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UPSTREAM: zsmalloc: micro-optimize zs_object_copy()

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(cherry-pick from commit 495819ead5ad02174208994ca610852a7791a2f2)

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

Bug: 25951511

Change-Id: Ie3255d79246493fc755e6256f12082e692c0fc3c
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>
This commit is contained in:
Sergey Senozhatsky 2015-04-15 16:16:15 -07:00 committed by Srinivasarao P
parent 4c117f8df8
commit f3dbbaaa41
1 changed files with 7 additions and 8 deletions
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15
mm/zsmalloc.c
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@ -1538,7 +1538,12 @@ static void zs_object_copy(unsigned long src, unsigned long dst,
if (written == class->size) if (written == class->size)
break; 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(d_addr);
kunmap_atomic(s_addr); kunmap_atomic(s_addr);
s_page = get_next_page(s_page); s_page = get_next_page(s_page);
@ -1547,21 +1552,15 @@ static void zs_object_copy(unsigned long src, unsigned long dst,
d_addr = kmap_atomic(d_page); d_addr = kmap_atomic(d_page);
s_size = class->size - written; s_size = class->size - written;
s_off = 0; 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); kunmap_atomic(d_addr);
d_page = get_next_page(d_page); d_page = get_next_page(d_page);
BUG_ON(!d_page); BUG_ON(!d_page);
d_addr = kmap_atomic(d_page); d_addr = kmap_atomic(d_page);
d_size = class->size - written; d_size = class->size - written;
d_off = 0; d_off = 0;
} else {
d_off += size;
d_size -= size;
} }
} }