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Commit 495819ea authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Linus Torvalds
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zsmalloc: micro-optimize zs_object_copy() 



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: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1ec7cfb1

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;

		}

	}