| Message ID | 20241007143049.gyMpEu89@linutronix.de (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: percpu: Increase PERCPU_DYNAMIC_SIZE_SHIFT on certain builds. | expand |
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 <lkp@intel.com> > Closes: https://lore.kernel.org/oe-kbuild-all/202410020326.iaZIteIx-lkp@intel.com/ > Reported-by: Arnd Bergmann <arnd@kernel.org> > Closes: https://lore.kernel.org/20241004095702.637528-1-arnd@kernel.org > Acked-by: Arnd Bergmann <arnd@arndb.de> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> 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 <vbabka@suse.cz> > --- > 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
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 <lkp@intel.com> > Closes: https://lore.kernel.org/oe-kbuild-all/202410020326.iaZIteIx-lkp@intel.com/ > Reported-by: Arnd Bergmann <arnd@kernel.org> > Closes: https://lore.kernel.org/20241004095702.637528-1-arnd@kernel.org > Acked-by: Arnd Bergmann <arnd@arndb.de> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Acked-by: David Rientjes <rientjes@google.com>
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
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 <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202410020326.iaZIteIx-lkp@intel.com/ Reported-by: Arnd Bergmann <arnd@kernel.org> Closes: https://lore.kernel.org/20241004095702.637528-1-arnd@kernel.org Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- include/linux/percpu.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)