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Wed, 30 Aug 2023 01:22:02 -0700 (PDT) MIME-Version: 1.0 References: <89c2f64120a7dd6b2255a9a281603359a50cf6f7.1693328501.git.andreyknvl@google.com> In-Reply-To: <89c2f64120a7dd6b2255a9a281603359a50cf6f7.1693328501.git.andreyknvl@google.com> From: Alexander Potapenko Date: Wed, 30 Aug 2023 10:21:25 +0200 Message-ID: Subject: Re: [PATCH 05/15] stackdepot: use fixed-sized slots for stack records To: andrey.konovalov@linux.dev Cc: Marco Elver , Andrey Konovalov , Dmitry Vyukov , Vlastimil Babka , kasan-dev@googlegroups.com, Evgenii Stepanov , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Konovalov Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: gabpy7ptu7s95z3wus3xpyqmrzjaf6q6 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 46F3412001F X-Rspam-User: X-HE-Tag: 1693383723-337182 X-HE-Meta: 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 X8cZl38z kpAHiE7F1qgW1mCKU/qE/PQqLfRqvLLJZllZ5l3R/H3qee2rfG5Z/PrAn4XGLd3gGT1DS6rr2JtwCf+WxYLR6+6lD59f8rLkf9zTegqLTMIYRpkNEJ2fuqg5jhZKJOJDWJcsIk7ThSFdhPMUMyt1v3M2k5pSomTZ+twv0dj7SNhV4dlodTxYaEj/QWBEHhUD7yccmUFzOZ49aoEUD5cLNuy6KQKTW2GrX13Pa1SjEifzIwonczkucTD3lWA1EU4HI0W2dklKjHKsIU7jryLlvxQsRrW90N2tAv1dwD/GHq1kWer1yet6Spo+KHTu/DKK7YADi+uQ35QtLrC2gtg3a0SIYd4P+B0h3v+RjWNXqlar7vCg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.006201, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Aug 29, 2023 at 7:11=E2=80=AFPM wrote: > > From: Andrey Konovalov > > Instead of storing stack records in stack depot pools one right after > another, use 32-frame-sized slots. I am slightly concerned about the KMSAN use case here, which defines KMSAN_STACK_DEPTH to 64. I don't have a comprehensive stack depth breakdown, but a quick poking around syzkaller.appspot.com shows several cases where the stacks are actually longer than 32 frames. Can you add a config parameter for the stack depth instead of mandating 32 frames everywhere? As a side note, kmsan_internal_chain_origin() (https://elixir.bootlin.com/linux/latest/source/mm/kmsan/core.c#L214) creates small 3-frame records in the stack depot to link two stacks together, which will add unnecessary stackdepot pressure. But this can be fixed by storing both the new stack trace and the link to the old stack trace in the same record.