[0/2] some fix of multi-gen lru

Message

Huan Yang Oct. 18, 2023, 8:20 a.m. UTC

For multi-gen lru shrink_inactive trace, here are
some mistake:

First, nr_scanned in evict_folios means all folios
which it touched in `get_nr_to_scan`(so not means nr_taken).
So, we may get some info from trace like this:

```
kswapd0-89    [000]    64.887613: mm_vmscan_lru_shrink_inactive:
nid=0 nr_scanned=64 nr_reclaimed=0 nr_dirty=0 nr_writeback=0
nr_congested=0 nr_immediate=0 nr_activate_anon=0 nr_activate_file=0
nr_ref_keep=0 nr_unmap_fail=0 priority=4
flags=RECLAIM_WB_FILE|RECLAIM_WB_ASYNC
```

Actually, we don't taken too much folios in shrink. This patch
use difference between before sc->nr_scanned and after shrink to
replace nr_taken and pass this to shrink_inactive tracing.

Second, also like above info, we can't get nr_folios going to where,
actually in multi-gen lru shrink, many keep by folio_update_gen when
look around or other promote this folio.


Third, evict_folios don't gather reclaim_stat info after shrink list,
so, dirty\writeback\congested stat will miss, and we can't control
LRUVEC_CONGESTED or reclaim_throttle.

Patch 1 aim to resolve first and second, patch 2 resolve third.

Huan Yang (2):
  tracing: mm: multigen-lru: fix mglru trace
  mm: multi-gen lru: fix stat count

 include/linux/vmstat.h        |  2 ++
 include/trace/events/vmscan.h |  8 ++++-
 mm/vmscan.c                   | 61 ++++++++++++++++++++++++++++++++---
 3 files changed, 65 insertions(+), 6 deletions(-)