* Re: [PATCH V1] mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction [not found] ` <20251128113740.90129-1-harry.yoo@oracle.com> @ 2025-12-02 9:29 ` Jon Hunter 2025-12-02 10:18 ` Harry Yoo 0 siblings, 1 reply; 2+ messages in thread From: Jon Hunter @ 2025-12-02 9:29 UTC (permalink / raw) To: Harry Yoo, surenb Cc: Liam.Howlett, atomlin, bpf, cl, da.gomez, linux-kernel, linux-mm, linux-modules, lucas.demarchi, maple-tree, mcgrof, petr.pavlu, rcu, rientjes, roman.gushchin, samitolvanen, sidhartha.kumar, urezki, vbabka, linux-tegra@vger.kernel.org On 28/11/2025 11:37, 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 <vbabka@suse.cz> > Signed-off-by: Harry Yoo <harry.yoo@oracle.com> > --- Thanks for the rapid fix. I have been testing this and can confirm that this does fix the performance regression I was seeing. BTW shouldn't we add a 'Fixes:' tag above? I would like to ensure that this gets picked up for v6.18 stable. Otherwise ... Tested-by: Jon Hunter <jonathanh@nvidia.com> Thanks! Jon -- nvpublic ^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH V1] mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction 2025-12-02 9:29 ` [PATCH V1] mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction Jon Hunter @ 2025-12-02 10:18 ` Harry Yoo 0 siblings, 0 replies; 2+ messages in thread From: Harry Yoo @ 2025-12-02 10:18 UTC (permalink / raw) To: Jon Hunter Cc: surenb, Liam.Howlett, atomlin, bpf, cl, da.gomez, linux-kernel, linux-mm, linux-modules, lucas.demarchi, maple-tree, mcgrof, petr.pavlu, rcu, rientjes, roman.gushchin, samitolvanen, sidhartha.kumar, urezki, vbabka, linux-tegra@vger.kernel.org On Tue, Dec 02, 2025 at 09:29:17AM +0000, Jon Hunter wrote: > > On 28/11/2025 11:37, 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 <vbabka@suse.cz> > > Signed-off-by: Harry Yoo <harry.yoo@oracle.com> > > --- > > Thanks for the rapid fix. I have been testing this and can confirm that this > does fix the performance regression I was seeing. Great! > BTW shouldn't we add a 'Fixes:' tag above? I would like to ensure that this > gets picked up for v6.18 stable. Good point, I added Cc: stable and Fixes: tags. (and your and Daniel's Reported-and-tested-by: tags) > Otherwise ... > > Tested-by: Jon Hunter <jonathanh@nvidia.com> Thank you Jon and Daniel a lot for reporting regression and testing the fix! -- Cheers, Harry / Hyeonggon ^ permalink raw reply [flat|nested] 2+ messages in thread
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[not found] ` <20251128113740.90129-1-harry.yoo@oracle.com>
2025-12-02 9:29 ` [PATCH V1] mm/slab: introduce kvfree_rcu_barrier_on_cache() for cache destruction Jon Hunter
2025-12-02 10:18 ` Harry Yoo
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