linux-kernel - Re: [PATCH v1] mm/contpte: Optimize loop to reduce redundant operations

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Message-ID: <20250407112922.17766-1-ioworker0@gmail.com>
Date: Mon,  7 Apr 2025 19:29:22 +0800
From: Lance Yang <ioworker0@...il.com>
To: xavier_qy@....com
Cc: akpm@...ux-foundation.org,
	baohua@...nel.org,
	catalin.marinas@....com,
	ioworker0@...il.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	ryan.roberts@....com,
	will@...nel.org
Subject: Re: [PATCH v1] mm/contpte: Optimize loop to reduce redundant operations

Thanks for the patch. Would the following change be better?

diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
index 55107d27d3f8..64eb3b2fbf06 100644
--- a/arch/arm64/mm/contpte.c
+++ b/arch/arm64/mm/contpte.c
@@ -174,6 +174,9 @@ pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte)
 
 		if (pte_young(pte))
 			orig_pte = pte_mkyoung(orig_pte);
+
+		if (pte_young(orig_pte) && pte_dirty(orig_pte))
+			break;
 	}
 
 	return orig_pte;
-- 

We can check the orig_pte flags directly instead of using extra boolean
variables, which gives us an early-exit when both dirty and young flags
are set.

Also, is this optimization really needed for the common case?

Thanks,
Lance