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Mon, 17 Mar 2025 20:56:39 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id TRyVH4eM2GddYQAAD6G6ig (envelope-from ); Mon, 17 Mar 2025 20:56:39 +0000 Message-ID: <7d50a14a-edfb-410d-840e-17876806a63b@suse.cz> Date: Mon, 17 Mar 2025 21:56:39 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 7/9] memcg: use __mod_memcg_state in drain_obj_stock Content-Language: en-US To: Shakeel Butt , Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Sebastian Andrzej Siewior , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team References: <20250315174930.1769599-1-shakeel.butt@linux.dev> <20250315174930.1769599-8-shakeel.butt@linux.dev> From: Vlastimil Babka In-Reply-To: <20250315174930.1769599-8-shakeel.butt@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.998]; MIME_GOOD(-0.10)[text/plain]; RCPT_COUNT_SEVEN(0.00)[11]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_DN_SOME(0.00)[] X-Spam-Score: -4.30 X-Spam-Flag: NO On 3/15/25 18:49, Shakeel Butt wrote: > For non-PREEMPT_RT kernels, drain_obj_stock() is always called with irq > disabled, so we can use __mod_memcg_state() instead of > mod_memcg_state(). For PREEMPT_RT, we need to add memcg_stats_[un]lock > in __mod_memcg_state(). > > Signed-off-by: Shakeel Butt > Reviewed-by: Sebastian Andrzej Siewior I've asked in the RFC and from Sebastian's answer I think my question was misunderstod, so let me try again. After this patch we'll have from mod_memcg_state(): mod_memcg_state() local_irq_save(flags); __mod_memcg_state() memcg_stats_lock(); <- new and unnecessary? Instead of modifying __mod_memcg_state() we could be more targetted and just do in drain_obj_stock(): memcg_stats_lock(); __mod_memcg_state(); memcg_stats_unlock(); Am I missing something? > --- > mm/memcontrol.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 3c4de384b5a0..dfe9c2eb7816 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -707,10 +707,12 @@ void __mod_memcg_state(struct mem_cgroup *memcg, enum memcg_stat_item idx, > if (WARN_ONCE(BAD_STAT_IDX(i), "%s: missing stat item %d\n", __func__, idx)) > return; > > + memcg_stats_lock(); > __this_cpu_add(memcg->vmstats_percpu->state[i], val); > val = memcg_state_val_in_pages(idx, val); > memcg_rstat_updated(memcg, val); > trace_mod_memcg_state(memcg, idx, val); > + memcg_stats_unlock(); > } > > #ifdef CONFIG_MEMCG_V1 > @@ -2845,7 +2847,7 @@ static void drain_obj_stock(struct memcg_stock_pcp *stock) > > memcg = get_mem_cgroup_from_objcg(old); > > - mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages); > + __mod_memcg_state(memcg, MEMCG_KMEM, -nr_pages); > memcg1_account_kmem(memcg, -nr_pages); > if (!mem_cgroup_is_root(memcg)) > memcg_uncharge(memcg, nr_pages);