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McKenney" , Ingo Molnar Date: Wed, 02 Jul 2025 15:58:28 +0200 In-Reply-To: <26df8965-a430-4be3-a523-d292905f32fa@efficios.com> References: <202506251555.de6720f7-lkp@intel.com> <26df8965-a430-4be3-a523-d292905f32fa@efficios.com> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0ByZWRoYXQuY29tPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmbiuWMCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfJzZgD/TXjnqCyqaZH/Y2w+YVbvm93WX2eqBqiVZ6VEjTuGNs8A/iPrKbzdWC7AicnK xyhmqeUWOzFx5P43S1E1dhsrLWgP User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: gmQIReotumz1oiJskk3aaP2jZwFvzi1AvANGJNsi_s0_1751464805 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: ohfckdr1rrktud3j7jmkhpkxqfbpjzi7 X-Rspamd-Queue-Id: 1A324C0017 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1751464807-78117 X-HE-Meta: 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 pRl0q0wt d7wzaxhz1Q8v6WekTbP3U8x0xX8Qc4532omKBfFdmDFz00z3qNlgPfKIWNyW8zVJLsG2CRdWbIF25/uPLn3DlG0GwcN6V643tk83SCa13ljb7n4pGzrCYxvltE6jDgoVo4q+DScFRQKgNyyZcEwKiXK7sTIvhtKuSUlz9R7VUMTfvwYU/CDcgbLWOgeAnpBbff978bowtgwnrfX/lPzO3+G1SxPtAf/thUsmyA/Opw0BKIA5MXasPF0fgI6pKt9x7HP+PLRzRenh6TC7B+g6q5I9xwyvrL2w3VsUd6WSabSemNlkpDUZE1m8xr5CU1tzLcWdxy4twH5ty/IhCmdqr1LI+MS6h9koPnbLWk19xeJt+WvhH6ieqHUxB+Cw4UHny/DZ99sEct59cuLE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Wed, 2025-06-25 at 09:57 -0400, Mathieu Desnoyers wrote: > On 2025-06-25 04:01, kernel test robot wrote: > >=20 > > Hello, > >=20 > > kernel test robot noticed a 10.1% regression of > > hackbench.throughput on: >=20 > Hi Gabriele, >=20 > This is a significant regression. Can you investigate before it gets > merged ? >=20 Hi Mathieu, I run some tests, the culprit for this performance regression seems to be the interference due to more consistent `mm_cid` scans and them running in `work_struct`, which brings some more scheduling overhead. One solution could be to reduce the frequency: now they run (sporadically) about every 100ms, if the minimum delay is 1s, the test results seem ok. However, I tried another approach that seems promising: work_struct get scheduled relatively fast and this ends up giving a lot of contention with kworkers, however something like timer_list seems less aggressive and we obtain a similar reliability with respect to calls to the mm_cid scan, without the same performance impact. At the moment I just kept roughly the same structure of the patch and used a timer delayed by 1 jiffy in place of the work_struct. It may look cleaner if we use the timer directly for the 100ms delay instead of storing and checking the time, in fact running a scan about 100ms after every rseq_handle_notify_resume. What do you think? Thanks, Gabriele