From: Andrew Morton <akpm@linux-foundation.org>
To: Shaohua Li <shaohua.li@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>, linux-mm <linux-mm@kvack.org>,
lkml <linux-kernel@vger.kernel.org>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH]mmap: add alignment for some variables
Date: Tue, 29 Mar 2011 18:06:11 -0700 [thread overview]
Message-ID: <20110329180611.a71fe829.akpm@linux-foundation.org> (raw)
In-Reply-To: <1301446882.3981.33.camel@sli10-conroe>
On Wed, 30 Mar 2011 09:01:22 +0800 Shaohua Li <shaohua.li@intel.com> wrote:
> +/*
> + * Make sure vm_committed_as in one cacheline and not cacheline shared with
> + * other variables. It can be updated by several CPUs frequently.
> + */
> +struct percpu_counter vm_committed_as ____cacheline_internodealigned_in_smp;
The mystery deepens. The only cross-cpu writeable fields in there are
percpu_counter.lock and its companion percpu_counter.count. If CPUs
are contending for the lock then that itself is a problem - how does
adding some padding to the struct help anything?
WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Shaohua Li <shaohua.li@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>, linux-mm <linux-mm@kvack.org>,
lkml <linux-kernel@vger.kernel.org>,
Rik van Riel <riel@redhat.com>, Hugh Dickins <hughd@google.com>
Subject: Re: [PATCH]mmap: add alignment for some variables
Date: Tue, 29 Mar 2011 18:06:11 -0700 [thread overview]
Message-ID: <20110329180611.a71fe829.akpm@linux-foundation.org> (raw)
In-Reply-To: <1301446882.3981.33.camel@sli10-conroe>
On Wed, 30 Mar 2011 09:01:22 +0800 Shaohua Li <shaohua.li@intel.com> wrote:
> +/*
> + * Make sure vm_committed_as in one cacheline and not cacheline shared with
> + * other variables. It can be updated by several CPUs frequently.
> + */
> +struct percpu_counter vm_committed_as ____cacheline_internodealigned_in_smp;
The mystery deepens. The only cross-cpu writeable fields in there are
percpu_counter.lock and its companion percpu_counter.count. If CPUs
are contending for the lock then that itself is a problem - how does
adding some padding to the struct help anything?
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next prev parent reply other threads:[~2011-03-30 1:05 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-28 1:58 [PATCH]mmap: add alignment for some variables Shaohua Li
2011-03-28 1:58 ` Shaohua Li
2011-03-28 16:55 ` Andi Kleen
2011-03-28 16:55 ` Andi Kleen
2011-03-29 0:54 ` Shaohua Li
2011-03-29 0:54 ` Shaohua Li
2011-03-29 22:24 ` Andrew Morton
2011-03-29 22:24 ` Andrew Morton
2011-03-29 22:38 ` Christoph Lameter
2011-03-29 22:38 ` Christoph Lameter
2011-03-30 1:01 ` Shaohua Li
2011-03-30 1:01 ` Shaohua Li
2011-03-30 1:06 ` Andrew Morton [this message]
2011-03-30 1:06 ` Andrew Morton
2011-03-30 1:17 ` Shaohua Li
2011-03-30 1:17 ` Shaohua Li
2011-03-30 1:25 ` Andrew Morton
2011-03-30 1:25 ` Andrew Morton
2011-03-30 1:36 ` Shaohua Li
2011-03-30 1:36 ` Shaohua Li
2011-03-30 1:41 ` Andrew Morton
2011-03-30 1:41 ` Andrew Morton
2011-03-30 1:54 ` Shaohua Li
2011-03-30 1:54 ` Shaohua Li
2011-03-30 2:10 ` Andrew Morton
2011-03-30 2:10 ` Andrew Morton
2011-03-30 2:35 ` Shaohua Li
2011-03-30 2:35 ` Shaohua Li
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