The patch titled
Subject: z3fold: extend compaction function
has been added to the -mm tree. Its filename is
z3fold-extend-compaction-function.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/z3fold-extend-compaction-function.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/z3fold-extend-compaction-function.patch
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------------------------------------------------------
From: Vitaly Wool <vitalywool@xxxxxxxxx>
Subject: z3fold: extend compaction function
z3fold_compact_page() currently only handles the situation when there's a
single middle chunk within the z3fold page. However it may be worth it to
move middle chunk closer to either first or last chunk, whichever is
there, if the gap between them is big enough.
This patch adds the relevant code, using BIG_CHUNK_GAP define as a
threshold for middle chunk to be worth moving.
Link: http://lkml.kernel.org/r/20170131214334.c4f3eac9a477af0fa9a22c46@xxxxxxxxx
Signed-off-by: Vitaly Wool <vitalywool@xxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/z3fold.c | 26 +++++++++++++++++++++++++-
1 file changed, 25 insertions(+), 1 deletion(-)
diff -puN mm/z3fold.c~z3fold-extend-compaction-function mm/z3fold.c
--- a/mm/z3fold.c~z3fold-extend-compaction-function
+++ a/mm/z3fold.c
@@ -268,6 +268,7 @@ static inline void *mchunk_memmove(struc
zhdr->middle_chunks << CHUNK_SHIFT);
}
+#define BIG_CHUNK_GAP 3
/* Has to be called with lock held */
static int z3fold_compact_page(struct z3fold_header *zhdr)
{
@@ -286,8 +287,31 @@ static int z3fold_compact_page(struct z3
zhdr->middle_chunks = 0;
zhdr->start_middle = 0;
zhdr->first_num++;
+ return 1;
}
- return 1;
+
+ /*
+ * moving data is expensive, so let's only do that if
+ * there's substantial gain (at least BIG_CHUNK_GAP chunks)
+ */
+ if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
+ zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
+ BIG_CHUNK_GAP) {
+ mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
+ zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
+ return 1;
+ } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
+ TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
+ + zhdr->middle_chunks) >=
+ BIG_CHUNK_GAP) {
+ unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
+ zhdr->middle_chunks;
+ mchunk_memmove(zhdr, new_start);
+ zhdr->start_middle = new_start;
+ return 1;
+ }
+
+ return 0;
}
/**
_
Patches currently in -mm which might be from vitalywool@xxxxxxxxx are
z3fold-make-pages_nr-atomic.patch
z3fold-fix-header-size-related-issues.patch
z3fold-extend-compaction-function.patch
z3fold-use-per-page-spinlock.patch
z3fold-add-kref-refcounting.patch
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