linux-kernel - [PATCH v2 3/3] page-types: exit early when invoked with -d|--describe

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Date:	Thu, 05 Nov 2009 13:21:26 -0700
From:	Alex Chiang <achiang@...com>
To:	akpm@...ux-foundation.org, fengguang.wu@...el.com
Cc:	Haicheng Li <haicheng.li@...el.com>, linux-mm@...ck.org,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/3] page-types: exit early when invoked with -d|--describe

On a system with large amount of memory (256GB), invoking page-types
can take quite a long time, which is unreasonable considering the user
only wants a description of the flags:

	# time ./page-types -d 0x10
	0x0000000000000010	____D_____________________________	dirty

	real	0m34.285s
	user	0m1.966s
	sys	0m32.313s

This is because we still walk the entire address range.

Exiting early seems like a reasonble solution:

# time ./page-types -d 0x10
	0x0000000000000010	____D_____________________________	dirty

	real	0m0.007s
	user	0m0.001s
	sys	0m0.005s

Cc: Andi Kleen <andi@...stfloor.org>
Cc: Haicheng Li <haicheng.li@...el.com>
Signed-off-by: Alex Chiang <achiang@...com>
---

 Documentation/vm/page-types.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/Documentation/vm/page-types.c b/Documentation/vm/page-types.c
index 9c09eb5..9cf50ab 100644
--- a/Documentation/vm/page-types.c
+++ b/Documentation/vm/page-types.c
@@ -940,9 +940,8 @@ int main(int argc, char *argv[])
 			parse_bits_mask(optarg);
 			break;
 		case 'd':
-			opt_no_summary = 1;
 			describe_flags(optarg);
-			break;
+			exit(0);
 		case 'l':
 			opt_list = 1;
 			break;

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