On 21-Jan-25 5:35 AM, Vinay Banakar wrote:
Sorry, the previous patch was unreadable due to damaged whitespace.
Here is the same patch with fixed indentation.
Signed-off-by: Vinay Banakar <vny@xxxxxxxxxx>
---
mm/vmscan.c | 107
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---------------------------------
1 file changed, 74 insertions(+), 33 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index bd489c1af..1bd510622 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1035,6 +1035,7 @@ static unsigned int shrink_folio_list(struct
list_head *folio_list,
struct folio_batch free_folios;
LIST_HEAD(ret_folios);
LIST_HEAD(demote_folios);
+ LIST_HEAD(pageout_list);
unsigned int nr_reclaimed = 0;
unsigned int pgactivate = 0;
bool do_demote_pass;
@@ -1351,39 +1352,9 @@ static unsigned int shrink_folio_list(struct
list_head *folio_list,
if (!sc->may_writepage)
goto keep_locked;
- /*
- * Folio is dirty. Flush the TLB if a writable entry
- * potentially exists to avoid CPU writes after I/O
- * starts and then write it out here.
- */
- try_to_unmap_flush_dirty();
- switch (pageout(folio, mapping, &plug)) {
- case PAGE_KEEP:
- goto keep_locked;
- case PAGE_ACTIVATE:
- goto activate_locked;
- case PAGE_SUCCESS:
- stat->nr_pageout += nr_pages;
-
- if (folio_test_writeback(folio))
- goto keep;
- if (folio_test_dirty(folio))
- goto keep;
-
- /*
- * A synchronous write - probably a ramdisk. Go
- * ahead and try to reclaim the folio.
- */
- if (!folio_trylock(folio))
- goto keep;
- if (folio_test_dirty(folio) ||
- folio_test_writeback(folio))
- goto keep_locked;
- mapping = folio_mapping(folio);
- fallthrough;
- case PAGE_CLEAN:
- ; /* try to free the folio below */
- }
+ /* Add to pageout list for defered bio submissions */
+ list_add(&folio->lru, &pageout_list);
+ continue;
The dirty pages are collected in a list here...
}
/*
@@ -1494,6 +1465,76 @@ static unsigned int shrink_folio_list(struct
list_head *folio_list,
}
/* 'folio_list' is always empty here */
+ if (!list_empty(&pageout_list)) {
+ /*
+ * Batch TLB flushes by flushing once before processing
all dirty pages.
+ * Since we operate on one PMD at a time, this batches
TLB flushes at
+ * PMD granularity rather than per-page, reducing IPIs.
+ */
+ struct address_space *mapping;
+ try_to_unmap_flush_dirty();
and one flush request is issued for the entire list. Where is the PMD
level (512) batching done? Is that implicit elsewhere in the flow?
+
+ while (!list_empty(&pageout_list)) {
+ struct folio *folio = lru_to_folio(&pageout_list);
+ list_del(&folio->lru);
+
+ /* Recheck if page got reactivated */
+ if (folio_test_active(folio) ||
+ (folio_mapped(folio) && folio_test_young(folio)))
+ goto skip_pageout_locked;
+
+ mapping = folio_mapping(folio);
+ pageout_t pageout_res = pageout(folio, mapping, &plug);
+ switch (pageout_res) {
+ case PAGE_KEEP:
+ goto skip_pageout_locked;
+ case PAGE_ACTIVATE:
+ goto skip_pageout_locked;
+ case PAGE_SUCCESS:
+ stat->nr_pageout += folio_nr_pages(folio);
+
+ if (folio_test_writeback(folio) ||
+ folio_test_dirty(folio))
+ goto skip_pageout;
+
+ /*
+ * A synchronous write - probably a ramdisk. Go
+ * ahead and try to reclaim the folio.
+ */
+ if (!folio_trylock(folio))
+ goto skip_pageout;
+ if (folio_test_dirty(folio) ||
+ folio_test_writeback(folio))
+ goto skip_pageout_locked;
+
+ // Try to free the page
+ if (!mapping ||
+ !__remove_mapping(mapping, folio, true,
+ sc->target_mem_cgroup))
+ goto skip_pageout_locked;
+
+ nr_reclaimed += folio_nr_pages(folio);
+ folio_unlock(folio);
+ continue;
+
+ case PAGE_CLEAN:
+ if (!mapping ||
+ !__remove_mapping(mapping, folio, true,
+ sc->target_mem_cgroup))
+ goto skip_pageout_locked;
+
+ nr_reclaimed += folio_nr_pages(folio);
+ folio_unlock(folio);
+ continue;
+ }
+
+skip_pageout_locked:
+ folio_unlock(folio);
+skip_pageout:
+ list_add(&folio->lru, &ret_folios);
+ }
+ }
+
/* Migrate folios selected for demotion */
nr_reclaimed += demote_folio_list(&demote_folios, pgdat);
/* Folios that could not be demoted are still in @demote_folios */
Regards,
Bharata.
