From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: "Maarten Lankhorst" <dev@mblankhorst.nl>,
"Nicolai Hähnle" <Nicolai.Haehnle@amd.com>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
"Ingo Molnar" <mingo@redhat.com>
Subject: Re: [PATCH v2 02/11] locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop
Date: Tue, 6 Dec 2016 19:29:35 +0100 [thread overview]
Message-ID: <20161206182935.GD3107@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <e9d4cf0f-a2c5-e248-c6f9-3d8c447f9d06@redhat.com>
On Tue, Dec 06, 2016 at 11:03:28AM -0500, Waiman Long wrote:
>
> The mutex_spin_on_owner() function was originally marked noinline
> because it could be a major consumer of CPU cycles in a contended lock.
> Having it shown separately in the perf output will help the users have a
> better understanding of what is consuming all the CPU cycles. So I would
> still like to keep it this way.
ah!, I tried to dig through history but couldn't find a reason for it.
>
> If you have concern about additional latency for non-ww_mutex calls, one
> alternative can be:
That's pretty horrific :/
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WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: "Nicolai Hähnle" <nhaehnle@gmail.com>,
linux-kernel@vger.kernel.org,
"Nicolai Hähnle" <Nicolai.Haehnle@amd.com>,
"Ingo Molnar" <mingo@redhat.com>,
"Maarten Lankhorst" <dev@mblankhorst.nl>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Chris Wilson" <chris@chris-wilson.co.uk>,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v2 02/11] locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop
Date: Tue, 6 Dec 2016 19:29:35 +0100 [thread overview]
Message-ID: <20161206182935.GD3107@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <e9d4cf0f-a2c5-e248-c6f9-3d8c447f9d06@redhat.com>
On Tue, Dec 06, 2016 at 11:03:28AM -0500, Waiman Long wrote:
>
> The mutex_spin_on_owner() function was originally marked noinline
> because it could be a major consumer of CPU cycles in a contended lock.
> Having it shown separately in the perf output will help the users have a
> better understanding of what is consuming all the CPU cycles. So I would
> still like to keep it this way.
ah!, I tried to dig through history but couldn't find a reason for it.
>
> If you have concern about additional latency for non-ww_mutex calls, one
> alternative can be:
That's pretty horrific :/
next prev parent reply other threads:[~2016-12-06 18:29 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-01 14:06 [PATCH v2 00/11] locking/ww_mutex: Keep sorted wait list to avoid stampedes Nicolai Hähnle
2016-12-01 14:06 ` [PATCH v2 01/11] drm/vgem: Use ww_mutex_(un)lock even with a NULL context Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-01 14:18 ` Chris Wilson
2016-12-01 14:18 ` Chris Wilson
2016-12-01 15:14 ` Daniel Vetter
2016-12-01 16:24 ` Peter Zijlstra
2016-12-01 16:24 ` Peter Zijlstra
2016-12-01 14:06 ` [PATCH v2 02/11] locking/ww_mutex: Re-check ww->ctx in the inner optimistic spin loop Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-01 14:36 ` Chris Wilson
2016-12-01 14:36 ` Chris Wilson
2016-12-06 15:06 ` Peter Zijlstra
2016-12-06 15:06 ` Peter Zijlstra
2016-12-06 16:03 ` Waiman Long
2016-12-06 18:29 ` Peter Zijlstra [this message]
2016-12-06 18:29 ` Peter Zijlstra
2016-12-06 18:46 ` Waiman Long
2016-12-01 14:06 ` [PATCH v2 03/11] locking/ww_mutex: Extract stamp comparison to __ww_mutex_stamp_after Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-01 14:42 ` Chris Wilson
2016-12-01 14:42 ` Chris Wilson
2016-12-01 14:06 ` [PATCH v2 04/11] locking/ww_mutex: Set use_ww_ctx even when locking without a context Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-06 15:14 ` Peter Zijlstra
2016-12-06 15:14 ` Peter Zijlstra
2016-12-06 15:25 ` Peter Zijlstra
2016-12-06 15:25 ` Peter Zijlstra
2016-12-16 13:17 ` Nicolai Hähnle
2016-12-16 13:17 ` Nicolai Hähnle
2016-12-17 7:53 ` Maarten Lankhorst
2016-12-17 7:53 ` Maarten Lankhorst
2016-12-17 13:49 ` Peter Zijlstra
2016-12-17 13:49 ` Peter Zijlstra
2016-12-01 14:06 ` [PATCH v2 05/11] locking/ww_mutex: Add waiters in stamp order Nicolai Hähnle
2016-12-01 15:59 ` Chris Wilson
2016-12-01 15:59 ` Chris Wilson
2016-12-16 14:21 ` Nicolai Hähnle
2016-12-16 14:21 ` Nicolai Hähnle
2016-12-06 15:36 ` Peter Zijlstra
2016-12-06 15:36 ` Peter Zijlstra
2016-12-16 13:34 ` Nicolai Hähnle
2016-12-16 13:34 ` Nicolai Hähnle
2016-12-06 16:55 ` Peter Zijlstra
2016-12-06 16:55 ` Peter Zijlstra
2016-12-16 14:19 ` Nicolai Hähnle
2016-12-16 14:19 ` Nicolai Hähnle
2016-12-16 14:46 ` Peter Zijlstra
2016-12-16 14:46 ` Peter Zijlstra
2016-12-16 17:15 ` Peter Zijlstra
2016-12-16 17:15 ` Peter Zijlstra
2016-12-16 18:11 ` Nicolai Hähnle
2016-12-16 20:00 ` Peter Zijlstra
2016-12-16 20:00 ` Peter Zijlstra
2016-12-16 22:35 ` Nicolai Hähnle
2016-12-16 17:20 ` Peter Zijlstra
2016-12-16 17:20 ` Peter Zijlstra
2016-12-16 18:12 ` Nicolai Hähnle
2016-12-16 18:12 ` Nicolai Hähnle
2016-12-01 14:06 ` [PATCH v2 06/11] locking/ww_mutex: Notify waiters that have to back off while adding tasks to wait list Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-01 14:06 ` [PATCH v2 07/11] locking/ww_mutex: Wake at most one waiter for back off when acquiring the lock Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-01 14:06 ` [PATCH v2 08/11] locking/ww_mutex: Yield to other waiters from optimistic spin Nicolai Hähnle
2016-12-01 14:06 ` [PATCH v2 09/11] locking/mutex: Initialize mutex_waiter::ww_ctx with poison when debugging Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-01 14:06 ` [PATCH v2 10/11] Documentation/locking/ww_mutex: Update the design document Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
2016-12-01 14:06 ` [PATCH v2 11/11] [rfc] locking/ww_mutex: Always spin optimistically for the first waiter Nicolai Hähnle
2016-12-01 14:06 ` Nicolai Hähnle
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