On Thursday, June 05, 2014 at 03:11:33 AM, Amos Kong wrote:
> In crypto/xor.c: calibrate_xor_blocks(), we allocated total 4 pages to
> do xor speed testing, the BENCH_SIZE is 1 page, and we skipped 2 pages
> when we set b2.
>
> It seems that total 2 pages are enough without skipping 2 pages.
>
> Signed-off-by: Amos Kong <akong@xxxxxxxxxx>
> ---
> crypto/xor.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/crypto/xor.c b/crypto/xor.c
> index 35d6b3a..609dfb5 100644
> --- a/crypto/xor.c
> +++ b/crypto/xor.c
> @@ -114,12 +114,12 @@ calibrate_xor_blocks(void)
> * test the XOR speed, we don't really want kmemcheck to warn about
> * reading uninitialized bytes here.
> */
> - b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);
> + b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 1);
> if (!b1) {
> printk(KERN_WARNING "xor: Yikes! No memory available.\n");
> return -ENOMEM;
> }
> - b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
> + b2 = b1 + BENCH_SIZE;
>
> /*
> * If this arch/cpu has a short-circuited selection, don't loop through
> @@ -154,7 +154,7 @@ calibrate_xor_blocks(void)
> #undef xor_speed
>
> out:
> - free_pages((unsigned long)b1, 2);
> + free_pages((unsigned long)b1, 1);
>
> active_template = fastest;
> return 0;
I think this does make sense, but I am not 100% sure, sorry.
...
While looking at this code, can anyone explain to me why we have this stuff in
crypto/xor.c please ?
135 #define xor_speed(templ) do_xor_speed((templ), b1, b2)
136
137 if (fastest) {
138 printk(KERN_INFO "xor: automatically using best "
139 "checksumming function:\n");
140 xor_speed(fastest);
141 goto out;
142 } else {
[...]
149 }
150
151 printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
152 fastest->name, fastest->speed / 1000, fastest->speed % 1000);
153
154 #undef xor_speed
Why do we not call do_xor_speed(fastest, b1, b2); right away , but we #define
xor_speed() instead ? This looks like some remnant or nonsense to me. Shall I
remove that with a patch ?
Best regards,
Marek Vasut
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