linux-kernel - Re: [RFC PATCH V1 0/3] mm/damon: Add CMA minotor support

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Message-ID: <d604d77e-636f-eb6d-0014-087d880de80e@redhat.com>
Date:   Thu, 17 Mar 2022 17:42:08 +0100
From:   David Hildenbrand <david@...hat.com>
To:     xhao@...ux.alibaba.com, sj@...nel.org
Cc:     rongwei.wang@...ux.alibaba.com, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Baolin Wang <baolin.wang@...ux.alibaba.com>
Subject: Re: [RFC PATCH V1 0/3] mm/damon: Add CMA minotor support

On 17.03.22 08:03, Xin Hao wrote:
> Hi David,
> 
> On 3/16/22 11:09 PM, David Hildenbrand wrote:
>> On 15.03.22 17:37, Xin Hao wrote:
>>
>> s/minotor/monitor/
> Thanks,  i will fix it.
>>
>>> The purpose of these patches is to add CMA memory monitoring function.
>>> In some memory tight scenarios, it will be a good choice to release more
>>> memory by monitoring the CMA memory.
>> I'm sorry, but it's hard to figure out what the target use case should
>> be. Who will release CMA memory and how? Who will monitor that? What are
>> the "some memory tight scenarios"? What's the overall design goal?
> I may not be describing exactly what  i mean，My intention is to find out 
> how much of the reserved CMA space is actually used and which is unused,
> For those that are not used, I understand that they can be released by 
> cma_release(). Of course, This is just a little personal thought that I 
> think is helpful for saving memory.

Hm, not quite. We can place movable allocations on cma areas, to be
migrated away once required for allocations via CMA. So just looking at
the pages allocated within a CMA area doesn't really tell you what's
actually going on.

-- 
Thanks,

David / dhildenb