2016-08-19 12:19:50

by Martin Schwidefsky

Subject: [PATCH] crypto/xor: skip speed test if the xor function is selected automatically

If the architecture selected the xor function with XOR_SELECT_TEMPLATE
the speed result of the do_xor_speed benchmark is of limited value.
The speed measurement increases the bootup time a little, which can
makes a difference for kernels used in container like virtual machines.

Signed-off-by: Martin Schwidefsky <[email protected]>
---
crypto/xor.c | 40 +++++++++++++++++++---------------------
1 file changed, 19 insertions(+), 21 deletions(-)

diff --git a/crypto/xor.c b/crypto/xor.c
index 35d6b3a..b8975d9 100644
--- a/crypto/xor.c
+++ b/crypto/xor.c
@@ -109,6 +109,18 @@ calibrate_xor_blocks(void)
void *b1, *b2;
struct xor_block_template *f, *fastest;

+ fastest = NULL;
+
+#ifdef XOR_SELECT_TEMPLATE
+ fastest = XOR_SELECT_TEMPLATE(fastest);
+ if (fastest) {
+ printk(KERN_INFO "xor: automatically using best "
+ "checksumming function %-10s\n",
+ fastest->name);
+ goto out;
+ }
+#endif
+
/*
* Note: Since the memory is not actually used for _anything_ but to
* test the XOR speed, we don't really want kmemcheck to warn about
@@ -126,36 +138,22 @@ calibrate_xor_blocks(void)
* all the possible functions, just test the best one
*/

- fastest = NULL;
-
-#ifdef XOR_SELECT_TEMPLATE
- fastest = XOR_SELECT_TEMPLATE(fastest);
-#endif
-
#define xor_speed(templ) do_xor_speed((templ), b1, b2)

- if (fastest) {
- printk(KERN_INFO "xor: automatically using best "
- "checksumming function:\n");
- xor_speed(fastest);
- goto out;
- } else {
- printk(KERN_INFO "xor: measuring software checksum speed\n");
- XOR_TRY_TEMPLATES;
- fastest = template_list;
- for (f = fastest; f; f = f->next)
- if (f->speed > fastest->speed)
- fastest = f;
- }
+ printk(KERN_INFO "xor: measuring software checksum speed\n");
+ XOR_TRY_TEMPLATES;
+ fastest = template_list;
+ for (f = fastest; f; f = f->next)
+ if (f->speed > fastest->speed)
+ fastest = f;

printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
fastest->name, fastest->speed / 1000, fastest->speed % 1000);

#undef xor_speed

- out:
free_pages((unsigned long)b1, 2);
-
+out:
active_template = fastest;
return 0;
}
--
1.9.1

2016-08-24 13:17:13

by Herbert Xu

Subject: Re: [PATCH] crypto/xor: skip speed test if the xor function is selected automatically

Martin Schwidefsky <[email protected]> wrote:
> If the architecture selected the xor function with XOR_SELECT_TEMPLATE
> the speed result of the do_xor_speed benchmark is of limited value.
> The speed measurement increases the bootup time a little, which can
> makes a difference for kernels used in container like virtual machines.
>
> Signed-off-by: Martin Schwidefsky <[email protected]>

Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt