From: Michal Hocko <mhocko@kernel.org>
To: Tejun Heo <tj@kernel.org>
Cc: akpm@linux-foundation.org, hannes@cmpxchg.org,
cgroups@vger.kernel.org, linux-mm@kvack.org,
vdavydov@parallels.com, kernel-team@fb.com
Subject: Re: [PATCH 3/3] memcg: drop unnecessary cold-path tests from __memcg_kmem_bypass()
Date: Mon, 14 Sep 2015 21:40:42 +0200 [thread overview]
Message-ID: <20150914194042.GB26273@dhcp22.suse.cz> (raw)
In-Reply-To: <20150913201509.GE25369@htj.duckdns.org>
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@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> 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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WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org,
hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
vdavydov-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org,
kernel-team-b10kYP2dOMg@public.gmane.org
Subject: Re: [PATCH 3/3] memcg: drop unnecessary cold-path tests from __memcg_kmem_bypass()
Date: Mon, 14 Sep 2015 21:40:42 +0200 [thread overview]
Message-ID: <20150914194042.GB26273@dhcp22.suse.cz> (raw)
In-Reply-To: <20150913201509.GE25369-piEFEHQLUPpN0TnZuCh8vA@public.gmane.org>
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-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Acked-by: Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>
> ---
> 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
next prev parent reply other threads:[~2015-09-14 19:40 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-13 20:14 [PATCH 1/3] memcg: collect kmem bypass conditions into __memcg_kmem_bypass() Tejun Heo
2015-09-13 20:14 ` [PATCH 2/3] memcg: ratify and consolidate over-charge handling Tejun Heo
2015-09-13 20:14 ` Tejun Heo
2015-09-13 20:15 ` [PATCH 3/3] memcg: drop unnecessary cold-path tests from __memcg_kmem_bypass() Tejun Heo
2015-09-13 20:15 ` Tejun Heo
2015-09-14 12:51 ` Vladimir Davydov
2015-09-14 12:51 ` Vladimir Davydov
2015-09-14 19:40 ` Michal Hocko [this message]
2015-09-14 19:40 ` Michal Hocko
2015-09-14 12:44 ` [PATCH 2/3] memcg: ratify and consolidate over-charge handling Vladimir Davydov
2015-09-14 12:44 ` Vladimir Davydov
2015-09-14 15:51 ` Tejun Heo
2015-09-14 15:51 ` Tejun Heo
2015-09-14 19:32 ` Michal Hocko
2015-09-14 19:56 ` Tejun Heo
2015-09-14 19:56 ` Tejun Heo
2015-09-15 8:01 ` Michal Hocko
2015-09-15 15:50 ` Tejun Heo
2015-09-14 20:07 ` [PATCH v2 " Tejun Heo
2015-09-15 16:18 ` Johannes Weiner
2015-09-15 16:18 ` Johannes Weiner
2015-09-14 9:03 ` [PATCH 1/3] memcg: collect kmem bypass conditions into __memcg_kmem_bypass() Vladimir Davydov
2015-09-14 9:03 ` Vladimir Davydov
2015-09-14 15:21 ` Michal Hocko
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