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 19:10:07 -0700 [thread overview]
Message-ID: <20110329191007.04e8376a.akpm@linux-foundation.org> (raw)
In-Reply-To: <1301450041.3981.55.camel@sli10-conroe>
On Wed, 30 Mar 2011 09:54:01 +0800 Shaohua Li <shaohua.li@intel.com> wrote:
> On Wed, 2011-03-30 at 09:41 +0800, Andrew Morton wrote:
> > On Wed, 30 Mar 2011 09:36:40 +0800 Shaohua Li <shaohua.li@intel.com> wrote:
> >
> > > > how is it that this improves things?
> > > Hmm, it actually is:
> > > struct percpu_counter {
> > > spinlock_t lock;
> > > s64 count;
> > > #ifdef CONFIG_HOTPLUG_CPU
> > > struct list_head list; /* All percpu_counters are on a list */
> > > #endif
> > > s32 __percpu *counters;
> > > } __attribute__((__aligned__(1 << (INTERNODE_CACHE_SHIFT))))
> > > so lock and count are in one cache line.
> >
> > ____cacheline_aligned_in_smp would achieve that?
> ____cacheline_aligned_in_smp can't guarantee the cache alignment for
> multiple nodes, because the variable can be updated by multiple
> nodes/cpus.
Confused. If an object is aligned at a mulitple-of-128 address on one
node, it is aligned at a multiple-of-128 address when viewed from other
nodes, surely?
Even if the cache alignment to which you're referring is the internode
cache, can a 34-byte, L1-cache-aligned structure ever span multiple
internode cachelines?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-03-30 2:09 UTC|newest]
Thread overview: 14+ 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 16:55 ` Andi Kleen
2011-03-29 0:54 ` Shaohua Li
2011-03-29 22:24 ` Andrew Morton
2011-03-29 22:38 ` Christoph Lameter
2011-03-30 1:01 ` Shaohua Li
2011-03-30 1:06 ` Andrew Morton
2011-03-30 1:17 ` Shaohua Li
2011-03-30 1:25 ` Andrew Morton
2011-03-30 1:36 ` Shaohua Li
2011-03-30 1:41 ` Andrew Morton
2011-03-30 1:54 ` Shaohua Li
2011-03-30 2:10 ` Andrew Morton [this message]
2011-03-30 2:35 ` Shaohua Li
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110329191007.04e8376a.akpm@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=andi@firstfloor.org \
--cc=hughd@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=riel@redhat.com \
--cc=shaohua.li@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).