On Sun 13-09-15 16:15:09, Tejun Heo wrote:
> __memcg_kmem_bypass() decides whether a kmem allocation should be
> bypassed to the root memcg. Some conditions that it tests are valid
> criteria regarding who should be held accountable; however, there are
> a couple unnecessary tests for cold paths - __GFP_FAIL and
> fatal_signal_pending().
>
> The previous patch updated try_charge() to handle both __GFP_FAIL and
> dying tasks correctly and the only thing these two tests are doing is
> making accounting less accurate and sprinkling tests for cold path
> conditions in the hot paths. There's nothing meaningful gained by
> these extra tests.
>
> This patch removes the two unnecessary tests from
> __memcg_kmem_bypass().
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> include/linux/memcontrol.h | 14 --------------
> 1 file changed, 14 deletions(-)
>
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -780,24 +780,10 @@ static inline bool __memcg_kmem_bypass(g
> {
> if (!memcg_kmem_enabled())
> return true;
> -
> if (gfp & __GFP_NOACCOUNT)
> return true;
> - /*
> - * __GFP_NOFAIL allocations will move on even if charging is not
> - * possible. Therefore we don't even try, and have this allocation
> - * unaccounted. We could in theory charge it forcibly, but we hope
> - * those allocations are rare, and won't be worth the trouble.
> - */
> - if (gfp & __GFP_NOFAIL)
> - return true;
> if (in_interrupt() || (!current->mm) || (current->flags & PF_KTHREAD))
> return true;
> -
> - /* If the test is dying, just let it go. */
> - if (unlikely(fatal_signal_pending(current)))
> - return true;
> -
> return false;
> }
>
--
Michal Hocko
SUSE Labs
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