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Message-ID: <b2814a36-4021-b2a4-52db-6ac707d32835@quicinc.com>
Date:   Wed, 27 Jul 2022 15:44:42 +0800
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Subject: Re: [PATCH] mm/page_owner.c: allow page_owner with given
 start_pfn/count
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To:     "Vlastimil Babka (SUSE)" <vbabka@kernel.org>,
        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>
 <ce6f3bcf-fe77-d042-4517-dd09d090b70b@kernel.org>
From:   Kassey Li <quic_yingangl@quicinc.com>
In-Reply-To: <ce6f3bcf-fe77-d042-4517-dd09d090b70b@kernel.org>
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On 7/26/2022 10:03 PM, Vlastimil Babka (SUSE) wrote:
> 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?

lseek is a good idea.
read_page_owner start with below
	pfn = min_low_pfn + *ppos;
so we need to export the min_low_pfn to user then decide the ppos to seek.
(my_cma.base_pfn - min_low_pfn) is the ppos we want to set.

is there concern to export min_low_pfn  ?
or use a mutex lock for my previous debugfs version patch ?

> 
>> 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?
>>
>