Messages in this thread | | | Date | Thu, 29 Aug 2013 11:36:10 -0700 | From | Dave Hansen <> | Subject | Re: [PATCH] Avoid useless inodes and dentries reclamation |
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The new shrinker infrastructure in mmotm looks like it will make this problem worse.
old code: shrink_slab() for_each_shrinker { do_shrinker_shrink(); // one per batch prune_super() grab_super_passive() } }
Which means we've got at _most_ one grab_super_passive() per batch. The new code is something like this:
shrink_slab() { list_for_each_entry(shrinker, &shrinker_list, list) { for_each_node_mask(... shrinkctl->nodes_to_scan) { shrink_slab_node() } } }
shrink_slab_node() { max_pass = shrinker->count_objects(shrinker, shrinkctl); // ^^ does grab_super_passive() ... while (total_scan >= batch_size) { ret = shrinker->scan_objects(shrinker, shrinkctl); // ^^ does grab_super_passive() } }
We've got an extra grab_super_passive()s in the case where we are actually doing a scan, plus we've got the extra for_each_node_mask() loop. That means even more lock acquisitions in the multi-node NUMA case, which is exactly where we want to get rid of global lock acquisitions.
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