linux-kernel - Re: An cma optimization patch is used for cma

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Message-ID: <f5cd9fe6-3b62-eab8-1ff1-d3943d4bb85b@redhat.com>
Date:   Fri, 13 Aug 2021 09:45:02 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Jichao Zou <zoujc@...orola.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "minchan@...nel.org" <minchan@...nel.org>,
        "song.bao.hua@...ilicon.com" <song.bao.hua@...ilicon.com>,
        "hch@....de" <hch@....de>,
        "m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        JianQi Yang <yangj@...orola.com>,
        Yanjune Tian <tianyje@...orola.com>
Subject: Re: An cma optimization patch is used for cma_[alloc|free].

On 13.08.21 09:00, Jichao Zou wrote:
> Pre-allocate CMA memory that configured in device
> tree, this greatly improves the CMA memory
> allocation efficiency, cma_[alloc|free] is less
> than 1ms, old way is took a few ms to tens or
> hundreds ms.
> 

Please send patches as proper emails (man git-format-patch; man 
git-send-email).

What you propose is turning cma reservations into something comparable 
to permanent boottime allocations. From the POV of the buddy, the pages 
are always allocated and cannot be repurposed for e.g., movable 
allocations until *actually* allocated via CMA.

I don't think we want this behavior upstream.

-- 
Thanks,

David / dhildenb