On 7/18/19 7:39 AM, Christopher Lameter wrote: > On Wed, 17 Jul 2019, Waiman Long wrote: > >> The show method of /sys/kernel/slab/<slab>/shrink sysfs file currently >> returns nothing. This is now modified to show the time of the last >> cache shrink operation in us. > What is this useful for? Any use cases? I got query about how much time will the slab_mutex be held when shrinking the cache. I don't have a solid answer as it depends on how many memcg caches are there. This patch is a partial answer to that as it give a rough upper bound of the lock hold time. >> CONFIG_SLUB_DEBUG depends on CONFIG_SYSFS. So the new shrink_us field >> is always available to the shrink methods. > Aside from minimal systems without CONFIG_SYSFS... Does this build without > CONFIG_SYSFS? The sysfs code in mm/slub.c is guarded by CONFIG_SLUB_DEBUG which, in turn, depends on CONFIG_SYSFS. So if CONFIG_SYSFS is off, the shrink sysfs methods will be off as well. I haven't tried doing a minimal build. I will certainly try that, but I don't expect any problem here. Cheers, Longman
