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Date: Mon, 6 Mar 2017 14:42:25 -0500 From: Tejun Heo <tj@...nel.org> To: Wei Yang <richard.weiyang@...il.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org, linux-kernel@...r.kernel.org Subject: Re: [RFC PATCH 2/2] mm/sparse: add last_section_nr in sparse_init() to reduce some iteration cycle Hello, Wei. On Fri, Feb 17, 2017 at 10:12:31PM +0800, Wei Yang wrote: > > And compare the ruling with the iteration for the loop to be (1UL << > > 5) and (1UL << 19). > > The runtime is 0.00s and 0.04s respectively. The absolute value is not much. systemd-analyze usually does a pretty good job of breaking down which phase took how long. It might be worthwhile to test whether the improvement is actually visible during the boot. > >> * Do we really need to add full reverse iterator to just get the > >> highest section number? > >> > > > > You are right. After I sent out the mail, I realized just highest pfn > > is necessary. That said, getting efficient is always great as long as the added complexity is justifiably small enough. If you can make the change simple enough, it'd be a lot easier to merge. Thanks. -- tejun
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