在 2023/10/19 10:39, Yu Zhao 写道:
On Wed, Oct 18, 2023 at 8:17 PM Huan Yang <link@xxxxxxxx> wrote:
Hi Yu Zhao,
Thanks for your reply.
在 2023/10/19 0:21, Yu Zhao 写道:
On Wed, Oct 18, 2023 at 2:22 AM Huan Yang <link@xxxxxxxx> wrote:
For multi-gen lru reclaim in evict_folios, like shrink_inactive_list,
gather folios which isolate to reclaim, and invoke shirnk_folio_list.
But, when complete shrink, it not gather shrink reclaim stat into sc,
we can't get info like nr_dirty\congested in reclaim, and then
control writeback, dirty number and mark as LRUVEC_CONGESTED, or
just bpf trace shrink and get correct sc stat.
This patch fix this by simple copy code from shrink_inactive_list when
end of shrink list.
MGLRU doesn't try to write back dirt file pages in the reclaim path --
it filters them out in sort_folio() and leaves them to the page
Nice to know this, sort_folio() filters some folio indeed.
But, I want to know, if we touch some folio in shrink_folio_list(), may some
folio become dirty or writeback even if sort_folio() filter then?
Good question: in that case MGLRU still doesn't try to write those
folios back because isolate_folio() cleared PG_reclaim and
shrink_folio_list() checks PG_reclaim:
Thank you too much. So, MGLRU have many diff between typic LRU reclaim.
So, why don't offer MGLRU a own shrink path to avoid so many check of folio?
And more think, it's nice to assign a anon/file reclaim hook into
anon_vma/address_space?
(Each folio, have their own shrink path, don't try check path if it no
need.)
if (folio_test_dirty(folio)) {
/*
* Only kswapd can writeback filesystem folios
* to avoid risk of stack overflow. But avoid
* injecting inefficient single-folio I/O into
* flusher writeback as much as possible: only
* write folios when we've encountered many
* dirty folios, and when we've already scanned
* the rest of the LRU for clean folios and see
* the same dirty folios again (with the reclaim
* flag set).
*/
if (folio_is_file_lru(folio) &&
(!current_is_kswapd() ||
!folio_test_reclaim(folio) ||
!test_bit(PGDAT_DIRTY, &pgdat->flags))) {
Thanks
