From: Andi Kleen <andi@firstfloor.org>
To: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <js1304@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
andi@firstfloor.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH] mm: introduce numa_zero_pfn
Date: Wed, 12 Dec 2012 21:15:29 +0100 [thread overview]
Message-ID: <20121212201529.GD16230@one.firstfloor.org> (raw)
In-Reply-To: <0000013b90beeb93-87f65a09-0cc3-419f-be26-5271148cb947-000000@email.amazonses.com>
> I would expect a processor to fetch the zero page cachelines from the l3
> cache from other sockets avoiding memory transactions altogether. The zero
> page is likely in use somewhere so no typically no memory accesses should
> occur in a system.
It depends on how effectively the workload uses the caches. If something
is a cache pig of the L3 cache, then even shareable cache lines may need
to be refetched regularly.
But if your workloads spends a significant part of its time reading
from zero page read only data there is something wrong with the workload.
I would do some data profiling first to really prove that is the case.
-Andi
--
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/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
WARNING: multiple messages have this Message-ID (diff)
From: Andi Kleen <andi@firstfloor.org>
To: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <js1304@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
andi@firstfloor.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH] mm: introduce numa_zero_pfn
Date: Wed, 12 Dec 2012 21:15:29 +0100 [thread overview]
Message-ID: <20121212201529.GD16230@one.firstfloor.org> (raw)
In-Reply-To: <0000013b90beeb93-87f65a09-0cc3-419f-be26-5271148cb947-000000@email.amazonses.com>
> I would expect a processor to fetch the zero page cachelines from the l3
> cache from other sockets avoiding memory transactions altogether. The zero
> page is likely in use somewhere so no typically no memory accesses should
> occur in a system.
It depends on how effectively the workload uses the caches. If something
is a cache pig of the L3 cache, then even shareable cache lines may need
to be refetched regularly.
But if your workloads spends a significant part of its time reading
from zero page read only data there is something wrong with the workload.
I would do some data profiling first to really prove that is the case.
-Andi
next prev parent reply other threads:[~2012-12-12 20:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-12 17:03 [PATCH] mm: introduce numa_zero_pfn Joonsoo Kim
2012-12-12 17:03 ` Joonsoo Kim
2012-12-12 18:09 ` Kirill A. Shutemov
2012-12-12 20:12 ` Christoph Lameter
2012-12-12 20:12 ` Christoph Lameter
2012-12-12 20:15 ` Andi Kleen [this message]
2012-12-12 20:15 ` Andi Kleen
2012-12-17 13:58 ` JoonSoo Kim
2012-12-17 13:58 ` JoonSoo Kim
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=20121212201529.GD16230@one.firstfloor.org \
--to=andi@firstfloor.org \
--cc=akpm@linux-foundation.org \
--cc=cl@linux.com \
--cc=js1304@gmail.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.