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charset=us-ascii Content-Disposition: inline In-Reply-To: <20230426133919.1342942-2-yosryahmed@google.com> X-Stat-Signature: 5mht3bbj1jf73fertnsk3z1c9zhwsr7y X-Rspam-User: X-Rspamd-Queue-Id: C9F78180020 X-Rspamd-Server: rspam06 X-HE-Tag: 1682522654-243058 X-HE-Meta: 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 yQKJOvIz JhpK0ztVLgPrJ1sx0PwwNuEpG0/dU4eOPiSEEn3b46FD8jgBN8Nwfsesxn4XWaaKKayzJXXxtw6haHDQNmVL02KYEPA+BUnEMjo2AX6s6rUAZG0gCu3+GuPvwT/5PgZ7gRCsDUw94ToSsJDbzv41/wmvrKFG8ru1o1OUHVENZeceOf++irw8hqAgVb7UTCHlszWkUTEVOgmpaxECwtA6rdYQKLtllxxpQ6nbiOcdiIVfXxEU+/M5s54zZcVnKTsrA+Xrr0s6tIl6qspQD/KyzSe45FA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 26-04-23 13:39:18, Yosry Ahmed wrote: > Currently, we format all the memcg stats into a buffer in > mem_cgroup_print_oom_meminfo() and use pr_info() to dump it to the logs. > However, this buffer is large in size. Although it is currently working > as intended, ther is a dependency between the memcg stats buffer and the > printk record size limit. > > If we add more stats in the future and the buffer becomes larger than > the printk record size limit, or if the prink record size limit is > reduced, the logs may be truncated. > > It is safer to use seq_buf_do_printk(), which will automatically break > up the buffer at line breaks and issue small printk() calls. > > Refactor the code to move the seq_buf from memory_stat_format() to its > callers, and use seq_buf_do_printk() to print the seq_buf in > mem_cgroup_print_oom_meminfo(). > > Signed-off-by: Yosry Ahmed No objection from me but is it possible that more printk calls (one per line with this change correct?) would add a contention on the printk path? Acked-by: Michal Hocko > --- > mm/memcontrol.c | 27 ++++++++++++++------------- > 1 file changed, 14 insertions(+), 13 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 5abffe6f8389..5922940f92c9 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1551,13 +1551,10 @@ static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg, > return memcg_page_state(memcg, item) * memcg_page_state_unit(item); > } > > -static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize) > +static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s) > { > - struct seq_buf s; > int i; > > - seq_buf_init(&s, buf, bufsize); > - > /* > * Provide statistics on the state of the memory subsystem as > * well as cumulative event counters that show past behavior. > @@ -1574,21 +1571,21 @@ static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize) > u64 size; > > size = memcg_page_state_output(memcg, memory_stats[i].idx); > - seq_buf_printf(&s, "%s %llu\n", memory_stats[i].name, size); > + seq_buf_printf(s, "%s %llu\n", memory_stats[i].name, size); > > if (unlikely(memory_stats[i].idx == NR_SLAB_UNRECLAIMABLE_B)) { > size += memcg_page_state_output(memcg, > NR_SLAB_RECLAIMABLE_B); > - seq_buf_printf(&s, "slab %llu\n", size); > + seq_buf_printf(s, "slab %llu\n", size); > } > } > > /* Accumulated memory events */ > - seq_buf_printf(&s, "pgscan %lu\n", > + seq_buf_printf(s, "pgscan %lu\n", > memcg_events(memcg, PGSCAN_KSWAPD) + > memcg_events(memcg, PGSCAN_DIRECT) + > memcg_events(memcg, PGSCAN_KHUGEPAGED)); > - seq_buf_printf(&s, "pgsteal %lu\n", > + seq_buf_printf(s, "pgsteal %lu\n", > memcg_events(memcg, PGSTEAL_KSWAPD) + > memcg_events(memcg, PGSTEAL_DIRECT) + > memcg_events(memcg, PGSTEAL_KHUGEPAGED)); > @@ -1598,13 +1595,13 @@ static void memory_stat_format(struct mem_cgroup *memcg, char *buf, int bufsize) > memcg_vm_event_stat[i] == PGPGOUT) > continue; > > - seq_buf_printf(&s, "%s %lu\n", > + seq_buf_printf(s, "%s %lu\n", > vm_event_name(memcg_vm_event_stat[i]), > memcg_events(memcg, memcg_vm_event_stat[i])); > } > > /* The above should easily fit into one page */ > - WARN_ON_ONCE(seq_buf_has_overflowed(&s)); > + WARN_ON_ONCE(seq_buf_has_overflowed(s)); > } > > #define K(x) ((x) << (PAGE_SHIFT-10)) > @@ -1642,6 +1639,7 @@ 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]; > + struct seq_buf s; > > lockdep_assert_held(&oom_lock); > > @@ -1664,8 +1662,9 @@ 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(":"); > - memory_stat_format(memcg, buf, sizeof(buf)); > - pr_info("%s", buf); > + seq_buf_init(&s, buf, sizeof(buf)); > + memory_stat_format(memcg, &s); > + seq_buf_do_printk(&s, KERN_INFO); > } > > /* > @@ -6573,10 +6572,12 @@ static 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); > + struct seq_buf s; > > if (!buf) > return -ENOMEM; > - memory_stat_format(memcg, buf, PAGE_SIZE); > + seq_buf_init(&s, buf, PAGE_SIZE); > + memory_stat_format(memcg, &s); > seq_puts(m, buf); > kfree(buf); > return 0; > -- > 2.40.1.495.gc816e09b53d-goog -- Michal Hocko SUSE Labs