Messages in this thread | | | Date | Wed, 22 May 2024 19:24:45 +0800 | Subject | Re: [PATCH] mm: drop the 'anon_' prefix for swap-out mTHP counters | From | Baolin Wang <> |
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On 2024/5/22 18:40, Barry Song wrote: > On Wed, May 22, 2024 at 9:38 PM Baolin Wang > <baolin.wang@linux.alibaba.com> wrote: >> >> >> >> On 2024/5/22 16:58, David Hildenbrand wrote: >>> On 22.05.24 10:51, Baolin Wang wrote: >>>> The mTHP swap related counters: 'anon_swpout' and >>>> 'anon_swpout_fallback' are >>>> confusing with an 'anon_' prefix, since the shmem can swap out >>>> non-anonymous >>>> pages. So drop the 'anon_' prefix to keep consistent with the old swap >>>> counter >>>> names. >>>> >>>> Suggested-by: "Huang, Ying" <ying.huang@intel.com> >>>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com> >>>> --- >>> >>> Am I daydreaming or did we add the anon_ for a reason and discussed the >>> interaction with shmem? At least I remember some discussion around that. >> >> Do you mean the shmem mTHP allocation counters in previous >> discussion[1]? But for 'anon_swpout' and 'anon_swpout_fallback', I can >> not find previous discussions that provided a reason for adding the >> ‘anon_’ prefix. Barry, any comments? Thanks. > > HI Baolin, > We had tons of emails discussing about namin and I found this email, > > https://lore.kernel.org/all/bca6d142-15fd-4af5-9f71-821f891e8305@redhat.com/ > > David had this comment, > "I'm wondering if these should be ANON specific for now. We might want to > add others (shmem, file) in the future." > > This is likely how the 'anon_' prefix started being added, although it > wasn't specifically > targeting swapout.
That's what I missed before. Thanks Barry.
> I sense your patch slightly alters the behavior of thp_swpout_fallback > in /proc/vmstat. > Previously, we didn't classify them as THP_SWPOUT_FALLBACK, even though we > always split them.
Sorry I did not get you here. I just re-name the mTHP swpout_fallback, how can this patch change the THP_SWPOUT_FALLBACK statistic counted by count_vm_event()?
> if (folio_test_anon(folio) && folio_test_swapbacked(folio)) { > ... > if (!add_to_swap(folio)) { > int __maybe_unused order = > folio_order(folio); > > if (!folio_test_large(folio)) > goto activate_locked_split; > /* Fallback to swap normal pages */ > if (split_folio_to_list(folio, > folio_list)) > goto activate_locked; > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > if (nr_pages >= HPAGE_PMD_NR) { > count_memcg_folio_events(folio, > THP_SWPOUT_FALLBACK, 1); > > count_vm_event(THP_SWPOUT_FALLBACK); > } > count_mthp_stat(order, > MTHP_STAT_ANON_SWPOUT_FALLBACK); > #endif > if (!add_to_swap(folio)) > goto activate_locked_split; > } > } > } else if (folio_test_swapbacked(folio) && > folio_test_large(folio)) { > /* Split shmem folio */ > if (split_folio_to_list(folio, folio_list)) > goto keep_locked; > } > > > > If the goal is to incorporate pmd-mapped shmem under thp_swpout* in > /proc/vmstat, > and if there is consistency between /proc/vmstat and sys regarding > their definitions, > then I have no objection to this patch.
I think this is the goal, moreover shmem will support large folio (not only THP) in future, so swpout related counters should be defined as clear as possible.
However, shmem_swpout and shmem_swpout_* > appear more intuitive, given that thp_swpout_* in /proc/vmstat has > never shown any > increments for shmem until now - we have been always splitting shmem in vmscan.
This is somewhat similar to our previous discussion on the naming of the shmem's mTHP counter[1], as David suggested, we should keep counter name consistency for now and add more in the future as needed.
[1] https://lore.kernel.org/all/ce6be451-7c5a-402f-8340-be40699829c2@redhat.com/ > > By the way, if this patch is accepted, it must be included in version > 6.10 to maintain > ABI compatibility. Additionally, documentation must be updated accordingly.
Sure. I missed update the documentation, and will do in next version.
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