linux-kernel - Re: [PATCH v3] mm/hugetlb: split hugetlb

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Message-ID: <20200717083608.GA8293@willie-the-truck>
Date:   Fri, 17 Jul 2020 09:36:09 +0100
From:   Will Deacon <will@...nel.org>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Roman Gushchin <guro@...com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Catalin Marinas <catalin.marinas@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Cameron <jonathan.cameron@...wei.com>,
        "H.Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        akpm@...ux-foundation.org, Mike Rapoport <rppt@...ux.ibm.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3] mm/hugetlb: split hugetlb_cma in nodes with memory

On Fri, Jul 17, 2020 at 10:32:53AM +0530, Anshuman Khandual wrote:
> 
> 
> On 07/16/2020 11:55 PM, Mike Kravetz wrote:
> >>From 17c8f37afbf42fe7412e6eebb3619c6e0b7e1c3c Mon Sep 17 00:00:00 2001
> > From: Mike Kravetz <mike.kravetz@...cle.com>
> > Date: Tue, 14 Jul 2020 15:54:46 -0700
> > Subject: [PATCH] hugetlb: move cma reservation to code setting up gigantic
> >  hstate
> > 
> > Instead of calling hugetlb_cma_reserve() directly from arch specific
> > code, call from hugetlb_add_hstate when adding a gigantic hstate.
> > hugetlb_add_hstate is either called from arch specific huge page setup,
> > or as the result of hugetlb command line processing.  In either case,
> > this is late enough in the init process that all numa memory information
> > should be initialized.  And, it is early enough to still use early
> > memory allocator.
> 
> This assumes that hugetlb_add_hstate() is called from the arch code at
> the right point in time for the generic HugeTLB to do the required CMA
> reservation which is not ideal. I guess it must have been a reason why
> CMA reservation should always called by the platform code which knows
> the boot sequence timing better.

Ha, except we've moved it around two or three times already in the last
month or so, so I'd say we don't have a clue when to call it in the arch
code.

Will