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b=fxinpcWicIgDP/jjCLvgA8QAhRzHwuNnSTLNbHpNh7LOH+bC8AKIalAivbk0uMKKF dq+RbDNdaq6+GAW3+9qNFnDX9vYtSZht/5yHP+dgTYUJP4wenFJC/MiN6gt6Jg7xkc ISZPm8IbCFH0pwDulPD0PyQ2NNs5JfmHxBhexRTXQ7e6Rc3vG8LcisZlpTTSIVO3mo SehVfsInq5CECU/dl9kI5KgqF7af4YS/fdr8H6RxsS5ti97gEXFEsoj55QGYVMjZVx PkVik3ugjSSi4yLzqifdDrlVkw0mGRTCbfWnbyRnyeKpqNtn4gxba7Dqb4BAF1PRRh gY5/EPm9Kx3/w== Message-ID: Date: Wed, 13 May 2026 17:00:35 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] selftests/mm: add zone->lock tracepoint verification test To: "David Hildenbrand (Arm)" , Andrew Morton , linux-mm@kvack.org Cc: Vlastimil Babka , Steven Rostedt , Suren Baghdasaryan , Michal Hocko , Zi Yan , Lorenzo Stoakes , Shuah Khan , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kernel-team@cloudflare.com References: <20260508162207.3315781-1-hawk@kernel.org> <20260508162207.3315781-2-hawk@kernel.org> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 36EE740009 X-Stat-Signature: h11tqo3rinqsy7w4aoc8z3oh4oajnt7n X-Rspam-User: X-HE-Tag: 1778684441-91127 X-HE-Meta: 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 VqsTMGiw hYY1lXM9BLOTehd6YIMOQ2XIiEwREXr+IxD+J0dL7QttA6ud9dXxy2JNS11nFgr8i5ACZfwoCu44hziknKqGMsCGm0+pZaPsnche+Q6YBRlPvHBllAKOgFp1UVKRWznNypmQRTCRshL3l8BFMpp0129i/cYI3NscDRCMebloOmhei7+ORqKxSGvBeyCyMCmEqn3u3r5rW5YyolKy/NeKS+TNtnd5gA0Ff+LNENJYLEKgx0j8qhX9XGp6vwWoklF+Lg7nFel2N3K+8FQlC4fIUXIObow== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 08/05/2026 22.15, David Hildenbrand (Arm) wrote: > On 5/8/26 18:22, hawk@kernel.org wrote: >> From: Jesper Dangaard Brouer >> >> Add a selftest to verify the kmem:mm_zone_lock_contended, >> kmem:mm_zone_locked, and kmem:mm_zone_lock_unlock tracepoints. >> >> The test has two components: >> >> zone_lock_contention.c - a workload that spawns threads doing rapid >> page allocation and freeing to generate zone->lock contention. It >> shrinks PCP lists via percpu_pagelist_high_fraction to force frequent >> free_pcppages_bulk() and rmqueue_bulk() calls. >> >> test_zone_lock_tracepoints.sh - uses bpftrace to verify tracepoints >> exist, have the expected fields, fire under load, and that wait_ns >> is populated when contention occurs. >> >> Signed-off-by: Jesper Dangaard Brouer >> --- >> tools/testing/selftests/mm/Makefile | 2 + >> .../mm/test_zone_lock_tracepoints.sh | 212 ++++++++++++++++++ >> .../selftests/mm/zone_lock_contention.c | 166 ++++++++++++++ > > This really looks excessive and ... not really how we usually treat tracepoints? > > I don't know about others, but I don't think this is really what we want as a MM > selftest. > I wanted to have a program that tested the code I changed, so I simply made AI write a verification test and asked it to create as a selftest, that I've run to verify my code change was correctly implemented. As I needed to trigger lock contention the test is more advanced, but luckily AI solved it in only the 2nd attempt. It makes sense to drop this patch. We shouldn't keep this code in the kernel tree, it simply verified that my code works. There is little chance that this test will catch meaningful regressions for these tracepoints. --Jesper