linux-kernel - Re: [RFC PATCH v4 0/9] mm: Hot page tracking and promotion infrastructure

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Message-ID: <aWZZcOFxhniDpuj3@gourry-fedora-PF4VCD3F>
Date: Tue, 13 Jan 2026 09:40:48 -0500
From: Gregory Price <gourry@...rry.net>
To: Bharata B Rao <bharata@....com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Jonathan.Cameron@...wei.com, dave.hansen@...el.com,
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	balbirs@...dia.com, alok.rathore@...sung.com, shivankg@....com
Subject: Re: [RFC PATCH v4 0/9] mm: Hot page tracking and promotion
 infrastructure

On Tue, Jan 13, 2026 at 08:08:34PM +0530, Bharata B Rao wrote:
> On 13-Jan-26 7:54 PM, Gregory Price wrote:
> > On Sat, Dec 06, 2025 at 03:44:14PM +0530, Bharata B Rao wrote:
> >> Hi,
> >>
> >> This is v4 of page hotness tracking and promotion sub-system pghot.
> >>
> > 
> > Just fyi, we haven't started real workload testing, but we're setting
> > up the process soon.  Just wanted to let you know it's on the radar.
> > 
> > We want to test this at the same time with some fixes we've been
> > working on for multi-tenant fairness in the demotion/reclaim path.
> 
> Thanks Gregory for taking this up for testing.
> 
> I am working on v5 with following enhancements:
> 
> 1. Default mode: 1 byte per PFN for storing hotness info. NID isn't stored but
> promotion will be done to a default toptier node(specifiable via sysfs/debugs).
> Frequency and time are stored but due to paucity of bits, I will have to use
> some sort of bucketing scheme for storing time like how current hot page
> promotion logic does.
> 
> 2. Precision mode: 4 bytes or 32bits per PFN where NID is stored in addition to
> time and frequency.
> 
> 2 is completed and 1 is in the works. Once I get it working correctly, I will
> post v5.
> 
> Since there were a few bugs in v4, I think it makes sense to start testing on v5
> itself.
>

Can do, thanks for the heads up, we'll wait for v5.

Cheers,
Gregory