z3fold: extend compaction function (1b096e5a) · Commits · 戴 / test

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@gmail.com Signed-off-by:

Vitaly Wool <vitalywool@gmail.com> Reviewed-by:

Dan Streetman <ddstreet@ieee.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/z3fold.c

+25 −1

Original line number	Diff line number	Diff line
		@@ -268,6 +268,7 @@ static inline void mchunk_memmove(struct z3fold_header zhdr,
		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 z3fold_header *zhdr)
		zhdr->middle_chunks = 0;
		zhdr->start_middle = 0;
		zhdr->first_num++;
		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;
		}

		/**

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