在 2023/10/19 21:03, David Hildenbrand 写道:
[你通常不会收到来自 david@xxxxxxxxxx 的电子邮件。请访问
https://aka.ms/LearnAboutSenderIdentification，以了解这一点为什么很重要;]
On 18.10.23 03:30, Zhiguo Jiang wrote:
If the dirty folio is not reclaimed in the shrink process, it do
not need to unmap, which can save shrinking time during traversaling
the dirty folio.
Hi,
I really cannot understand what you mean with "the dirty folio unmap
redundantly". No clue what this patch is supposed to tackle by staring
at the patch subject.
This patch is supposed to improve performance. Can you provide some
proof that it does and that we should even care about this change?
Hi，
What I understand is that in the shrink_folio_list() the sources of the file
dirty folio include two ways below:
1. The dirty folio is from the incoming parameter folio_list,
which is the inactive file lru.
2. The dirty folio is from the PTE dirty bit transferred by
the try_to_unmap().
Currently, both sources of dirty pages are determined after unmap
to determine whether they support pageout and recyling.
For the first source of the dirty folio, if the dirty folio does not
support pageout, the dirty folio can skip unmap in advance to reduce
recyling time.
This patch is not well considered.
The v2 new patch will be submitted later, Please help to continue review.
Thanks
Jiang Zhiguo
Signed-off-by: Zhiguo Jiang <justinjiang@xxxxxxxx>
---
mm/vmscan.c | 72 +++++++++++++++++++++++++++--------------------------
1 file changed, 37 insertions(+), 35 deletions(-)
mode change 100644 => 100755 mm/vmscan.c
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 2cc0cb41fb32..cf555cdfcefc
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1261,6 +1261,43 @@ static unsigned int shrink_folio_list(struct
list_head *folio_list,
enum ttu_flags flags = TTU_BATCH_FLUSH;
bool was_swapbacked =
folio_test_swapbacked(folio);
+ 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))) {
+ /*
+ * Immediately reclaim when
written back.
+ * Similar in principle to
folio_deactivate()
+ * except we already have the
folio isolated
+ * and know it's dirty
+ */
+ node_stat_mod_folio(folio,
NR_VMSCAN_IMMEDIATE,
+ nr_pages);
+ folio_set_reclaim(folio);
+
+ goto activate_locked;
+ }
+
+ if (references == FOLIOREF_RECLAIM_CLEAN)
+ goto keep_locked;
+ if (!may_enter_fs(folio, sc->gfp_mask))
+ goto keep_locked;
+ if (!sc->may_writepage)
+ goto keep_locked;
+ }
+
if (folio_test_pmd_mappable(folio))
flags |= TTU_SPLIT_HUGE_PMD;
@@ -1286,41 +1323,6 @@ static unsigned int shrink_folio_list(struct
list_head *folio_list,
mapping = folio_mapping(folio);
if (folio_test_dirty(folio)) {
Can you elaborate why we want to remove below code? It would have made
sense to me to duplicate the code in an early check before unmap, if the
folio is already dirty before checking all PTEs. But why can we remove
that post-unmap code?
--
Cheers,
David / dhildenb
