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Mon, 14 Sep 2026 10:40:00 -0700 (PDT) X-Relaying-Domain: purestorage.com Received: from irdv-tmenninger.dev.purestorage.com (irdv-tmenninger.dev.purestorage.com [10.32.149.15]) by c14-smtp-2023.dev.purestorage.com (Postfix) with ESMTPS id 0736C340245; Mon, 14 Sep 2026 10:39:59 -0700 (PDT) From: tmenninger@purestorage.com To: Chuck Lever Cc: Trond Myklebust , Anna Schumaker , Tejun Heo , Lai Jiangshan , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, Eric Badger , Jon Curley Subject: Re: [PATCH RFC 6/8] SUNRPC: Reduce rpciod workqueue contention Date: Mon, 14 Sep 2026 17:39:58 +0000 Message-Id: <20260914173958.2045683-1-tmenninger@purestorage.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <611738b5-e115-4531-8d08-62607dc7f8ff@slotpi15m67> References: <611738b5-e115-4531-8d08-62607dc7f8ff@slotpi15m67> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > The lock profile did not move. free_slowpath fell by four orders > of magnitude and __slab_free took list_lock just as often. So the > list_lock contention is not the remote frees, and it never was! Aha! Okay, thank you for all of your time and help with this. If I am understanding correctly, the SLUB/barn/sheaf behavior we are looking at here is pre-existing rather than introduced by this series. The SMT affinity change is what changes the placement enough to expose the remote-free cost on this workload. > - Total and average wait for the list_lock address in the pinned > run. The unpinned run showed 5.05 min and 90 us average; if the > pinned run is similar, the lock absorbs the same time whichever > way the frees go. For the node0-pinned run, filtering the dominant lock gave: 2,907,948 3.37 min 69.62 us __slab_free 269,174 23.00 sec 85.46 us get_partial_node_bulk 175,965 15.17 sec 86.22 us __refill_objects_node So in total that is about 3.353M contentions, 4.01 minutes of aggregate wait, and roughly 71.8 us average wait. Compared with the unpinned run: unpinned node0 pinned contentions 3.346M 3.353M aggregate wait 5.05 min ~4.01 min average wait 90.48 us ~71.8 us So the contention count is essentially unchanged even though free_slowpath drops from ~70M to ~9K. The pinned case does have somewhat lower wait time per contention. > - mpstat idle for node 0 in both runs, to tell whether that wait > is idle time being spent or throughput being lost. Averaging the node0 CPUs (0-23,48-71) in that sample gives about 66% idle. In the earlier unpinned/all-local bad-state samples, those CPUs were nearly saturated, generally around 0-2% idle. > - Throughput for the node 0 / node 0 run that produced the counter > table above. It is the one configuration missing from your > throughput table. Oh yeah, it was the same trend as the workload table below: unpinned was 43.4 GB/s and node 0 pinned was 46.5 GB/s. At this point I think we have a reasonably clear separation between the pre-existing allocator behavior and the regression introduced by the SMT affinity change. I don't have any additional data I think would materially change that conclusion, but I'm happy to run any targeted follow-up you think would still be useful.