On Wed, Nov 8, 2023 at 12:22 AM Huan Yang <link@xxxxxxxx> wrote: > > > 在 2023/11/8 16:14, Yosry Ahmed 写道: > > On Wed, Nov 8, 2023 at 12:11 AM Huang, Ying <ying.huang@xxxxxxxxx> wrote: > >> Huan Yang <link@xxxxxxxx> writes: > >> > >>> HI Huang, Ying > >>> > >>> Thanks for reply. > >>> > >>> 在 2023/11/8 15:35, Huang, Ying 写道: > >>>> Huan Yang <link@xxxxxxxx> writes: > >>>> > >>>>> In some cases, we need to selectively reclaim file pages or anonymous > >>>>> pages in an unbalanced manner. > >>>>> > >>>>> For example, when an application is pushed to the background and frozen, > >>>>> it may not be opened for a long time, and we can safely reclaim the > >>>>> application's anonymous pages, but we do not want to touch the file pages. > >>>>> > >>>>> This patchset extends the proactive reclaim interface to achieve > >>>>> unbalanced reclamation. Users can control the reclamation tendency by > >>>>> inputting swappiness under the original interface. Specifically, users > >>>>> can input special values to extremely reclaim specific pages. > >>>> From mem_cgroup_swappiness(), cgroupv2 doesn't have per-cgroup > >>>> swappiness. So you need to add that firstly? > >>> Sorry for this mistake, we always work on cgroupv1, so, not notice > >>> this commit 4550c4e, thank your for point that. > >>> > >>> I see this commit comment that `that's a different discussion`, but, > >>> to implements this, I will try add. > >>> > >>>>> Example: > >>>>> echo "1G" 200 > memory.reclaim (only reclaim anon) > >>>>> echo "1G" 0 > memory.reclaim (only reclaim file) > >>>>> echo "1G" 1 > memory.reclaim (only reclaim file) > >>>>> > >>>>> Note that when performing unbalanced reclamation, the cgroup swappiness > >>>>> will be temporarily adjusted dynamically to the input value. Therefore, > >>>>> if the cgroup swappiness is further modified during runtime, there may > >>>>> be some errors. > >>>> If cgroup swappiness will be adjusted temporarily, why not just change > >>>> it via a script before/after proactive reclaiming? > >>> IMO, this unbalance reclaim only takes effect for a single command, > >>> so if it is pre-set using a script, the judgment of the reclamation tendency > >>> may become complicated. > >> If swappiness == 0, then we will only reclaim file pages. If swappiness > >> == 200, then we may still reclaim file pages. So you need a way to > >> reclaim only anon pages? > >> > >> If so, can we use some special swappiness value to specify that? I > >> don't know whether use 200 will cause regression. If so, we may need > >> some other value, e.g. >= 65536. > > I don't think swappiness is the answer here. This has been discussed a > > while back, please see my response. As you mentioned, swappiness may > > be ignored by the kernel in some cases, and its behavior has > > historically changed before. > > For type base, reclaim can have direct tendencies as well. It's good. > But, what if > we only want to make small adjustments to the reclamation ratio? > Of course, sometimes swappiness may become ineffective. > Is there a real use case for this? I think it's difficult to reason about swappiness and make small adjustments to the file/anon ratio based on it. I'd prefer a more concrete implementation.
