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Thu, 17 Sep 2026 09:25:34 -0700 (PDT) X-Relaying-Domain: everpuredata.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 1A53034014B; Thu, 17 Sep 2026 09:25:33 -0700 (PDT) From: Tim Menninger To: Harry Yoo Cc: linux-mm@kvack.org, Chuck Lever , linux-nfs@vger.kernel.org, Jon Curley , Eric Badger , Vlastimil Babka , Andrew Morton , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [SLUB] nfs_page cmpxchg_double_fail and perf lock perturbation on dual-socket NFS/RDMA Date: Thu, 17 Sep 2026 16:25:33 +0000 Message-Id: <20260917162533.600472-1-tmenninger@everpuredata.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit It reproduces with slab_nomerge. I booted the same kernel with: $ cat /proc/cmdline ... slab_nomerge ... Uninstrumented throughput remains in the high-45 to low-46 GB/s range, as before. During perf lock it was around 30 GB/s in these runs, versus roughly 25 GB/s previously. The dominant lock measurements are essentially unchanged: default slab_nomerge unpinned/node0 contentions 4,782,839 4,858,759 total wait 14.39 min 14.26 min average wait 180.47 us 176.13 us node0/node0 contentions 4,582,012 4,686,729 total wait 14.13 min 14.34 min average wait 185.05 us 183.53 us unpinned/balanced contentions 4,572,196 4,544,677 total wait 12.81 min 12.56 min average wait 168.14 us 165.84 us The uninstrumented cmpxchg_double_fail deltas were: default slab_nomerge unpinned/node0 7,471 8,892 node0/node0 713 457 unpinned/balanced 1,503 1,504 The CPU-utilization change while perf lock is active also remains. System-wide %idle for uninstrumented/instrumented windows was: default slab_nomerge uninstr. instr. uninstr. instr. unpinned/node0 31.46% 3.60% 23.02% 2.15% node0/node0 84.26% 12.07% 84.62% 11.85% unpinned/balanced 66.86% 14.83% 66.58% 14.78% Thanks, Tim