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From: Kent Overstreet To: Roman Gushchin Cc: Suren Baghdasaryan , akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, corbet@lwn.net, void@manifault.com, peterz@infradead.org, juri.lelli@redhat.com, ldufour@linux.ibm.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, dennis@kernel.org, tj@kernel.org, muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org, pasha.tatashin@soleen.com, yosryahmed@google.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, andreyknvl@gmail.com, keescook@chromium.org, ndesaulniers@google.com, gregkh@linuxfoundation.org, ebiggers@google.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, cgroups@vger.kernel.org Subject: Re: [PATCH 00/40] Memory allocation profiling Message-ID: References: <20230501165450.15352-1-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 5j4k7gmhzca66uanittkfkyny8xem4u7 X-Rspamd-Queue-Id: 130061C001B X-HE-Tag: 1682969890-468796 X-HE-Meta: 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 iLNE0kqS OPsnnVwScyh9tmBGt/fQbEQIjY7W/5+U2UwV/PCQ22sYaccDVtH/08lUgJ5CVurZFs+UjjJ6GI3Jw/r3Nb0HkOo02JrR8HzB5oM8DmYuZj+KRM91iBO2cSWkSeA== 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 Mon, May 01, 2023 at 11:14:45AM -0700, Roman Gushchin wrote: > It's a good idea and I generally think that +25-35% for kmalloc/pgalloc > should be ok for the production use, which is great! > In the reality, most workloads are not that sensitive to the speed of > memory allocation. :) My main takeaway has been "the slub fast path is _really_ fast". No disabling of preemption, no atomic instructions, just a non locked double word cmpxchg - it's a slick piece of work. > > For kmalloc, the overhead is low because after we create the vector of > > slab_ext objects (which is the same as what memcg_kmem does), memory > > profiling just increments a lazy counter (which in many cases would be > > a per-cpu counter). > > So does kmem (this is why I'm somewhat surprised by the difference). > > > memcg_kmem operates on cgroup hierarchy with > > additional overhead associated with that. I'm guessing that's the > > reason for the big difference between these mechanisms but, I didn't > > look into the details to understand memcg_kmem performance. > > I suspect recent rt-related changes and also the wide usage of > rcu primitives in the kmem code. I'll try to look closer as well. Happy to give you something to compare against :)