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b=pZ9LaEnwtoMzE2wP2JePzB0UIbDFe/z9WwsqJMrJ6cu8/bpETlbYrY84oneD3Rkik eQQX0YSVwarX9f71FzDcafq2O+YLCxYZB6Wo1LRQZ9kkbJx25PobIAKjp3XyCr+4EQ uOyDZo9HbPpk8BUZm2PlqLrPbneIgJr0SFU4xMvNKThQDt9V9IsR2fLb9sqNFP4k8p Oyxdf3sZUU9P5Hw4UT3x0zX7fvyobkyNDnN+e+tX1I/rTHSs4xaXXu/na9egoDsvhv E2puVi41ZsqqSRvNPDLTV/OnRNmuoq1+j9Hfdr63UB+JEVNZDlCJU04xKKeF1UZj1O KbWaa4cLAs83Q== Message-ID: <1f19b775-d670-40ef-9147-2dcdce62b56e@kernel.org> Date: Fri, 28 Nov 2025 13:38:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Daniel Gomez Subject: Re: [PATCH V1] mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction To: Harry Yoo , surenb@google.com Cc: Liam.Howlett@oracle.com, atomlin@atomlin.com, bpf@vger.kernel.org, cl@gentwo.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, lucas.demarchi@intel.com, maple-tree@lists.infradead.org, mcgrof@kernel.org, petr.pavlu@suse.com, rcu@vger.kernel.org, rientjes@google.com, roman.gushchin@linux.dev, samitolvanen@google.com, sidhartha.kumar@oracle.com, urezki@gmail.com, vbabka@suse.cz, jonathanh@nvidia.com References: <20251128113740.90129-1-harry.yoo@oracle.com> Content-Language: en-US From: Daniel Gomez Organization: kernel.org In-Reply-To: <20251128113740.90129-1-harry.yoo@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspam-User: X-Rspamd-Queue-Id: 9F99740008 X-Stat-Signature: a94jzoxyzgistcttzj8wx6g671xsg81j X-HE-Tag: 1764333557-907922 X-HE-Meta: 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 Bhwo3iRw 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 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 28/11/2025 12.37, Harry Yoo wrote: > Currently, kvfree_rcu_barrier() flushes RCU sheaves across all slab > caches when a cache is destroyed. This is unnecessary when destroying > a slab cache; only the RCU sheaves belonging to the cache being destroyed > need to be flushed. > > As suggested by Vlastimil Babka, introduce a weaker form of > kvfree_rcu_barrier() that operates on a specific slab cache and call it > on cache destruction. > > The performance benefit is evaluated on a 12 core 24 threads AMD Ryzen > 5900X machine (1 socket), by loading slub_kunit module. > > Before: > Total calls: 19 > Average latency (us): 8529 > Total time (us): 162069 > > After: > Total calls: 19 > Average latency (us): 3804 > Total time (us): 72287 > > Link: https://lore.kernel.org/linux-mm/0406562e-2066-4cf8-9902-b2b0616dd742@kernel.org > Link: https://lore.kernel.org/linux-mm/e988eff6-1287-425e-a06c-805af5bbf262@nvidia.com > Link: https://lore.kernel.org/linux-mm/1bda09da-93be-4737-aef0-d47f8c5c9301@suse.cz > Suggested-by: Vlastimil Babka > Signed-off-by: Harry Yoo > --- Thanks Harry for the patch, A quick test on a different machine from the one I originally used to report this shows a decrease from 214s to 100s. LGTM, Tested-by: Daniel Gomez > > Not sure if the regression is worse on the reporters' machines due to > higher core count (or because some cores were busy doing other things, > dunno). FWIW, CI modules run on an 8 core VM. Depending on the host CPU, this made the absolute number different but equivalent performance degradation. > > Hopefully this will reduce the time to complete tests, > and Suren could add his patch on top of this ;) > > include/linux/slab.h | 5 ++++ > mm/slab.h | 1 + > mm/slab_common.c | 52 +++++++++++++++++++++++++++++------------ > mm/slub.c | 55 ++++++++++++++++++++++++-------------------- > 4 files changed, 73 insertions(+), 40 deletions(-)