From: Xiao Wang <xiao.w.wang@intel.com>
To: paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu
Cc: jerry.shih@sifive.com, nick.knight@sifive.com,
ajones@ventanamicro.com, bjorn@rivosinc.com,
andy.chiu@sifive.com, viro@zeniv.linux.org.uk,
cleger@rivosinc.com, alexghiti@rivosinc.com,
haicheng.li@intel.com, linux-riscv@lists.infradead.org,
linux-kernel@vger.kernel.org, Xiao Wang <xiao.w.wang@intel.com>
Subject: [PATCH] riscv: uaccess: Relax the threshold for fast path
Date: Wed, 13 Mar 2024 17:19:29 +0800 [thread overview]
Message-ID: <20240313091929.4029960-1-xiao.w.wang@intel.com> (raw)
The bytes copy for unaligned head would cover at most SZREG-1 bytes, so
it's better to set the threshold as >= (SZREG-1 + word_copy stride size)
which equals to 9*SZREG-1.
Signed-off-by: Xiao Wang <xiao.w.wang@intel.com>
---
arch/riscv/lib/uaccess.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
index bc22c078aba8..2e665f8f8fcc 100644
--- a/arch/riscv/lib/uaccess.S
+++ b/arch/riscv/lib/uaccess.S
@@ -44,7 +44,7 @@ SYM_FUNC_START(fallback_scalar_usercopy)
* Use byte copy only if too small.
* SZREG holds 4 for RV32 and 8 for RV64
*/
- li a3, 9*SZREG /* size must be larger than size in word_copy */
+ li a3, 9*SZREG-1 /* size must >= (word_copy stride + SZREG-1) */
bltu a2, a3, .Lbyte_copy_tail
/*
--
2.25.1
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next reply other threads:[~2024-03-13 9:33 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-13 9:19 Xiao Wang [this message]
2024-05-03 12:14 ` [PATCH] riscv: uaccess: Relax the threshold for fast path Alexandre Ghiti
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