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Wed, 05 Mar 2025 03:07:25 -0800 (PST) MIME-Version: 1.0 References: <20250228-mm-selftests-v3-0-958e3b6f0203@google.com> <20250228-mm-selftests-v3-6-958e3b6f0203@google.com> In-Reply-To: <20250228-mm-selftests-v3-6-958e3b6f0203@google.com> From: Brendan Jackman Date: Wed, 5 Mar 2025 12:07:14 +0100 X-Gm-Features: AQ5f1JqnX0ORyymHsw5kQxZqiZ_jVU2MAEIa8yR0CC4Q6dLgX8mYcADTJ_z6BII Message-ID: Subject: Re: [PATCH v3 06/10] selftests/mm: Don't fail uffd-stress if too many CPUs To: Lorenzo Stoakes , Andrew Morton , Shuah Khan Cc: Dev Jain , linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Mateusz Guzik Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: 4kip48fsgzocwgqefjumtg8gcodpoxod X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 08DB61C0015 X-Rspam-User: X-HE-Tag: 1741172847-928844 X-HE-Meta: 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 EQaFw8+b 3sO40LLAIaBo/y9I8Vp26DpuG7b0M/dT2Gc361D47PNClbBs48PAqgXWDwIzQpV8HxYJtZZPnPTLIUxXMsp2v2f0rZi3iBGqCkeB5RnBvPBwFU0tWvZIHFva4BWU/pE/CdiU4cyVA20i60tDbVxt8JBsR27Yz/IjeXrTh8STa2Pm2U5AKmfc8+Z4ccft9Q/fElmRCeFfykD1uLA1M7p3tQtvEDWrQITdFdgFySMYCNmbtUrc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.105235, 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 Fri, 28 Feb 2025 at 17:55, Brendan Jackman wrote: > > This calculation divides a fixed parameter by an environment-dependent > parameter i.e. the number of CPUs. > > The simple way to avoid machine-specific failures here is to just put a > cap on the max value of the latter. > > Suggested-by: Mateusz Guzik > Signed-off-by: Brendan Jackman > --- > tools/testing/selftests/mm/uffd-stress.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/tools/testing/selftests/mm/uffd-stress.c b/tools/testing/selftests/mm/uffd-stress.c > index efe2051c393096e237d942c04a264b6611a6e127..5656128590373ed376b3b5d9259e5ca3867a4099 100644 > --- a/tools/testing/selftests/mm/uffd-stress.c > +++ b/tools/testing/selftests/mm/uffd-stress.c > @@ -434,6 +434,7 @@ static void sigalrm(int sig) > > int main(int argc, char **argv) > { > + unsigned long nr_cpus; > size_t bytes; > > if (argc < 4) > @@ -452,7 +453,15 @@ int main(int argc, char **argv) > return KSFT_SKIP; > } > > - nr_threads = sysconf(_SC_NPROCESSORS_ONLN); > + nr_cpus = sysconf(_SC_NPROCESSORS_ONLN); > + if (nr_cpus > 32) { > + /* Don't let calculation below go to zero. */ > + ksft_print_msg("_SC_NPROCESSORS_ONLN (%lu) too large, capping nr_threads to 32\n", > + nr_cpus); > + nr_threads = 32; > + } else { > + nr_cpus = nr_threads; Won't have time to send v4 for a few days so I'll just note here: this shoudl be nr_thread = nr_cpus. This causes a division by zero on machines with less than 30 CPUs.