Re: [PATCH v7 2/7] mm: introduce external memory hinting API

On 3/10/20 11:20 PM, Minchan Kim wrote:

On Thu, Mar 05, 2020 at 07:15:10PM +0100, Vlastimil Babka wrote:

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On 3/2/20 8:36 PM, Minchan Kim wrote:

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There is usecase that System Management Software(SMS) want to give
a memory hint like MADV_[COLD|PAGEEOUT] to other processes and
in the case of Android, it is the ActivityManagerService.

It's similar in spirit to madvise(MADV_WONTNEED), but the information

You mean MADV_DONTNEED?

Mean to DONT_NEED's future version.

What's that exactly?

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required to make the reclaim decision is not known to the app.

This seems to be mixing up the differences between MADV_DONTNEED and
COLD/PAGEOUT and self-imposed vs external memory hints?

Sorry, I don't understand what you want here.

You say that process_madvise(MADV_[COLD|PAGEEOUT]) is similar to
madvise(MADV_WONTNEED) but the difference is that the information
required to make the reclaim decision is not known to the app.

I see two differences. One is madvise vs process_madvise, which is explained by
"reclaim decision is not known to the app."
The other is MADV_WONTNEED vs MADV_[COLD|PAGEEOUT], which is... I'm not sure
until you say what's "DONT_NEED's future version" :D

Anyway I assume this part is from the versions where the new COLD and PAGEOUT
flags were introduced together with external memory hinting API?