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Sun, 13 Oct 2024 13:47:20 -0700 (PDT) Date: Sun, 13 Oct 2024 13:47:20 -0700 (PDT) From: David Rientjes To: Sebastian Andrzej Siewior cc: linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Arnd Bergmann , Christoph Lameter , Dennis Zhou , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Joonsoo Kim , Pekka Enberg , Roman Gushchin , Tejun Heo , Thomas Gleixner Subject: Re: [PATCH] mm: percpu: Increase PERCPU_DYNAMIC_SIZE_SHIFT on certain builds. In-Reply-To: <20241007143049.gyMpEu89@linutronix.de> Message-ID: References: <20241007143049.gyMpEu89@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspamd-Queue-Id: 56E658000A X-Stat-Signature: i15fpcnebu86rt6xftzwtgbo681hqfyd X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1728852432-568484 X-HE-Meta: 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 /mqgFOIB 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 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 Mon, 7 Oct 2024, Sebastian Andrzej Siewior wrote: > Arnd reported a build failure due to the BUILD_BUG_ON() statement in > alloc_kmem_cache_cpus(). The test > > PERCPU_DYNAMIC_EARLY_SIZE < NR_KMALLOC_TYPES * KMALLOC_SHIFT_HIGH * sizeof(struct kmem_cache_cpu) > > The factors that increase the right side of the equation: > - PAGE_SIZE > 4KiB increases KMALLOC_SHIFT_HIGH > - For the local_lock_t in kmem_cache_cpu: > - PREEMPT_RT adds an actual lock. > - LOCKDEP increases the size of the lock. > - LOCK_STAT adds additional bytes plus padding to the lockdep > structure. > > The net difference with and without PREEMPT_RT is 88 bytes for the > lock_lock_t, 96 bytes for kmem_cache_cpu due to additional padding. > This is enough to exceed the 80KiB limit with 16KiB page size - the 8KiB > page size is fine. > > Increase PERCPU_DYNAMIC_SIZE_SHIFT to 13 on configs with PAGE_SIZE larger > than 4KiB and LOCKDEP enabled. > > Fixes: d8fccd9ca5f9 ("arm64: Allow to enable PREEMPT_RT.") > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-kbuild-all/202410020326.iaZIteIx-lkp@intel.com/ > Reported-by: Arnd Bergmann > Closes: https://lore.kernel.org/20241004095702.637528-1-arnd@kernel.org > Acked-by: Arnd Bergmann > Signed-off-by: Sebastian Andrzej Siewior Acked-by: David Rientjes