On 2024/5/23 09:14, Huang, Ying wrote:
Barry Song <21cnbao@xxxxxxxxx> writes:
On Wed, May 22, 2024 at 9:38 PM Baolin Wang
<baolin.wang@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxx>
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxx/
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.
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.
IIUC, "fallback" means you try to do something, but fail, so try
something else as fallback. If so, then we don't need to count
splitting shmem large folio as fallback.
Agree. In additon, IIUC we have never counted splitting shmem large
folio as THP_SWPOUT_FALLBACK before or after this patch.
For example, before commit 5ed890ce5147 ("mm: vmscan: avoid split during
shrink_folio_list()"), if folio_entire_mapcount() == 0, we will split
the THP. But we will not count it as "fallback" because we haven't
tried to swap it out as a whole.
