On Wed, May 05, 2021 at 11:29:54PM +0200, Vlastimil Babka wrote: > On 5/5/21 8:32 PM, Roman Gushchin wrote: > > On Wed, May 05, 2021 at 08:02:06PM +0200, Vlastimil Babka wrote: > >> On 5/5/21 7:30 PM, Roman Gushchin wrote: > >> > On Wed, May 05, 2021 at 11:46:13AM -0400, Waiman Long wrote: > >> >> > >> >> With this change, all the objcg pointer array objects will come from > >> >> KMALLOC_NORMAL caches which won't have their objcg pointer arrays. So > >> >> both the recursive kfree() problem and non-freeable slab problem are > >> >> gone. Since both the KMALLOC_NORMAL and KMALLOC_CGROUP caches no longer > >> >> have mixed accounted and unaccounted objects, this will slightly reduce > >> >> the number of objcg pointer arrays that need to be allocated and save > >> >> a bit of memory. > >> > > >> > Unfortunately the positive effect of this change will be likely > >> > reversed by a lower utilization due to a larger number of caches. > >> > > >> > Btw, I wonder if we also need a change in the slab caches merging procedure? > >> > KMALLOC_NORMAL caches should not be merged with caches which can potentially > >> > include accounted objects. > >> > >> Good point. But looks like kmalloc* caches are extempt from all merging in > >> create_boot_cache() via > >> > >> s->refcount = -1; /* Exempt from merging for now */ > > > > Wait, s->refcount is adjusted to 1 in create_kmalloc_cache() after calling > > into create_boot_cache? > > Hmm I missed that > > Now I wonder why all kmalloc caches on my system have 0 aliases :) > cat /sys/kernel/slab/kmalloc-*/aliases Yeah, I noticed it too, it's a good question. And I remember a case from the past when it wasn't true (kmalloc-32 was shared with something else).
