[no subject]

From: Alessio Igor Bogani
Date: Wed May 18 2011 - 14:55:50 EST

Dear Mr. Bird, Dear Mr. Kroah-Hartman,

Sorry for my very bad English.

2011/5/18 Tim Bird <tim.bird@xxxxxxxxxxx>:
> Alessio - do you have any timings you can share for the speedup?

You can find a little benchmark using ftrace at end of this email:

> On 05/17/2011 04:22 PM, Greg KH wrote:
>> On Tue, May 17, 2011 at 10:56:03PM +0200, Alessio Igor Bogani wrote:
>>> This work was supported by a hardware donation from the CE Linux Forum.
>> Please explain why you make a change, not just who sponsored the change,
>> that's not very interesting to developers.

You are right. I apologize.

This patch is a missing piece (not essential it is only a further little
optimization) of this little patchset:

Unfortunately I forgot to include this patch in the series (my first error)
then I avoided explaining the changes because I had thought that those were
already enough explained in the cover-letter of the patchset (my second error).

Sorry for my mistakes.

Is this better?

Subject: [PATCH] module: Use binary search in lookup_symbol()

The function is_exported() with its helper function lookup_symbol() are used to
verify if a provided symbol is effectively exported by the kernel or by the
modules. Now that both have their symbols sorted we can replace a linear search
with a binary search which provide a considerably speed-up.

This work was supported by a hardware donation from the CE Linux Forum.

Signed-off-by: Alessio Igor Bogani <abogani@xxxxxxxxxx>
kernel/module.c | 7 ++-----
1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 1e2b657..795bdc7 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2055,11 +2055,8 @@ static const struct kernel_symbol *lookup_symbol(const char *name,
const struct kernel_symbol *start,
const struct kernel_symbol *stop)
- const struct kernel_symbol *ks = start;
- for (; ks < stop; ks++)
- if (strcmp(ks->name, name) == 0)
- return ks;
- return NULL;
+ return bsearch(name, start, stop - start,
+ sizeof(struct kernel_symbol), cmp_name);

static int is_exported(const char *name, unsigned long value,

Thank you very much!

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/