On Tue, 4 Apr 2023 00:13:50 +0000 Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: > Upon running some proactive reclaim tests using memory.reclaim, we > noticed some tests flaking where writing to memory.reclaim would be > successful even though we did not reclaim the requested amount fully. > Looking further into it, I discovered that *sometimes* we over-report > the number of reclaimed pages in memcg reclaim. > > Reclaimed pages through other means than LRU-based reclaim are tracked > through reclaim_state in struct scan_control, which is stashed in > current task_struct. These pages are added to the number of reclaimed > pages through LRUs. For memcg reclaim, these pages generally cannot be > linked to the memcg under reclaim and can cause an overestimated count > of reclaimed pages. This short series tries to address that. > > Patches 1-2 are just refactoring, they add helpers that wrap some > operations on current->reclaim_state, and rename > reclaim_state->reclaimed_slab to reclaim_state->reclaimed. > > Patch 3 ignores pages reclaimed outside of LRU reclaim in memcg reclaim. > The pages are uncharged anyway, so even if we end up under-reporting > reclaimed pages we will still succeed in making progress during > charging. > > Do not let the diff stat deceive you, the core of this series is patch 3, > which has one line of code change. All the rest is refactoring and one > huge comment. > Wouldn't it be better to do this as a single one-line patch for backportability? Then all the refactoring etcetera can be added on later.
