On Mon, Mar 25, 2024 at 09:20:32AM +0100, Vlastimil Babka wrote: > The MEMCG_KMEM integration with slab currently relies on two hooks > during allocation. memcg_slab_pre_alloc_hook() determines the objcg and > charges it, and memcg_slab_post_alloc_hook() assigns the objcg pointer > to the allocated object(s). > > As Linus pointed out, this is unnecessarily complex. Failing to charge > due to memcg limits should be rare, so we can optimistically allocate > the object(s) and do the charging together with assigning the objcg > pointer in a single post_alloc hook. In the rare case the charging > fails, we can free the object(s) back. > > This simplifies the code (no need to pass around the objcg pointer) and > potentially allows to separate charging from allocation in cases where > it's common that the allocation would be immediately freed, and the > memcg handling overhead could be saved. > > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Link: https://lore.kernel.org/all/CAHk-=whYOOdM7jWy5jdrAm8LxcgCMFyk2bt8fYYvZzM4U-zAQA@xxxxxxxxxxxxxx/ > Reviewed-by: Roman Gushchin <roman.gushchin@xxxxxxxxx> > Reviewed-by: Chengming Zhou <chengming.zhou@xxxxxxxxx> > Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
