diff options
author | Yunhong Jiang <yunhong.jiang@linux.intel.com> | 2017-03-08 23:13:28 -0800 |
---|---|---|
committer | Yunhong Jiang <yunhong.jiang@linux.intel.com> | 2017-03-08 23:36:15 -0800 |
commit | 52f993b8e89487ec9ee15a7fb4979e0f09a45b27 (patch) | |
tree | d65304486afe0bea4a311c783c0d72791c8c0aa2 /kernel/include/linux/hash.h | |
parent | c189ccac5702322ed843fe17057035b7222a59b6 (diff) |
Upgrade to 4.4.50-rt62
The current kernel is based on rt kernel v4.4.6-rt14. We will upgrade it
to 4.4.50-rt62.
The command to achieve it is:
a) Clone a git repo from
git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-stable-rt.git
b) Get the diff between this two changesets:
git diff 640eca2901f3435e616157b11379d3223a44b391
705619beeea1b0b48219a683fd1a901a86fdaf5e
where the two commits are:
[yjiang5@jnakajim-build linux-stable-rt]$ git show --oneline --name-only
640eca2901f3435e616157b11379d3223a44b391
640eca2901f3 v4.4.6-rt14
localversion-rt
[yjiang5@jnakajim-build linux-stable-rt]$ git show --oneline --name-only
705619beeea1b0b48219a683fd1a901a86fdaf5e
705619beeea1 Linux 4.4.50-rt62
localversion-rt
c) One patch has been backported thus revert the patch before applying.
filterdiff -p1 -x scripts/package/Makefile
~/tmp/v4.4.6-rt14-4.4.50-rt62.diff |patch -p1 --dry-run
Upstream status: backport
Change-Id: I244d57a32f6066e5a5b9915f9fbf99e7bbca6e01
Signed-off-by: Yunhong Jiang <yunhong.jiang@linux.intel.com>
Diffstat (limited to 'kernel/include/linux/hash.h')
-rw-r--r-- | kernel/include/linux/hash.h | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/kernel/include/linux/hash.h b/kernel/include/linux/hash.h index 1afde47e1..79c52fa81 100644 --- a/kernel/include/linux/hash.h +++ b/kernel/include/linux/hash.h @@ -32,12 +32,28 @@ #error Wordsize not 32 or 64 #endif +/* + * The above primes are actively bad for hashing, since they are + * too sparse. The 32-bit one is mostly ok, the 64-bit one causes + * real problems. Besides, the "prime" part is pointless for the + * multiplicative hash. + * + * Although a random odd number will do, it turns out that the golden + * ratio phi = (sqrt(5)-1)/2, or its negative, has particularly nice + * properties. + * + * These are the negative, (1 - phi) = (phi^2) = (3 - sqrt(5))/2. + * (See Knuth vol 3, section 6.4, exercise 9.) + */ +#define GOLDEN_RATIO_32 0x61C88647 +#define GOLDEN_RATIO_64 0x61C8864680B583EBull + static __always_inline u64 hash_64(u64 val, unsigned int bits) { u64 hash = val; -#if defined(CONFIG_ARCH_HAS_FAST_MULTIPLIER) && BITS_PER_LONG == 64 - hash = hash * GOLDEN_RATIO_PRIME_64; +#if BITS_PER_LONG == 64 + hash = hash * GOLDEN_RATIO_64; #else /* Sigh, gcc can't optimise this alone like it does for 32 bits. */ u64 n = hash; |