On Wed, Aug 14, 2024 at 6:28 PM Kanchana P Sridhar
<kanchana.p.sridhar@xxxxxxxxx> wrote:
>
> Added count_zswap_thp_swpout_vm_event() that will increment the
> appropriate mTHP/PMD vmstat event counters if zswap_store succeeds for
> a large folio:
>
> zswap_store mTHP order [0, HPAGE_PMD_ORDER-1] will increment these
> vmstat event counters:
>
> ZSWPOUT_4KB_FOLIO
> mTHP_ZSWPOUT_8kB
> mTHP_ZSWPOUT_16kB
> mTHP_ZSWPOUT_32kB
> mTHP_ZSWPOUT_64kB
> mTHP_ZSWPOUT_128kB
> mTHP_ZSWPOUT_256kB
> mTHP_ZSWPOUT_512kB
> mTHP_ZSWPOUT_1024kB
>
> zswap_store of a PMD-size THP, i.e., mTHP order HPAGE_PMD_ORDER, will
> increment both these vmstat event counters:
>
> ZSWPOUT_PMD_THP_FOLIO
> mTHP_ZSWPOUT_2048kB
>
> Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
> ---
> mm/page_io.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> diff --git a/mm/page_io.c b/mm/page_io.c
> index 0a150c240bf4..ab54d2060cc4 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -172,6 +172,49 @@ int generic_swapfile_activate(struct swap_info_struct *sis,
> goto out;
> }
>
> +/*
> + * Count vmstats for ZSWAP store of large folios (mTHP and PMD-size THP).
> + */
> +static inline void count_zswap_thp_swpout_vm_event(struct folio *folio)
> +{
> + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && folio_test_pmd_mappable(folio)) {
> + count_vm_event(ZSWPOUT_PMD_THP_FOLIO);
> + count_vm_event(mTHP_ZSWPOUT_2048kB);
> + } else if (folio_order(folio) == 0) {
> + count_vm_event(ZSWPOUT_4KB_FOLIO);
> + } else if (IS_ENABLED(CONFIG_THP_SWAP)) {
> + switch (folio_order(folio)) {
> + case 1:
> + count_vm_event(mTHP_ZSWPOUT_8kB);
> + break;
> + case 2:
> + count_vm_event(mTHP_ZSWPOUT_16kB);
> + break;
> + case 3:
> + count_vm_event(mTHP_ZSWPOUT_32kB);
> + break;
> + case 4:
> + count_vm_event(mTHP_ZSWPOUT_64kB);
> + break;
> + case 5:
> + count_vm_event(mTHP_ZSWPOUT_128kB);
> + break;
> + case 6:
> + count_vm_event(mTHP_ZSWPOUT_256kB);
> + break;
> + case 7:
> + count_vm_event(mTHP_ZSWPOUT_512kB);
> + break;
> + case 8:
> + count_vm_event(mTHP_ZSWPOUT_1024kB);
> + break;
> + case 9:
> + count_vm_event(mTHP_ZSWPOUT_2048kB);
> + break;
> + }
The number of orders is PMD_ORDER, also ilog2(MAX_PTRS_PER_PTE) .
PMD_ORDER isn't necessarily 9. It seems we need some general way
to handle this and avoid so many duplicated case 1, case 2.... case 9.
> + }
> +}
> +
> /*
> * We may have stale swap cache pages in memory: notice
> * them here and get rid of the unnecessary final write.
> @@ -196,6 +239,7 @@ int swap_writepage(struct page *page, struct writeback_control *wbc)
> return ret;
> }
> if (zswap_store(folio)) {
> + count_zswap_thp_swpout_vm_event(folio);
> folio_start_writeback(folio);
> folio_unlock(folio);
> folio_end_writeback(folio);
> --
> 2.27.0
>
Thanks
Barry
