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[6/8] blk-iocost: Avoid to call current_hweight_max if iocg->inuse == iocg->active

Message ID 20221017020011.25016-7-shikemeng@huawei.com
State New
Headers
Series A few cleanup and bugfix patches for blk-iocost |

Commit Message

Kemeng Shi Oct. 17, 2022, 2 a.m. UTC 
  The old_hwi is already max hweight_inuse if iocg->inuse == iocg->active.
Remove unnecessary calculation.

Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
---
 block/blk-iocost.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Tejun Heo Oct. 17, 2022, 7:15 p.m. UTC | #1 
On Mon, Oct 17, 2022 at 10:00:09AM +0800, Kemeng Shi wrote:
> The old_hwi is already max hweight_inuse if iocg->inuse == iocg->active.
> Remove unnecessary calculation.
> 
> Signed-off-by: Kemeng Shi <shikemeng@huawei.com>
> ---
>  block/blk-iocost.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-iocost.c b/block/blk-iocost.c
> index 96c1571a8a1d..fa90f471dfdc 100644
> --- a/block/blk-iocost.c
> +++ b/block/blk-iocost.c
> @@ -2299,7 +2299,10 @@ static void ioc_timer_fn(struct timer_list *timer)
>  			 * Determine the donation amount.
>  			 */
>  			current_hweight(iocg, &hwa, &old_hwi);
> -			hwm = current_hweight_max(iocg);
> +			if (iocg->inuse == iocg->active)
> +				hwm = old_hwi;
> +			else
> +				hwm = current_hweight_max(iocg);

I don't think this is correct. The intermediate nodes might be donating.
This also isn't a meaningful optimization given that it's in the cold
periodic timer path. I'd much rather keep the code simpler unless the
performance benfeit can be clearly demonstrated.

Thanks.
diff mbox series

Patch

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 96c1571a8a1d..fa90f471dfdc 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2299,7 +2299,10 @@  static void ioc_timer_fn(struct timer_list *timer)
 			 * Determine the donation amount.
 			 */
 			current_hweight(iocg, &hwa, &old_hwi);
-			hwm = current_hweight_max(iocg);
+			if (iocg->inuse == iocg->active)
+				hwm = old_hwi;
+			else
+				hwm = current_hweight_max(iocg);
 			new_hwi = hweight_after_donation(iocg, old_hwi, hwm,
 							 usage, &now);
 			/*