linux-kernel - [PATCH 04/20] ARCv2: memset: don't prefetch for len == 0 which happens a alot

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Message-Id: <20230815004813.555115-5-vgupta@kernel.org>
Date:   Mon, 14 Aug 2023 17:47:57 -0700
From:   Vineet Gupta <vgupta@...nel.org>
To:     linux-snps-arc@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org,
        Shahab Vahedi <Shahab.Vahedi@...opsys.com>,
        Alexey Brodkin <abrodkin@...opsys.com>,
        Vineet Gupta <vgupta@...nel.org>
Subject: [PATCH 04/20] ARCv2: memset: don't prefetch for len == 0 which happens a alot

This avoids potential "bleeding" when size == 0 as cache line would be
dirtied (and possibly fetched from other cores) and due to the same
reaons more optimal too.

Signed-off-by: Vineet Gupta <vgupta@...nel.org>
---
 arch/arc/lib/memset-archs.S | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arc/lib/memset-archs.S b/arch/arc/lib/memset-archs.S
index d2e09fece5bc..d0a5cec4cdca 100644
--- a/arch/arc/lib/memset-archs.S
+++ b/arch/arc/lib/memset-archs.S
@@ -36,12 +36,13 @@
 #endif
 
 ENTRY_CFI(memset)
-	PREFETCHW_INSTR	r0, 0	; Prefetch the first write location
 	mov.f	0, r2
 ;;; if size is zero
 	jz.d	[blink]
 	mov	r3, r0		; don't clobber ret val
 
+	PREFETCHW_INSTR	r0, 0	; Prefetch the first write location
+
 ;;; if length < 8
 	brls.d.nt	r2, 8, .Lsmallchunk
 	mov.f	lp_count,r2
-- 
2.34.1