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Message-ID: <20241021130027.3615969-1-ryan.roberts@arm.com>
Date: Mon, 21 Oct 2024 14:00:26 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Roman Gushchin <roman.gushchin@...ux.dev>,
Shakeel Butt <shakeel.butt@...ux.dev>,
Muchun Song <muchun.song@...ux.dev>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Ryan Roberts <ryan.roberts@....com>,
cgroups@...r.kernel.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Michal Hocko <mhocko@...e.com>
Subject: [PATCH v2] mm/memcontrol: Fix seq_buf size to save memory when PAGE_SIZE is large
Previously the seq_buf used for accumulating the memory.stat output was
sized at PAGE_SIZE. But the amount of output is invariant to PAGE_SIZE;
If 4K is enough on a 4K page system, then it should also be enough on a
64K page system, so we can save 60K on the static buffer used in
mem_cgroup_print_oom_meminfo(). Let's make it so.
This also has the beneficial side effect of removing a place in the code
that assumed PAGE_SIZE is a compile-time constant. So this helps our
quest towards supporting boot-time page size selection.
Signed-off-by: Ryan Roberts <ryan.roberts@....com>
Acked-by: Johannes Weiner <hannes@...xchg.org>
Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>
Acked-by: Michal Hocko <mhocko@...e.com>
Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>
---
mm/memcontrol.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 17af08367c68..5c3a8629ef3e 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -118,6 +118,7 @@ struct mem_cgroup *vmpressure_to_memcg(struct vmpressure *vmpr)
return container_of(vmpr, struct mem_cgroup, vmpressure);
}
+#define SEQ_BUF_SIZE SZ_4K
#define CURRENT_OBJCG_UPDATE_BIT 0
#define CURRENT_OBJCG_UPDATE_FLAG (1UL << CURRENT_OBJCG_UPDATE_BIT)
@@ -1527,7 +1528,7 @@ void mem_cgroup_print_oom_context(struct mem_cgroup *memcg, struct task_struct *
void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
{
/* Use static buffer, for the caller is holding oom_lock. */
- static char buf[PAGE_SIZE];
+ static char buf[SEQ_BUF_SIZE];
struct seq_buf s;
lockdep_assert_held(&oom_lock);
@@ -1553,7 +1554,7 @@ void mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg)
pr_info("Memory cgroup stats for ");
pr_cont_cgroup_path(memcg->css.cgroup);
pr_cont(":");
- seq_buf_init(&s, buf, sizeof(buf));
+ seq_buf_init(&s, buf, SEQ_BUF_SIZE);
memory_stat_format(memcg, &s);
seq_buf_do_printk(&s, KERN_INFO);
}
@@ -4194,12 +4195,12 @@ static int memory_events_local_show(struct seq_file *m, void *v)
int memory_stat_show(struct seq_file *m, void *v)
{
struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
- char *buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ char *buf = kmalloc(SEQ_BUF_SIZE, GFP_KERNEL);
struct seq_buf s;
if (!buf)
return -ENOMEM;
- seq_buf_init(&s, buf, PAGE_SIZE);
+ seq_buf_init(&s, buf, SEQ_BUF_SIZE);
memory_stat_format(memcg, &s);
seq_puts(m, buf);
kfree(buf);
--
2.43.0
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