From: dietmar.eggemann@arm•com (Dietmar Eggemann)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 2/7] sched: rework of sched_domain topology definition
Date: Wed, 19 Mar 2014 15:22:39 +0000 [thread overview]
Message-ID: <5329B63F.9090800@arm.com> (raw)
In-Reply-To: <CAKfTPtDF27X_QJAYEdkb3q6HbULeT4N9t+ChDpdWST+15sndOw@mail.gmail.com>
On 19/03/14 13:33, Vincent Guittot wrote:
[...]
>>> Is there a way to check that MC and GMC have to have
>>> SD_SHARE_PKG_RESOURCES set so that this can't happen unnoticed?
>>
>> So from the core codes perspective those names mean less than nothing.
>> Its just a string to carry along for us meat-bags. The string isn't even
>> there when !SCHED_DEBUG.
>>
>> So from this codes POV you told it it had a domain without PKGSHARE,
>> that's fine.
>>
>> That said; yeah the thing isn't the prettiest piece of code. But it has
>> the big advantage of being the one place where we convert topology into
>> behaviour.
>
> We might add a check of the child in sd_init to ensure that the child
> has at least some properties of the current level.
> I mean that if a level has got the SD_SHARE_PKG_RESOURCES flag, its
> child must also have it. The same for SD_SHARE_CPUPOWER and
> SD_ASYM_PACKING.
>
> so we can add something like the below in sd_init
>
> child_flags = SD_SHARE_PKG_RESOURCES | SD_SHARE_CPUPOWER | SD_ASYM_PACKING
> flags = sd->flags & child_flags
> if (sd->child)
> child_flags &= sd->child->flags
> child_flags &= flags
> if (flags != child_flags)
> pr_info("The topology description looks strange \n");
I tried it with my faulty set-up on TC2 and I get the info message for
the GMC level for all CPU's in sd_init.
I had to pass an 'struct sched_domain *child' pointer into sd_init()
from build_sched_domain() because inside sd_init() sd->child is always NULL.
So one of the requirements of this approach is that a child level like
GMC (which could potentially replace its parent level or otherwise is
destroyed itself) has to specify all flags of its parent level (MC)?
What about SD_NUMA in child_flags? SD_ASYM_PACKING is also a little bit
different than SD_SHARE_PKG_RESOURCES or SD_SHARE_CPUPOWER because it's
not used in the if ... else statement.
But I'm afraid this only works for this specific case of the MC/GMC
layer and is not scalable. If sd->child is a level for which you don't
want to potentially destroy itself or its parent, then you would get
false alarms. IMHO, sd_init() has no information for which pair of
adjacent levels it should apply this check and for which not. Do I miss
something here?
-- Dietmar
>
> Vincent
>
next prev parent reply other threads:[~2014-03-19 15:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-18 17:56 [PATCH v2 0/7] rework sched_domain topology description Vincent Guittot
2014-03-18 17:56 ` [PATCH v2 1/7] sched: remove unused SCHED_INIT_NODE Vincent Guittot
2014-03-19 11:07 ` James Hogan
2014-03-18 17:56 ` [PATCH v2 2/7] sched: rework of sched_domain topology definition Vincent Guittot
2014-03-19 6:01 ` Preeti U Murthy
2014-03-19 11:27 ` Dietmar Eggemann
2014-03-19 12:41 ` Peter Zijlstra
2014-03-19 13:33 ` Vincent Guittot
2014-03-19 15:22 ` Dietmar Eggemann [this message]
2014-03-19 16:14 ` Vincent Guittot
2014-03-19 13:46 ` Dietmar Eggemann
2014-03-18 17:56 ` [PATCH v2 3/7] sched: s390: create a dedicated topology table Vincent Guittot
2014-03-18 17:56 ` [PATCH v2 4/7] sched: powerpc: " Vincent Guittot
2014-03-19 6:04 ` Preeti U Murthy
2014-03-18 17:56 ` [PATCH v2 5/7] sched: add a new SD_SHARE_POWERDOMAIN for sched_domain Vincent Guittot
2014-03-19 6:21 ` Preeti U Murthy
2014-03-19 9:52 ` Vincent Guittot
2014-03-19 11:05 ` Preeti U Murthy
2014-03-19 12:26 ` Vincent Guittot
2014-03-19 11:59 ` Peter Zijlstra
2014-03-19 12:28 ` Vincent Guittot
2014-03-19 12:01 ` Peter Zijlstra
2014-03-19 12:29 ` Vincent Guittot
2014-03-18 17:56 ` [PATCH v2 6/7] sched: ARM: create a dedicated scheduler topology table Vincent Guittot
2014-03-18 17:56 ` [PATCH v2 7/7] sched: powerpc: Add SD_SHARE_POWERDOMAIN for SMT level Vincent Guittot
2014-03-19 12:05 ` Peter Zijlstra
2014-03-19 12:30 ` Vincent Guittot
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