From 5ecc0a0f8128b1876e8614638deaed49cc8b174c Mon Sep 17 00:00:00 2001 From: Sage Weil Date: Tue, 6 Oct 2009 11:31:11 -0700 Subject: ceph: CRUSH mapping algorithm CRUSH is a pseudorandom data distribution function designed to map inputs onto a dynamic hierarchy of devices, while minimizing the extent to which inputs are remapped when the devices are added or removed. It includes some features that are specifically useful for storage, most notably the ability to map each input onto a set of N devices that are separated across administrator-defined failure domains. CRUSH is used to distribute data across the cluster of Ceph storage nodes. More information about CRUSH can be found in this paper: http://www.ssrc.ucsc.edu/Papers/weil-sc06.pdf Signed-off-by: Sage Weil --- fs/ceph/crush/hash.h | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 fs/ceph/crush/hash.h (limited to 'fs/ceph/crush/hash.h') diff --git a/fs/ceph/crush/hash.h b/fs/ceph/crush/hash.h new file mode 100644 index 000000000000..42f3312783a1 --- /dev/null +++ b/fs/ceph/crush/hash.h @@ -0,0 +1,90 @@ +#ifndef _CRUSH_HASH_H +#define _CRUSH_HASH_H + +/* + * Robert Jenkins' function for mixing 32-bit values + * http://burtleburtle.net/bob/hash/evahash.html + * a, b = random bits, c = input and output + */ +#define crush_hashmix(a, b, c) do { \ + a = a-b; a = a-c; a = a^(c>>13); \ + b = b-c; b = b-a; b = b^(a<<8); \ + c = c-a; c = c-b; c = c^(b>>13); \ + a = a-b; a = a-c; a = a^(c>>12); \ + b = b-c; b = b-a; b = b^(a<<16); \ + c = c-a; c = c-b; c = c^(b>>5); \ + a = a-b; a = a-c; a = a^(c>>3); \ + b = b-c; b = b-a; b = b^(a<<10); \ + c = c-a; c = c-b; c = c^(b>>15); \ + } while (0) + +#define crush_hash_seed 1315423911 + +static inline __u32 crush_hash32(__u32 a) +{ + __u32 hash = crush_hash_seed ^ a; + __u32 b = a; + __u32 x = 231232; + __u32 y = 1232; + crush_hashmix(b, x, hash); + crush_hashmix(y, a, hash); + return hash; +} + +static inline __u32 crush_hash32_2(__u32 a, __u32 b) +{ + __u32 hash = crush_hash_seed ^ a ^ b; + __u32 x = 231232; + __u32 y = 1232; + crush_hashmix(a, b, hash); + crush_hashmix(x, a, hash); + crush_hashmix(b, y, hash); + return hash; +} + +static inline __u32 crush_hash32_3(__u32 a, __u32 b, __u32 c) +{ + __u32 hash = crush_hash_seed ^ a ^ b ^ c; + __u32 x = 231232; + __u32 y = 1232; + crush_hashmix(a, b, hash); + crush_hashmix(c, x, hash); + crush_hashmix(y, a, hash); + crush_hashmix(b, x, hash); + crush_hashmix(y, c, hash); + return hash; +} + +static inline __u32 crush_hash32_4(__u32 a, __u32 b, __u32 c, + __u32 d) +{ + __u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d; + __u32 x = 231232; + __u32 y = 1232; + crush_hashmix(a, b, hash); + crush_hashmix(c, d, hash); + crush_hashmix(a, x, hash); + crush_hashmix(y, b, hash); + crush_hashmix(c, x, hash); + crush_hashmix(y, d, hash); + return hash; +} + +static inline __u32 crush_hash32_5(__u32 a, __u32 b, __u32 c, + __u32 d, __u32 e) +{ + __u32 hash = crush_hash_seed ^ a ^ b ^ c ^ d ^ e; + __u32 x = 231232; + __u32 y = 1232; + crush_hashmix(a, b, hash); + crush_hashmix(c, d, hash); + crush_hashmix(e, x, hash); + crush_hashmix(y, a, hash); + crush_hashmix(b, x, hash); + crush_hashmix(y, c, hash); + crush_hashmix(d, x, hash); + crush_hashmix(y, e, hash); + return hash; +} + +#endif -- cgit v1.2.2