From: Andrew Morton <akpm@linux-foundation.org>
To: Michal Hocko <mhocko@suse.cz>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>,
kamezawa.hiroyu@jp.fujitsu.com, minchan@kernel.org,
shangw@linux.vnet.ibm.com, yinghai@kernel.org,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: + mm-memblock-reduce-overhead-in-binary-search.patch added to -mm tree
Date: Mon, 8 Oct 2012 12:42:34 -0700 [thread overview]
Message-ID: <20121008124234.3e8c511b.akpm@linux-foundation.org> (raw)
In-Reply-To: <20120910115514.GC17437@dhcp22.suse.cz>
On Mon, 10 Sep 2012 13:55:15 +0200
Michal Hocko <mhocko@suse.cz> wrote:
> > >OK. Thanks for the clarification. The main question remains, though. Is
> > >this worth for memblock_is_memory?
> >
> > There are many call sites need to call pfn_valid, how can you guarantee all
> > the addrs are between memblock_start_of_DRAM() and memblock_end_of_DRAM(),
> > if not can this reduce possible overhead ?
>
> That was my question. I hoped for an answer in the patch description. I
> am really not familiar with unicore32 which is the only user now.
>
> > I add unlikely which means that this will not happen frequently. :-)
>
> unlikely doesn't help much in this case. You would be doing the test for
> every pfn_valid invocation anyway. So the main question is. Do you want
> to optimize for something that doesn't happen often when it adds a cost
> (not a big one but still) for the more probable cases?
> I would say yes if we clearly see that the exceptional case really pays
> off. Nothing in the changelog convinces me about that.
I don't believe Michal's questions have been resolved yet, so I'll keep
this patch on hold for now.
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next prev parent reply other threads:[~2012-10-08 19:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120907235058.A33F75C0219@hpza9.eem.corp.google.com>
2012-09-10 8:22 ` + mm-memblock-reduce-overhead-in-binary-search.patch added to -mm tree Michal Hocko
2012-09-10 9:46 ` Wanpeng Li
2012-09-10 11:05 ` Michal Hocko
2012-09-10 11:30 ` Wanpeng Li
2012-09-10 11:30 ` Wanpeng Li
2012-09-10 11:55 ` Michal Hocko
2012-10-08 19:42 ` Andrew Morton [this message]
2012-12-18 23:11 ` Andrew Morton
2012-09-10 9:46 ` Wanpeng Li
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