linux-kernel - Re: [PATCH v2] mm: allow deferred page init for vmemmap only

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Message-ID: <20180515203830.GK12670@dhcp22.suse.cz>
Date:   Tue, 15 May 2018 22:38:30 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     Steven Sistare <steven.sistare@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>, tglx@...utronix.de,
        Linux Memory Management List <linux-mm@...ck.org>,
        mgorman@...hsingularity.net, mingo@...nel.org,
        peterz@...radead.org, Steven Rostedt <rostedt@...dmis.org>,
        Fengguang Wu <fengguang.wu@...el.com>,
        Dennis Zhou <dennisszhou@...il.com>
Subject: Re: [PATCH v2] mm: allow deferred page init for vmemmap only

On Tue 15-05-18 11:59:25, Pavel Tatashin wrote:
> > This will always be a maze as the early boot tends to be. Sad but true.
> > That is why I am not really convinced we should use a large hammer and
> > disallow deferred page initialization just because UP implementation of
> > pcp does something too early. We should instead rule that one odd case.
> > Your patch simply doesn't rule a large class of potential issues. It
> > just rules out a potentially useful feature for an odd case. See my
> > point?
> 
> Hi Michal,
> 
> OK, I will send an updated patch with disabling deferred pages only whe
> NEED_PER_CPU_KM. Hopefully, we won't see similar issues in other places.

If we do we will probably need to think more about a more systematic
solution.
-- 
Michal Hocko
SUSE Labs