPL-2.0
> #include <linux/memcontrol.h>
> +#include <linux/rculist.h>
> #include <linux/rwsem.h>
> +#include <linux/seq_buf.h>
> #include <linux/shrinker.h>
> -#include <linux/rculist.h>
> #include <trace/events/vmscan.h>
>
> #include "internal.h"
> @@ -807,3 +808,73 @@ void shrinker_free(struct shrinker *shrinker)
> call_rcu(&shrinker->rcu, shrinker_free_rcu_cb);
> }
> EXPORT_SYMBOL_GPL(shrinker_free);
> +
> +void shrinker_to_text(struct seq_buf *out, struct shrinker *shrinker)
> +{
> + struct shrink_control sc = { .gfp_mask = GFP_KERNEL, };
> +
> + seq_buf_puts(out, shrinker->name);
> + seq_buf_printf(out, " objects: %lu\n", shrinker->count_objects(shrinker, &sc));
> +
> + if (shrinker->to_text) {
> + shrinker->to_text(out, shrinker);
> + seq_buf_puts(out, "\n");
> + }
> +}
> +
> +/**
> + * shrinkers_to_text - Report on shrinkers with highest usage
> + *
> + * This reports on the top 10 shrinkers, by object counts, in sorted order:
> + * intended to be used for OOM reporting.
> + */
> +void shrinkers_to_text(struct seq_buf *out)
> +{
> + struct shrinker *shrinker;
> + struct shrinker_by_mem {
> + struct shrinker *shrinker;
> + unsigned long mem;
The "mem" also looks a little strange, how about naming it
"freeable"?
> + } shrinkers_by_mem[10];
> + int i, nr = 0;
> +
> + if (!mutex_trylock(&shrinker_mutex)) {
> + seq_buf_puts(out, "(couldn't take shrinker lock)");
> + return;
> + }
We now have lockless method (RCU + refcount) to iterate shrinker_list,
please refer to shrink_slab().
Thanks,
Qi
> +
> + list_for_each_entry(shrinker, &shrinker_list, list) {
> + struct shrink_control sc = { .gfp_mask = GFP_KERNEL, };
> + unsigned long mem = shrinker->count_objects(shrinker, &sc);
> +
> + if (!mem || mem == SHRINK_STOP || mem == SHRINK_EMPTY)
> + continue;
> +
> + for (i = 0; i < nr; i++)
> + if (mem < shrinkers_by_mem[i].mem)
> + break;
> +
> + if (nr < ARRAY_SIZE(shrinkers_by_mem)) {
> + memmove(&shrinkers_by_mem[i + 1],
> + &shrinkers_by_mem[i],
> + sizeof(shrinkers_by_mem[0]) * (nr - i));
> + nr++;
> + } else if (i) {
> + i--;
> + memmove(&shrinkers_by_mem[0],
> + &shrinkers_by_mem[1],
> + sizeof(shrinkers_by_mem[0]) * i);
> + } else {
> + continue;
> + }
> +
> + shrinkers_by_mem[i] = (struct shrinker_by_mem) {
> + .shrinker = shrinker,
> + .mem = mem,
> + };
> + }
> +
> + for (i = nr - 1; i >= 0; --i)
> + shrinker_to_text(out, shrinkers_by_mem[i].shrinker);
> +
> + mutex_unlock(&shrinker_mutex);
> +}
Powered by blists - more mailing lists