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Mon, 7 Oct 2024 14:35:04 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id FYptIZjxA2elfAAAD6G6ig (envelope-from ); Mon, 07 Oct 2024 14:35:04 +0000 Message-ID: <1f958b18-331c-4290-a575-a9271162c361@suse.cz> Date: Mon, 7 Oct 2024 16:34:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: percpu: Increase PERCPU_DYNAMIC_SIZE_SHIFT on certain builds. To: Sebastian Andrzej Siewior , linux-mm@kvack.org, Andrew Morton Cc: Arnd Bergmann , Christoph Lameter , David Rientjes , Dennis Zhou , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Joonsoo Kim , Pekka Enberg , Roman Gushchin , Tejun Heo , Thomas Gleixner References: <20241007143049.gyMpEu89@linutronix.de> Content-Language: en-US From: Vlastimil Babka In-Reply-To: <20241007143049.gyMpEu89@linutronix.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Stat-Signature: 7n5x46dsxzgmrqqpe4978nn7b6zebhf8 X-Rspamd-Queue-Id: 76374120012 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1728311706-717098 X-HE-Meta: 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 SvYCYzLm Oq7O7TQYkvLJxrC/FyKmlqJanDNDUv3GyK/+VUL5qxWsV2NTMM/9lFJmf8zlhslkVSG5qTHTbP621aDurYF4Msuuy1wA+R46+SdVWRNMXp0t1p1g8Gg3pyPEmSGa25fLYgOMjR6xCHiMMoxf/1h4PS8Y4K0gYVrmpEZ/Po/3bd4bfjqCi3lQYL0SaqgcyHtVkBd18S2AJzpKSvlMOlJHQPKZw6NLNdRDhAPiWrIJUae34Dv1f3oIKTFktOWns/svuRpXppwcaX6HZK42HCjIWVBy7lT6OiG+e5OugiVKMyTwjTHWm+b+FUhFFDkoZcjjL8T6Io9mwmRI3X6xt42zIJBxF/RD2m5UovidkayT3W3QDYW6LkMUtaqJJUTuW7yK4IWizpy+RTNhZATDx7aKWZauqIlg1MpZnuhP1i9PPOEnMaJ3T6jroilz0zpdeTlvkrNO33KL5wkxvZEE= 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 10/7/24 4:30 PM, 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 IIRC Dennis at some point mentioned this will eventually become more robust as now it's kind of a whack-a-mole? :) But yeah, let's fix in a way that we can. Acked-by: Vlastimil Babka > --- > include/linux/percpu.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/include/linux/percpu.h b/include/linux/percpu.h > index b6321fc491598..52b5ea663b9f0 100644 > --- a/include/linux/percpu.h > +++ b/include/linux/percpu.h > @@ -41,7 +41,11 @@ > PCPU_MIN_ALLOC_SHIFT) > > #ifdef CONFIG_RANDOM_KMALLOC_CACHES > -#define PERCPU_DYNAMIC_SIZE_SHIFT 12 > +# if defined(CONFIG_LOCKDEP) && !defined(CONFIG_PAGE_SIZE_4KB) > +# define PERCPU_DYNAMIC_SIZE_SHIFT 13 > +# else > +# define PERCPU_DYNAMIC_SIZE_SHIFT 12 > +#endif /* LOCKDEP and PAGE_SIZE > 4KiB */ > #else > #define PERCPU_DYNAMIC_SIZE_SHIFT 10 > #endif