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Date:   Tue, 26 Jul 2022 16:03:47 +0200
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Subject: Re: [PATCH] mm/page_owner.c: allow page_owner with given
 start_pfn/count
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To:     Kassey Li <quic_yingangl@quicinc.com>,
        Matthew Wilcox <willy@infradead.org>
Cc:     akpm@linux-foundation.org, minchan@kernel.org,
        iamjoonsoo.kim@lge.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, quic_guptap@quicinc.com
References: <20220722150810.27740-1-quic_yingangl@quicinc.com>
 <YtrEXB6o+VROImdg@casper.infradead.org>
 <e518246c-4ffa-14af-e568-798572f75bee@quicinc.com>
From:   "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
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On 7/25/22 10:39, Kassey Li wrote:
> hi, Matthew:
>     sorry for the delay, I just started to learn how to upstream patch, and
> setup my Thunderbird with plain text only.
>     you are right, two users will cause problem here.
>     the uses case is dump CMA area to understand the page usage in a given
> cma pool. 2nd, dump whole memory page owner is very time cost, mostly our
> android device has 8G memory now.
>     I will research and check again, if you have more idea on this , please
> kindly to share.

You could try employing lseek() to specify the start pfn, and as for end
pfn, the process can just stop reading and close when it has seen enough?

> BR
> Kassey
> 
> On 7/22/2022 11:38 PM, Matthew Wilcox wrote:
>> On Fri, Jul 22, 2022 at 11:08:10PM +0800, Kassey Li wrote:
>>> by default, page_owner iterates all page from min_low_pfn to
>>> max_pfn, this cost too much time if we want an alternative pfn range.
>>>
>>> with this patch it allows user to set pfn range to dump the page_onwer.
>>
>> This is a really bad UI.  If two users try to do different ranges at the
>> same time, it'll go wrong.  What use cases are you actually trying to
>> solve?
>