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SubjectRe: [PATCH] drivers, vmw_balloon.c: Increment alloc and sleep_alloc only when page allocation succeeds.
On Tue, 18 Oct 2011, Rakib Mullick wrote:

> While doing allocation statistics in vmballoon_reserve_page function,
> alloc and sleep_alloc has been incremented even if allocation fails.
> But,
> b->stats.alloc and b->stats.sleep_alloc supposed to increment only when
> they succeed. This patch makes sure that, alloc and sleep_alloc gets
> incremented when page allocation succeeds.
>

Dmitry could say for sure, but this seems to actually change the
semantics. If the allocations fail, it increments alloc_fail and
sleep_alloc_fail accordingly so you could easily see 10 alloc and 5
alloc_fail. With your patch, it would be 5 alloc and 5 alloc_fail.

I don't know which one is best, but I would opt to stay with the semantics
that alloc and sleep_alloc have already had rather than changing them.

> Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com>
> ---
>
> diff --git a/drivers/misc/vmw_balloon.c b/drivers/misc/vmw_balloon.c
> index 053d36c..d2c25c9 100644
> --- a/drivers/misc/vmw_balloon.c
> +++ b/drivers/misc/vmw_balloon.c
> @@ -414,11 +414,6 @@ static int vmballoon_reserve_page(struct vmballoon *b, bool can_sleep)
> bool locked = false;
>
> do {
> - if (!can_sleep)
> - STATS_INC(b->stats.alloc);
> - else
> - STATS_INC(b->stats.sleep_alloc);
> -
> flags = can_sleep ? VMW_PAGE_ALLOC_CANSLEEP : VMW_PAGE_ALLOC_NOSLEEP;
> page = alloc_page(flags);
> if (!page) {
> @@ -427,6 +422,11 @@ static int vmballoon_reserve_page(struct vmballoon *b, bool can_sleep)
> else
> STATS_INC(b->stats.sleep_alloc_fail);
> return -ENOMEM;
> + } else {
> + if (!can_sleep)
> + STATS_INC(b->stats.alloc);
> + else
> + STATS_INC(b->stats.sleep_alloc);
> }
>
> /* inform monitor */


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