linux-kernel - Re: [RFC PATCH v4 0/5] DAMON based tiered memory management for CXL memory

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Date: Wed, 15 May 2024 09:18:35 -0700
From: SeongJae Park <sj@...nel.org>
To: Honggyu Kim <honggyu.kim@...com>
Cc: SeongJae Park <sj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	damon@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	linux-trace-kernel@...r.kernel.org,
	Hyeongtak Ji <hyeongtak.ji@...com>,
	Rakie Kim <rakie.kim@...com>,
	kernel_team@...ynix.com
Subject: Re: [RFC PATCH v4 0/5] DAMON based tiered memory management for CXL memory

Hi Honggyu,

On Mon, 13 May 2024 20:59:15 +0900 Honggyu Kim <honggyu.kim@...com> wrote:

> Hi SeongJae,
> 
> Thanks very much for your work!  It got delayed due to the priority
> changes in my workplace for building another heterogeneous memory
> allocator.
> https://github.com/skhynix/hmsdk/wiki/hmalloc

No problem at all.  We all work on our own schedule and nobody can chase/push
anybody :)

> 
> On Sun, 12 May 2024 10:54:42 -0700 SeongJae Park <sj@...nel.org> wrote:
> > There was an RFC IDEA "DAMOS-based Tiered-Memory Management" previously
> > posted at [1].
> > 
> > It says there is no implementation of the demote/promote DAMOS action
> > are made.  This RFC is about its implementation for physical address
> > space.
> > 
> > Changes from RFC v3
> > (https://lore.kernel.org/20240405060858.2818-1-honggyu.kim@sk.com):
> 
> This link cannot be opened.  I will share the link again here.
> https://lore.kernel.org/all/20240405060858.2818-1-honggyu.kim@sk.com

Thank you for checking the link!  It's weird though, since I can open the link
on my Chrome browser.

> 
> >   0. updated from v3 and posted by SJ on behalf of Hunggyu under his
> >      approval.
> >   1. Do not reuse damon_pa_pageout() and drop 'enum migration_mode'
> >   2. Drop vmstat change
> 
> I haven't checked whether I can collect useful information without
> vmstat, but the changes look good in general except for that.

I was thinking you could use DAMOS stat[1] for the schemes and assuming no
reply to it as an agreement, but maybe I should made it clear.  Do you think
DAMOS stat cannot be used instead?  If so, what would be the limitation of
DAMOS stat for your usage?

> 
> >   3. Drop unnecessary page reference check
> 
> I will compare this patch series with my previous v3 patchset and get
> back to you later maybe next week.

Thank you very much!  Unless I get a good enough test setup and results from it
on my own or from others' help, your test result would be the last requirement
for dropping RFC from this patchset.

> Sorry, I will have another break this week.

No problem, I hope you to have nice break.  Nobody can chase/push others.  We
all do this work voluntarily for our own fun and profit, right? ;)


[1] https://lore.kernel.org/damon/20240405060858.2818-1-honggyu.kim@sk.com


Thanks,
SJ

> 
> Thanks,
> Honggyu