On Fri, 19 Jun 2020 12:05:13 -0400 Peter Xu <peterx@xxxxxxxxxx> wrote: [...] > @@ -4393,6 +4425,38 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address, > mem_cgroup_oom_synchronize(false); > } > > + if (ret & VM_FAULT_RETRY) > + return ret; I'm wondering if this also needs a check and exit for VM_FAULT_ERROR. In arch code (s390 and all others I briefly checked), the accounting was skipped for VM_FAULT_ERROR case. > + > + /* > + * Do accounting in the common code, to avoid unnecessary > + * architecture differences or duplicated code. > + * > + * We arbitrarily make the rules be: > + * > + * - faults that never even got here (because the address > + * wasn't valid). That includes arch_vma_access_permitted() Missing "do not count" at the end of the first sentence? > + * failing above. > + * > + * So this is expressly not a "this many hardware page > + * faults" counter. Use the hw profiling for that. > + * > + * - incomplete faults (ie RETRY) do not count (see above). > + * They will only count once completed. > + * > + * - the fault counts as a "major" fault when the final > + * successful fault is VM_FAULT_MAJOR, or if it was a > + * retry (which implies that we couldn't handle it > + * immediately previously). > + * > + * - if the fault is done for GUP, regs wil be NULL and wil -> will Regards, Gerald
