On Wed, Dec 11, 2024 at 11:09:56AM -0500, Johannes Weiner wrote: > This would work, but it seems somewhat complicated. The atomics in > memcg charging and the vmstat updates are batched, and the per-page > overhead is for the most part cheap per-cpu ops. Not an issue per se. OK, fair enough, I hadn't realised it was a percpu-refcount. Still, we might consume several batches (batch size of 64) when we could do it all in one shot. Perhaps you'd be more persuaded by: (a) If we clear __GFP_ACCOUNT then alloc_pages_bulk() will work, and that's a pretty significant performance win over calling alloc_pages() in a loop. (b) Once we get to memdescs, calling alloc_pages() with __GFP_ACCOUNT set is going to require allocating a memdesc to store the obj_cgroup in, so in the future we'll save an allocation. Your proposed alternative will work and is way less churn. But it's not preparing us for memdescs ;-)
