Re: [PATCH v3 mm-unstable] mm/damon/core: keep the temporal tuner quota over an unmeasured PSI round

[sashiko-bot@kernel.org]

> From: Karl Mehltretter <kmehltretter@gmail.com>
> 
> The patch in mm-unstable of subject "mm/damon/core: handle uninitialized
> damos_quota_goal->last_psi_total" scores a PSI quota goal without a
> previous sample as achieved. This leaves the consist tuner's input
> unchanged, but the temporal tuner sets its quota to zero for an achieved
> goal. A running scheme with a nonzero temporal quota therefore loses a
> charge window after a quota-goal commit.
> 
> Use the effective quota to preserve the temporal tuner's previous
> goal-achievement state during an unmeasured round, as SJ suggested [1].
> Score the goal as achieved when the effective quota is zero and as not
> achieved otherwise. A new scheme's initially zero quota stays zero, and
> the consist tuner's behavior is unchanged.
> 
> Move the PSI current-value calculation and last_psi_total update into a
> helper that takes the current PSI total. This lets a unit test cover the
> unmeasured and measured rounds without depending on system memory
> pressure.
> 
> Link: https://lore.kernel.org/damon/20260916001311.101024-1-sj@kernel.org/ [1]
> Fixes: 2dbb60f789cb ("mm/damon/core: implement PSI metric DAMOS quota goal")
> Cc: <stable@vger.kernel.org> # 6.9.x
> Cc: Lian Wang <lianux.mm@gmail.com>
> Cc: Kunwu Chan <kunwu.chan@gmail.com>
> Suggested-by: SJ Park <sj@kernel.org>
> Assisted-by: LLM
> Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
> Reviewed-by: SJ Park <sj@kernel.org>
> Signed-off-by: SJ Park <sj@kernel.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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