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Date: Wed, 14 Jun 2017 08:30:38 +0200 From: Michal Hocko <mhocko@...nel.org> To: Wei Yang <richard.weiyang@...il.com> Cc: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [RESEND PATCH] base/memory: pass the base_section in add_memory_block On Wed 14-06-17 14:05:58, Wei Yang wrote: > Hi, Michael > > I copied your reply here: > > >[Sorry for a late response] > > > >On Wed 07-06-17 16:52:12, Wei Yang wrote: > >> The second parameter of init_memory_block() is used to calculate the > >> start_section_nr of this block, which means any section in the same block > >> would get the same start_section_nr. > > > >Could you be more specific what is the problem here? > > > > There is no problem in this code. I just find a unnecessary calculation and > remove it in this patch. This code needs a larger rething rather than here and there small changes I believe. > >> This patch passes the base_section to init_memory_block(), so that to > >> reduce a local variable and a check in every loop. > > > >But then you are not handling a memblock which starts with a !present > >section. The code is quite hairy but I do not see why your change is any > > I don't see the situation you pointed here. > > In add_memory_block(), section_nr is used to record the first section which is > present. And this variable is used to calculate the section which is passed to > init_memory_block(). > > In init_memory_block(), the section got from add_memory_block(), is used to > calculate scn_nr, but finally transformed to "start_section_nr". That means in > init_memory_block(), we just need the "start_section_nr" of a memory_block. We > don't care about who is the first present section. You are right. The code is confusing as hell! That being said, I am not opposing the patch but I would much rather appreciate a consistent cleanup in the whole memblock vs. sections area. That would be a larger project but the end result is really worth it. -- Michal Hocko SUSE Labs
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