linux-kernel - Re: [PATCH 6.1.y] mm/damon/reclaim: fix quota stauts loss due to online tunings

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Message-ID: <2024022731-varying-underpaid-c855@gregkh>
Date: Tue, 27 Feb 2024 10:19:41 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: SeongJae Park <sj@...nel.org>
Cc: stable@...r.kernel.org, damon@...ts.linux.dev, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 6.1.y] mm/damon/reclaim: fix quota stauts loss due to
 online tunings

On Mon, Feb 26, 2024 at 09:13:35PM -0800, SeongJae Park wrote:
> Patch series "mm/damon: fix quota status loss due to online tunings".
> 
> DAMON_RECLAIM and DAMON_LRU_SORT is not preserving internal quota status
> when applying new user parameters, and hence could cause temporal quota
> accuracy degradation.  Fix it by preserving the status.
> 
> This patch (of 2):
> 
> For online parameters change, DAMON_RECLAIM creates new scheme based on
> latest values of the parameters and replaces the old scheme with the new
> one.  When creating it, the internal status of the quota of the old
> scheme is not preserved.  As a result, charging of the quota starts from
> zero after the online tuning.  The data that collected to estimate the
> throughput of the scheme's action is also reset, and therefore the
> estimation should start from the scratch again.  Because the throughput
> estimation is being used to convert the time quota to the effective size
> quota, this could result in temporal time quota inaccuracy.  It would be
> recovered over time, though.  In short, the quota accuracy could be
> temporarily degraded after online parameters update.
> 
> Fix the problem by checking the case and copying the internal fields for
> the status.
> 
> Link: https://lkml.kernel.org/r/20240216194025.9207-1-sj@kernel.org
> Link: https://lkml.kernel.org/r/20240216194025.9207-2-sj@kernel.org
> Fixes: e035c280f6df ("mm/damon/reclaim: support online inputs update")
> Signed-off-by: SeongJae Park <sj@...nel.org>
> Cc: <stable@...r.kernel.org>	[5.19+]
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> (cherry picked from commit 1b0ca4e4ff10a2c8402e2cf70132c683e1c772e4)
> ---
>  mm/damon/reclaim.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 

Now queued up, thanks.

greg k-h