On Mon, Dec 12, 2016 at 10:44 PM, Jason A. Donenfeld wrote:
> #if defined(CONFIG_DCACHE_WORD_ACCESS) && BITS_PER_LONG == 64
>switch (left) {
>case 0: break;
>case 1: b |= data[0]; break;
>case 2: b |= get_unaligned_le16(data); break;
>case 4: b |= get_unalig
Hi Linus,
> I guess you could try to just remove the "if (left)" test entirely, if
> it is at least partly the mispredict. It should do the right thing
> even with a zero count, and it might schedule the code better. Code
> size _should_ be better with the byte mask model (which won't matter
> in
On Sun, Dec 11, 2016 at 9:48 PM, Jason A. Donenfeld wrote:
> I modified the test to hash data of size 0 through 7 repeatedly
> 1 times, and benchmarked that a few times on a Skylake laptop.
> The `load_unaligned_zeropad & bytemask_from_count` version was
> consistently 7% slower.
>
> I the
Hey Eric,
Lots of good points; thanks for the review. Responses are inline below.
On Mon, Dec 12, 2016 at 6:42 AM, Eric Biggers wrote:
> Maybe add to the help text for CONFIG_TEST_HASH that it now tests siphash too?
Good call. Will do.
> This assumes the key and message buffers are aligned to
Hey Linus,
On Mon, Dec 12, 2016 at 5:01 AM, Linus Torvalds
wrote:
> The above is extremely inefficient. Considering that most kernel data
> would be expected to be smallish, that matters (ie the usual benchmark
> would not be about hashing megabytes of data, but instead millions of
> hashes of sm
On Mon, Dec 12, 2016 at 04:48:17AM +0100, Jason A. Donenfeld wrote:
>
> diff --git a/lib/Makefile b/lib/Makefile
> index 50144a3aeebd..71d398b04a74 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -22,7 +22,8 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
>sha1.o chacha20.o md5.o
On Sun, Dec 11, 2016 at 7:48 PM, Jason A. Donenfeld wrote:
> + switch (left) {
> + case 7: b |= ((u64)data[6]) << 48;
> + case 6: b |= ((u64)data[5]) << 40;
> + case 5: b |= ((u64)data[4]) << 32;
> + case 4: b |= ((u64)data[3]) << 24;
>
SipHash is a 64-bit keyed hash function that is actually a
cryptographically secure PRF, like HMAC. Except SipHash is super fast,
and is meant to be used as a hashtable keyed lookup function.
SipHash isn't just some new trendy hash function. It's been around for a
while, and there really isn't any
