On Mon, Jun 15, 2020 at 06:23:02PM -0400, Peter Xu wrote:
> Use the new mm_fault_accounting() helper for page fault accounting.
>
> Avoid doing page fault accounting multiple times if the page fault is retried.
>
> CC: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> CC: Vasily Gorbik <gor@xxxxxxxxxxxxx>
> CC: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> CC: linux-s390@xxxxxxxxxxxxxxx
> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
> ---
> arch/s390/mm/fault.c | 21 +++++----------------
> 1 file changed, 5 insertions(+), 16 deletions(-)
>
> diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
> index dedc28be27ab..8ca207635b59 100644
> --- a/arch/s390/mm/fault.c
> +++ b/arch/s390/mm/fault.c
> @@ -392,7 +392,7 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
> unsigned long trans_exc_code;
> unsigned long address;
> unsigned int flags;
> - vm_fault_t fault;
> + vm_fault_t fault, major = 0;
>
> tsk = current;
> /*
> @@ -428,7 +428,6 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
> }
>
> address = trans_exc_code & __FAIL_ADDR_MASK;
> - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
> flags = FAULT_FLAG_DEFAULT;
> if (user_mode(regs))
> flags |= FAULT_FLAG_USER;
> @@ -480,6 +479,7 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
> * the fault.
> */
> fault = handle_mm_fault(vma, address, flags);
> + major |= fault & VM_FAULT_MAJOR;
> if (fault_signal_pending(fault, regs)) {
> fault = VM_FAULT_SIGNAL;
> if (flags & FAULT_FLAG_RETRY_NOWAIT)
> @@ -489,21 +489,7 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
> if (unlikely(fault & VM_FAULT_ERROR))
> goto out_up;
>
> - /*
> - * Major/minor page fault accounting is only done on the
> - * initial attempt. If we go through a retry, it is extremely
> - * likely that the page will be found in page cache at that point.
> - */
> if (flags & FAULT_FLAG_ALLOW_RETRY) {
> - if (fault & VM_FAULT_MAJOR) {
> - tsk->maj_flt++;
> - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
> - regs, address);
> - } else {
> - tsk->min_flt++;
> - perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
> - regs, address);
> - }
> if (fault & VM_FAULT_RETRY) {
> if (IS_ENABLED(CONFIG_PGSTE) && gmap &&
> (flags & FAULT_FLAG_RETRY_NOWAIT)) {
Seems like the call to mm_fault_accounting() will be missed if
we entered here with FAULT_FLAG_RETRY_NOWAIT flag set, since it
jumps to "out_up"...
> @@ -519,6 +505,9 @@ static inline vm_fault_t do_exception(struct pt_regs *regs, int access)
> goto retry;
> }
> }
> +
> + mm_fault_accounting(tsk, regs, address, major);
> +
> if (IS_ENABLED(CONFIG_PGSTE) && gmap) {
> address = __gmap_link(gmap, current->thread.gmap_addr,
> address);
> --
> 2.26.2
>
