On Wed, Jan 24, 2024 at 09:46:23AM -0800, T.J. Mercier wrote: > In the meantime, instead of a revert how about changing the batch size > geometrically instead of the SWAP_CLUSTER_MAX constant: > > reclaimed = try_to_free_mem_cgroup_pages(memcg, > - min(nr_to_reclaim - > nr_reclaimed, SWAP_CLUSTER_MAX), > + (nr_to_reclaim - nr_reclaimed)/2, > GFP_KERNEL, reclaim_options); > > I think that should address the overreclaim concern (it was mentioned > that the upper bound of overreclaim was 2 * request), and this should > also increase the reclaim rate for root reclaim with MGLRU closer to > what it was before. Hahaha. Would /4 work for you? I genuinely think the idea is worth a shot. /4 would give us a bit more margin for error, since the bailout/fairness cutoffs have changed back and forth over time. And it should still give you a reasonable convergence on MGLRU. try_to_free_reclaim_pages() already does max(nr_to_reclaim, SWAP_CLUSTER_MAX) which will avoid the painful final approach loops the integer division would produce on its own. Please add a comment mentioning the compromise between the two reclaim implementations though.
