From: Mikulas Patocka <mpatocka@redhat.com>
To: Alexander Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@kernel.dk>
Cc: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org
Subject: [PATCH] buffer: a small optimization in grow_buffers
Date: Mon, 22 Mar 2021 10:05:05 -0400 (EDT) [thread overview]
Message-ID: <alpine.LRH.2.02.2103221002360.19948@file01.intranet.prod.int.rdu2.redhat.com> (raw)
This patch replaces a loop with a "tzcnt" instruction.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Index: linux-2.6/fs/buffer.c
===================================================================
--- linux-2.6.orig/fs/buffer.c
+++ linux-2.6/fs/buffer.c
@@ -1020,11 +1020,7 @@ grow_buffers(struct block_device *bdev,
pgoff_t index;
int sizebits;
- sizebits = -1;
- do {
- sizebits++;
- } while ((size << sizebits) < PAGE_SIZE);
-
+ sizebits = PAGE_SHIFT - __ffs(size);
index = block >> sizebits;
/*
next reply other threads:[~2021-03-22 14:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-22 14:05 Mikulas Patocka [this message]
2021-03-22 15:11 ` [PATCH] buffer: a small optimization in grow_buffers Matthew Wilcox
2021-03-22 16:36 ` Mikulas Patocka
2021-03-22 15:34 ` Al Viro
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