* [PATCH] mm/zsmalloc: strength reduce zspage_size calculation
@ 2018-02-26 12:21 Joey Pabalinas
2018-02-28 0:03 ` Minchan Kim
0 siblings, 1 reply; 3+ messages in thread
From: Joey Pabalinas @ 2018-02-26 12:21 UTC (permalink / raw)
To: linux-mm; +Cc: Minchan Kim, Nitin Gupta, linux-kernel, Joey Pabalinas
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Replace the repeated multiplication in the main loop
body calculation of zspage_size with an equivalent
(and cheaper) addition operation.
Signed-off-by: Joey Pabalinas <joeypabalinas@gmail.com>
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index c3013505c30527dc42..647a1a2728634b5194 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -821,15 +821,15 @@ static enum fullness_group fix_fullness_group(struct size_class *class,
*/
static int get_pages_per_zspage(int class_size)
{
+ int zspage_size = 0;
int i, max_usedpc = 0;
/* zspage order which gives maximum used size per KB */
int max_usedpc_order = 1;
for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
- int zspage_size;
int waste, usedpc;
- zspage_size = i * PAGE_SIZE;
+ zspage_size += PAGE_SIZE;
waste = zspage_size % class_size;
usedpc = (zspage_size - waste) * 100 / zspage_size;
--
2.16.2
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/zsmalloc: strength reduce zspage_size calculation
2018-02-26 12:21 [PATCH] mm/zsmalloc: strength reduce zspage_size calculation Joey Pabalinas
@ 2018-02-28 0:03 ` Minchan Kim
2018-02-28 1:26 ` Joey Pabalinas
0 siblings, 1 reply; 3+ messages in thread
From: Minchan Kim @ 2018-02-28 0:03 UTC (permalink / raw)
To: Joey Pabalinas; +Cc: linux-mm, Nitin Gupta, linux-kernel
Hi Joey,
On Mon, Feb 26, 2018 at 02:21:26AM -1000, Joey Pabalinas wrote:
> Replace the repeated multiplication in the main loop
> body calculation of zspage_size with an equivalent
> (and cheaper) addition operation.
>
> Signed-off-by: Joey Pabalinas <joeypabalinas@gmail.com>
>
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index c3013505c30527dc42..647a1a2728634b5194 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -821,15 +821,15 @@ static enum fullness_group fix_fullness_group(struct size_class *class,
> */
> static int get_pages_per_zspage(int class_size)
> {
> + int zspage_size = 0;
> int i, max_usedpc = 0;
> /* zspage order which gives maximum used size per KB */
> int max_usedpc_order = 1;
>
> for (i = 1; i <= ZS_MAX_PAGES_PER_ZSPAGE; i++) {
> - int zspage_size;
> int waste, usedpc;
>
> - zspage_size = i * PAGE_SIZE;
> + zspage_size += PAGE_SIZE;
> waste = zspage_size % class_size;
> usedpc = (zspage_size - waste) * 100 / zspage_size;
>
Thanks for the patch! However, it's used only zs_create_pool which
is really cold path so I don't feel it would improve for real practice.
Thanks.
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm/zsmalloc: strength reduce zspage_size calculation
2018-02-28 0:03 ` Minchan Kim
@ 2018-02-28 1:26 ` Joey Pabalinas
0 siblings, 0 replies; 3+ messages in thread
From: Joey Pabalinas @ 2018-02-28 1:26 UTC (permalink / raw)
To: Minchan Kim; +Cc: linux-mm, Nitin Gupta, linux-kernel
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On Wed, Feb 28, 2018 at 09:03:19AM +0900, Minchan Kim wrote:
> Thanks for the patch! However, it's used only zs_create_pool which
> is really cold path so I don't feel it would improve for real practice.
Very true; in retrospect this this definitely isn't a very hot path at
all, haha. Cheers :)
--
Joey Pabalinas
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2018-02-26 12:21 [PATCH] mm/zsmalloc: strength reduce zspage_size calculation Joey Pabalinas
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