zsmalloc: micro-optimize zs_object_copy() (495819ea) · Commits · 戴 / test

A micro-optimization. Avoid additional branching and reduce (a bit) registry pressure (f.e. s_off += size; d_off += size; may be calculated twise: first for >= PAGE_SIZE check and later for offset update in "else" clause). scripts/bloat-o-meter shows some improvement add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-10 (-10) function old new delta zs_object_copy 550 540 -10 Signed-off-by:

Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by:

Minchan Kim <minchan@kernel.org> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by:

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

Linus Torvalds <torvalds@linux-foundation.org>

mm/zsmalloc.c

+7 −8

Original line number	Diff line number	Diff line
		@@ -1537,7 +1537,12 @@ static void zs_object_copy(unsigned long src, unsigned long dst,
		if (written == class->size)
		break;

		if (s_off + size >= PAGE_SIZE) {
		s_off += size;
		s_size -= size;
		d_off += size;
		d_size -= size;

		if (s_off >= PAGE_SIZE) {
		kunmap_atomic(d_addr);
		kunmap_atomic(s_addr);
		s_page = get_next_page(s_page);
		@@ -1546,21 +1551,15 @@ static void zs_object_copy(unsigned long src, unsigned long dst,
		d_addr = kmap_atomic(d_page);
		s_size = class->size - written;
		s_off = 0;
		} else {
		s_off += size;
		s_size -= size;
		}

		if (d_off + size >= PAGE_SIZE) {
		if (d_off >= PAGE_SIZE) {
		kunmap_atomic(d_addr);
		d_page = get_next_page(d_page);
		BUG_ON(!d_page);
		d_addr = kmap_atomic(d_page);
		d_size = class->size - written;
		d_off = 0;
		} else {
		d_off += size;
		d_size -= size;
		}
		}

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