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Fri, 16 May 2025 09:30:17 +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 jqIfKakFJ2gNbgAAD6G6ig (envelope-from ); Fri, 16 May 2025 09:30:17 +0000 Message-ID: <050484a9-c08c-40d2-b431-76903a639222@suse.cz> Date: Fri, 16 May 2025 11:30:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/5] memcg: disable kmem charging in nmi for unsupported arch To: Shakeel Butt , Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Alexei Starovoitov , Sebastian Andrzej Siewior , Harry Yoo , Yosry Ahmed , Peter Zijlstra , Mathieu Desnoyers , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team References: <20250516064912.1515065-1-shakeel.butt@linux.dev> <20250516064912.1515065-2-shakeel.butt@linux.dev> Content-Language: en-US From: Vlastimil Babka In-Reply-To: <20250516064912.1515065-2-shakeel.butt@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Queue-Id: DA86F40008 X-Rspamd-Server: rspam09 X-Stat-Signature: q3my4fkwtzd37n1paxfkyi3c3py7gs4m X-HE-Tag: 1747387820-407891 X-HE-Meta: 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 7ts50H5p 4SmER3llMdq3u/I+1d+FOA0XsmQwZq03sMIQePnT8lj6kZOuv65zyk8MSCz+xIb+Jxgc4YlX2rlaBZalPW1PPjItKewNmZlPTXPPXVLyL1ELmDK7NqZSeUxHr+GwW5vtvYrEKONNqj1B/BJEgpjxhQLbmkjXGNIGWmW0txdfAezq0L4jUh852tIXCw/B7sphGAKwc+qPQZm/suNxxqQRCygpPbHNhONzuEPS4PXbe3H61O9fRgZLdTbtTErPx+SQwPhqHPJg+lw8pOCOuauY2wPx0yJcBPojWIcvd 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: List-Subscribe: List-Unsubscribe: On 5/16/25 08:49, Shakeel Butt wrote: > The memcg accounting and stats uses this_cpu* and atomic* ops. There are > archs which define CONFIG_HAVE_NMI but does not define > CONFIG_ARCH_HAS_NMI_SAFE_THIS_CPU_OPS and ARCH_HAVE_NMI_SAFE_CMPXCHG, so > memcg accounting for such archs in nmi context is not possible to > support. Let's just disable memcg accounting in nmi context for such > archs. > > Signed-off-by: Shakeel Butt > --- > include/linux/memcontrol.h | 5 +++++ > mm/memcontrol.c | 15 +++++++++++++++ > 2 files changed, 20 insertions(+) > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > index f7848f73f41c..53920528821f 100644 > --- a/include/linux/memcontrol.h > +++ b/include/linux/memcontrol.h > @@ -62,6 +62,11 @@ struct mem_cgroup_reclaim_cookie { > > #ifdef CONFIG_MEMCG > > +#if defined(CONFIG_ARCH_HAS_NMI_SAFE_THIS_CPU_OPS) || \ > + !defined(CONFIG_HAVE_NMI) || defined(ARCH_HAVE_NMI_SAFE_CMPXCHG) > +#define MEMCG_SUPPORTS_NMI_CHARGING > +#endif > + > #define MEM_CGROUP_ID_SHIFT 16 > > struct mem_cgroup_id { > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index e17b698f6243..dface07f69bb 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2647,11 +2647,26 @@ static struct obj_cgroup *current_objcg_update(void) > return objcg; > } > > +#ifdef MEMCG_SUPPORTS_NMI_CHARGING > +static inline bool nmi_charging_allowed(void) > +{ > + return true; > +} > +#else > +static inline bool nmi_charging_allowed(void) > +{ > + return false; > +} > +#endif > + > __always_inline struct obj_cgroup *current_obj_cgroup(void) > { > struct mem_cgroup *memcg; > struct obj_cgroup *objcg; > > + if (in_nmi() && !nmi_charging_allowed()) Exchange the two as the latter is compile-time constant, so it can shortcut the in_nmi() check away in all the good cases? > + return NULL; > + > if (in_task()) { > memcg = current->active_memcg; > if (unlikely(memcg))