On Tue, Apr 18, 2023 at 07:54:01AM -0700, Suren Baghdasaryan wrote: > On Tue, Apr 18, 2023 at 7:25 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > On Mon, Apr 17, 2023 at 04:17:45PM -0700, Suren Baghdasaryan wrote: > > > On Mon, Apr 17, 2023 at 3:52 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > > > > > On Mon, Apr 17, 2023 at 03:40:33PM -0400, Peter Xu wrote: > > > > > > /* > > > > > > - * We don't do accounting for some specific faults: > > > > > > - * > > > > > > - * - Unsuccessful faults (e.g. when the address wasn't valid). That > > > > > > - * includes arch_vma_access_permitted() failing before reaching here. > > > > > > - * So this is not a "this many hardware page faults" counter. We > > > > > > - * should use the hw profiling for that. > > > > > > - * > > > > > > - * - Incomplete faults (VM_FAULT_RETRY). They will only be counted > > > > > > - * once they're completed. > > > > > > + * Do not account for incomplete faults (VM_FAULT_RETRY). They will be > > > > > > + * counted upon completion. > > > > > > */ > > > > > > - if (ret & (VM_FAULT_ERROR | VM_FAULT_RETRY)) > > > > > > + if (ret & VM_FAULT_RETRY) > > > > > > + return; > > > > > > + > > > > > > + /* Register both successful and failed faults in PGFAULT counters. */ > > > > > > + count_vm_event(PGFAULT); > > > > > > + count_memcg_event_mm(mm, PGFAULT); > > > > > > > > > > Is there reason on why vm events accountings need to be explicitly > > > > > different from perf events right below on handling ERROR? > > > > > > > > I think so. ERROR is quite different from RETRY. If we are, for > > > > example, handling a SIGSEGV (perhaps a GC language?) that should be > > > > accounted. If we can't handle a page fault right now, and need to > > > > retry within the kernel, that should not be accounted. > > > > > > IIUC, the question was about the differences in vm vs perf accounting > > > for errors, not the difference between ERROR and RETRY cases. Matthew, > > > are you answering the right question or did I misunderstand your > > > answer? > > > > Maybe I'm misunderstanding what you're proposing. I thought the > > proposal was to make neither ERROR nor RETRY increment the counters, > > but if the proposal is to make ERROR increment the perf counters > > instead, then that's cool with me. > > Oh, I think now I understand your answer. You were not highlighting > the difference between the who but objecting to the proposal of not > counting both ERROR and RETRY. Am I on the same page now? I think so. Let's see your patch and then we can be sure we're talking about the same thing ;-)
