From: Ingo Molnar <mingo@elte.hu>
To: Tejun Heo <tj@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] x86,mm,64bit: Round up memory boundary for init_memory_mapping_high()
Date: Sun, 27 Feb 2011 12:53:50 +0100 [thread overview]
Message-ID: <20110227115350.GB16453@elte.hu> (raw)
In-Reply-To: <20110226085737.GT24828@htj.dyndns.org>
* Tejun Heo <tj@kernel.org> wrote:
> > will have problem with cross node conf. like 0-4g, 8-12g on node0, 4g-8g,
> > 12g-16g on node1.
>
> And how common are they? This whole cruft is basically meaningless if 1GiB
> mapping is supported, IOW, basically on all AMD 64s and all post-nehalem intels.
> Why not just cite the limitation in the comment and stick to something simple?
Such complexity should be justified via very careful "perf stat --repeat"
measurements.
I.e. showing 'before patch' and 'after patch' instruction, TLB miss and cycle
counts, showing that a positive effect that goes beyond the noise of the measurement
exists.
1GB mappings should be assumed as the common case - anything else probably does not
matter from a future performance/scalability POV. For vmalloc() it might make sense
- but even for those precise measurements should be done about the positive effect.
Thanks,
Ingo
next prev parent reply other threads:[~2011-02-27 11:54 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-23 17:19 questions about init_memory_mapping_high() Tejun Heo
2011-02-23 20:24 ` Yinghai Lu
2011-02-23 20:46 ` Tejun Heo
2011-02-23 20:51 ` Yinghai Lu
2011-02-23 21:03 ` Tejun Heo
2011-02-23 22:17 ` Yinghai Lu
2011-02-24 9:15 ` Tejun Heo
2011-02-25 1:37 ` Yinghai Lu
2011-02-25 1:38 ` [PATCH 1/2] x86,mm: Introduce init_memory_mapping_ext() Yinghai Lu
2011-02-25 6:20 ` [PATCH 2/2] x86,mm,64bit: Round up memory boundary for init_memory_mapping_high() Yinghai Lu
2011-02-25 10:03 ` Ingo Molnar
2011-02-25 20:22 ` Yinghai Lu
2011-02-26 3:06 ` [PATCH 1/3] x86, mm: Introduce global page_size_mask Yinghai Lu
2011-02-26 3:07 ` [PATCH 2/3] x86,mm: Introduce init_memory_mapping_ext() Yinghai Lu
2011-02-26 3:08 ` [PATCH 3/3] x86,mm,64bit: Round up memory boundary for init_memory_mapping_high() Yinghai Lu
2011-02-26 10:36 ` Tejun Heo
2011-02-26 10:55 ` Tejun Heo
2011-02-25 11:16 ` [PATCH 2/2] " Tejun Heo
2011-02-25 20:18 ` Yinghai Lu
2011-02-26 8:57 ` Tejun Heo
2011-02-27 11:53 ` Ingo Molnar [this message]
2011-02-28 18:14 ` questions about init_memory_mapping_high() H. Peter Anvin
2011-03-01 8:29 ` Tejun Heo
2011-03-01 19:44 ` H. Peter Anvin
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