linux-kernel - Re: [PATCH v2] mm/page_alloc: Avoid duplicate NR_FREE_PAGES updates in move_to_free

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Message-ID: <20260112145320.3748979-1-joshua.hahnjy@gmail.com>
Date: Mon, 12 Jan 2026 06:53:19 -0800
From: Joshua Hahn <joshua.hahnjy@...il.com>
To: Yajun Deng <yajun.deng@...ux.dev>
Cc: akpm@...ux-foundation.org,
	vbabka@...e.cz,
	surenb@...gle.com,
	mhocko@...e.com,
	jackmanb@...gle.com,
	hannes@...xchg.org,
	ziy@...dia.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm/page_alloc: Avoid duplicate NR_FREE_PAGES updates in move_to_free_list()

On Mon, 12 Jan 2026 20:16:14 +0800 Yajun Deng <yajun.deng@...ux.dev> wrote:

> In move_to_free_list(), when a page block changes its migration type,
> we need to update free page counts for both the old and new types.
> Originally, this was done by two calls to account_freepages(), which
> updates NR_FREE_PAGES and also type-specific counters. However, this
> causes NR_FREE_PAGES to be updated twice, while the net change is zero
> in most cases.
> 
> This patch adds a condition that updates the NR_FREE_PAGES only if one of
> the two types is the isolate type. This avoids NR_FREE_PAGES being
> updates twice.
> 
> The optimization avoid duplicate NR_FREE_PAGES updates in
> move_to_free_list().
> 
> Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
> Suggested-by: Joshua Hahn <joshua.hahnjy@...il.com>

Hello Yajun,

LGTM. Thank you for kindly accepting my suggestion!
Reviewed-by: Joshua Hahn <joshua.hahnjy@...il.com>