On Tue, 26 Apr 2022 00:59:37 -0600 Yu Zhao <yuzhao@xxxxxxxxxx> wrote: > On Fri, Apr 15, 2022 at 10:20 PM Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Fri, 15 Apr 2022 18:03:16 -0600 Yu Zhao <yuzhao@xxxxxxxxxx> wrote: > > > > > > Presumably sysfs is the place. Fully documented and with usage > > > > examples in the changelog so we can carefully review the proposed > > > > extensions to Linux's ABI. Extensions which must be maintained > > > > unchanged for all time. > > > > > > Eventually, yes. There still is a long way to go. Rest assured, this > > > is something Google will keep investing resources on. > > > > So. The plan is to put these interfaces in debugfs for now, with a > > view to migrating stabilized interfaces into sysfs (or procfs or > > whatever) once end-user requirements and use cases are better > > understood? > > The requirements are well understood and the use cases are proven, > e.g., Google [1], Meta [2] and Alibaba [3]. > > [1] https://dl.acm.org/doi/10.1145/3297858.3304053 > [2] https://dl.acm.org/doi/10.1145/3503222.3507731 > [3] https://gitee.com/anolis/cloud-kernel/blob/release-5.10/mm/kidled.c So will these interfaces be moved into sysfs? > > If so, that sounds totally great to me. But it should have been in > > the darn changelog! This is the sort of thing which we care about most > > keenly. > > > > It would be helpful for reviewers to understand the proposed timeline > > for this process, because the entire feature isn't really real until > > this is completed, is it? I do think we should get this nailed down > > relatively rapidly, otherwise people will be reluctant to invest much > > into a moving target. > > > > And I must say, I see dissonance between the overall maturity of the > > feature as described in these emails versus the immaturity of these > > userspace control interfaces. What's happening there? > > Very observant. To answer both of the questions above: each iteration > of the entire stack is a multi-year effort. > > Given its ROI, companies I know of constantly pour money into this > area. Given its scale, this debugfs is the least of their concerns. A > good example is the proactive reclaim sysfs interface [4]. It's been > used at Google for many years and at Meta for a few years. We only > started finalizing it recently. > > [4] https://lore.kernel.org/r/20220425190040.2475377-1-yosryahmed@xxxxxxxxxx/ Sure, if one organization is involved in both the userspace code and the kernel interfaces then the alteration of kernel interfaces can be handled in a coordinated fashion. But releasing interfaces to the whole world is a different deal. It's acceptable to say "this is in debugfs for now because it's a work in progress" but it sounds like mglru's interfaces are beyond that stage?
