Message-ID: <4FEDCB7A.1060007@redhat.com>
Date: Fri, 29 Jun 2012 11:36:26 -0400
From: Rik van Riel <riel@redhat.com>
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To: Andrea Arcangeli <aarcange@redhat.com>
CC: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Hillf Danton <dhillf@gmail.com>, Dan Smith <danms@us.ibm.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
        Paul Turner <pjt@google.com>,
        Suresh Siddha <suresh.b.siddha@intel.com>,
        Mike Galbraith <efault@gmx.de>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Lai Jiangshan <laijs@cn.fujitsu.com>,
        Bharata B Rao <bharata.rao@gmail.com>,
        Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        Christoph Lameter <cl@linux.com>, Alex Shi <alex.shi@intel.com>,
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        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Don Morris <don.morris@hp.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH 09/40] autonuma: introduce kthread_bind_node()
References: <1340888180-15355-1-git-send-email-aarcange@redhat.com> <1340888180-15355-10-git-send-email-aarcange@redhat.com>
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On 06/28/2012 08:55 AM, Andrea Arcangeli wrote:

> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1792,7 +1792,7 @@ extern void thread_group_times(struct task_struct *p, cputime_t *ut, cputime_t *
>   #define PF_SWAPWRITE	0x00800000	/* Allowed to write to swap */
>   #define PF_SPREAD_PAGE	0x01000000	/* Spread page cache over cpuset */
>   #define PF_SPREAD_SLAB	0x02000000	/* Spread some slab caches over cpuset */
> -#define PF_THREAD_BOUND	0x04000000	/* Thread bound to specific cpu */
> +#define PF_THREAD_BOUND	0x04000000	/* Thread bound to specific cpus */
>   #define PF_MCE_EARLY    0x08000000      /* Early kill for mce process policy */
>   #define PF_MEMPOLICY	0x10000000	/* Non-default NUMA mempolicy */
>   #define PF_MUTEX_TESTER	0x20000000	/* Thread belongs to the rt mutex tester */

Changing the semantics of PF_THREAD_BOUND without so much as
a comment in your changelog or buy-in from the scheduler
maintainers is a big no-no.

Is there any reason you even need PF_THREAD_BOUND in your
kernel numa threads?

I do not see much at all in the scheduler code that uses
PF_THREAD_BOUND and it is not clear at all that your
numa threads get any benefit from them...

Why do you think you need it?

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