From: Matthew Wilcox <willy@infradead.org>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: akpm@linux-foundation.org, darrick.wong@oracle.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/filemap.c: minor optimization in write_iter file operation
Date: Sun, 18 Nov 2018 04:13:18 -0800 [thread overview]
Message-ID: <20181118121318.GC7861@bombadil.infradead.org> (raw)
In-Reply-To: <1542542538-11938-1-git-send-email-laoar.shao@gmail.com>
On Sun, Nov 18, 2018 at 08:02:18PM +0800, Yafang Shao wrote:
> This little adjustment on bitwise operation could make the code a little
> faster.
> As write_iter is used in lots of critical path, so this code change is
> useful for performance.
Did you check the before/after code generation with this patch applied?
$ diff -u before.S after.S
--- before.S 2018-11-18 07:11:48.031096768 -0500
+++ after.S 2018-11-18 07:11:36.883069103 -0500
@@ -1,5 +1,5 @@
-before.o: file format elf32-i386
+after.o: file format elf32-i386
Disassembly of section .text:
with gcc 8.2.0, I see no difference, indicating that the compiler already
makes this optimisation.
next prev parent reply other threads:[~2018-11-18 12:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-18 12:02 [PATCH] mm/filemap.c: minor optimization in write_iter file operation Yafang Shao
2018-11-18 12:13 ` Matthew Wilcox [this message]
2018-11-18 15:02 ` Yafang Shao
2018-11-19 1:03 ` Matthew Wilcox
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