The patch titled
Subject: mm/memcontrol: fix seq_buf size to save memory when PAGE_SIZE is large
has been added to the -mm mm-unstable branch. Its filename is
mm-memcontrol-fix-seq_buf-size-to-save-memory-when-page_size-is-large.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcontrol-fix-seq_buf-size-to-save-memory-when-page_size-is-large.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Ryan Roberts <ryan.roberts@xxxxxxx>
Subject: mm/memcontrol: fix seq_buf size to save memory when PAGE_SIZE is large
Date: Mon, 21 Oct 2024 14:00:26 +0100
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.
Link: https://lkml.kernel.org/r/20241021130027.3615969-1-ryan.roberts@xxxxxxx
Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Acked-by: Muchun Song <muchun.song@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/mm/memcontrol.c~mm-memcontrol-fix-seq_buf-size-to-save-memory-when-page_size-is-large
+++ a/mm/memcontrol.c
@@ -118,6 +118,7 @@ struct mem_cgroup *vmpressure_to_memcg(s
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
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
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(stru
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);
_
Patches currently in -mm which might be from ryan.roberts@xxxxxxx are
mm-memcontrol-fix-seq_buf-size-to-save-memory-when-page_size-is-large.patch
