On Mon, Feb 17, 2020 at 09:41:40PM -0800, David Rientjes wrote:
> The thp_fault_fallback stat in either /proc/vmstat is incremented if
Nit: ^ "either" here looks wrong
> either the hugepage allocation fails through the page allocator or the
> hugepage charge fails through mem cgroup.
>
> This patch leaves this field untouched but adds a new field,
> thp_fault_fallback_charge, which is incremented only when the mem cgroup
> charge fails.
>
> This distinguishes between faults that want to be backed by hugepages but
> fail due to fragmentation (or low memory conditions) and those that fail
> due to mem cgroup limits. That can be used to determine the impact of
> fragmentation on the system by excluding faults that failed due to memcg
> usage.
>
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
> Documentation/admin-guide/mm/transhuge.rst | 5 +++++
> include/linux/vm_event_item.h | 1 +
> mm/huge_memory.c | 2 ++
> mm/vmstat.c | 1 +
> 4 files changed, 9 insertions(+)
>
> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> --- a/Documentation/admin-guide/mm/transhuge.rst
> +++ b/Documentation/admin-guide/mm/transhuge.rst
> @@ -310,6 +310,11 @@ thp_fault_fallback
> is incremented if a page fault fails to allocate
> a huge page and instead falls back to using small pages.
>
> +thp_fault_fallback_charge
> + is incremented if a page fault fails to charge a huge page and
> + instead falls back to using small pages even through the
^ though
> + allocation was successful.
> +
> thp_collapse_alloc_failed
> is incremented if khugepaged found a range
> of pages that should be collapsed into one huge page but failed
> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
> --- a/include/linux/vm_event_item.h
> +++ b/include/linux/vm_event_item.h
> @@ -73,6 +73,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> THP_FAULT_ALLOC,
> THP_FAULT_FALLBACK,
> + THP_FAULT_FALLBACK_CHARGE,
> THP_COLLAPSE_ALLOC,
> THP_COLLAPSE_ALLOC_FAILED,
> THP_FILE_ALLOC,
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -597,6 +597,7 @@ static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
> if (mem_cgroup_try_charge_delay(page, vma->vm_mm, gfp, &memcg, true)) {
> put_page(page);
> count_vm_event(THP_FAULT_FALLBACK);
> + count_vm_event(THP_FAULT_FALLBACK_CHARGE);
> return VM_FAULT_FALLBACK;
> }
>
> @@ -1406,6 +1407,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
> put_page(page);
> ret |= VM_FAULT_FALLBACK;
> count_vm_event(THP_FAULT_FALLBACK);
> + count_vm_event(THP_FAULT_FALLBACK_CHARGE);
> goto out;
> }
>
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -1254,6 +1254,7 @@ const char * const vmstat_text[] = {
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> "thp_fault_alloc",
> "thp_fault_fallback",
> + "thp_fault_fallback_charge",
> "thp_collapse_alloc",
> "thp_collapse_alloc_failed",
> "thp_file_alloc",
--
Sincerely yours,
Mike.
