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.
