linux-kernel - Re: [PATCH v2 RFC/RFT 0/5] Save single pages from CMA area

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Date:   Wed, 27 Mar 2019 09:08:21 +0100
From:   Christoph Hellwig <hch@....de>
To:     Nicolin Chen <nicoleotsuka@...il.com>
Cc:     hch@....de, robin.murphy@....com, vdumpa@...dia.com,
        linux@...linux.org.uk, catalin.marinas@....com,
        will.deacon@....com, joro@...tes.org, m.szyprowski@...sung.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        iommu@...ts.linux-foundation.org, tony@...mide.com
Subject: Re: [PATCH v2 RFC/RFT 0/5] Save single pages from CMA area

On Tue, Mar 26, 2019 at 04:01:26PM -0700, Nicolin Chen wrote:
> This series of patches try to save single pages from CMA area bypassing
> all CMA single page alloctions and allocating normal pages instead, as
> all addresses within one single page are contiguous.
> 
> We had once applied the PATCH-5 but reverted it as actually not all the
> callers handled the fallback allocations. Per Robin's suggestion, let's
> stuff alloc_pages()/free_page() fallbacks to those callers before having
> PATCH-5.

Given the problems this has caused so far I'd like to see a good
explanation of why this optimization is so important that all the churn
is even worth it..