Merge branch 'ovs_hash'

Francesco Fusco says:

====================
ovs: introduce arch-specific fast hashing improvements

From: Daniel Borkmann <dborkman@redhat.com>

We are introducing a fast hash function (see patch1) that can be
used in the context of OpenVSwitch to reduce the hashing footprint
(patch2). For details, please see individual patches!

v1->v2:
 - Make hash generic and place it under lib
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2013-12-17 14:27:44 -05:00
commit bc4d0f615a
8 changed files with 182 additions and 4 deletions

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@ -0,0 +1,7 @@
#ifndef _ASM_X86_HASH_H
#define _ASM_X86_HASH_H
struct fast_hash_ops;
extern void setup_arch_fast_hash(struct fast_hash_ops *ops);
#endif /* _ASM_X86_HASH_H */

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@ -24,7 +24,7 @@ lib-$(CONFIG_SMP) += rwlock.o
lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o
obj-y += msr.o msr-reg.o msr-reg-export.o
obj-y += msr.o msr-reg.o msr-reg-export.o hash.o
ifeq ($(CONFIG_X86_32),y)
obj-y += atomic64_32.o

88
arch/x86/lib/hash.c Normal file
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@ -0,0 +1,88 @@
/*
* Some portions derived from code covered by the following notice:
*
* Copyright (c) 2010-2013 Intel Corporation. All rights reserved.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Intel Corporation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <linux/hash.h>
#include <asm/processor.h>
#include <asm/cpufeature.h>
#include <asm/hash.h>
static inline u32 crc32_u32(u32 crc, u32 val)
{
asm ("crc32l %1,%0\n" : "+r" (crc) : "rm" (val));
return crc;
}
static u32 intel_crc4_2_hash(const void *data, u32 len, u32 seed)
{
const u32 *p32 = (const u32 *) data;
u32 i, tmp = 0;
for (i = 0; i < len / 4; i++)
seed = crc32_u32(*p32++, seed);
switch (3 - (len & 0x03)) {
case 0:
tmp |= *((const u8 *) p32 + 2) << 16;
/* fallthrough */
case 1:
tmp |= *((const u8 *) p32 + 1) << 8;
/* fallthrough */
case 2:
tmp |= *((const u8 *) p32);
seed = crc32_u32(tmp, seed);
default:
break;
}
return seed;
}
static u32 intel_crc4_2_hash2(const u32 *data, u32 len, u32 seed)
{
const u32 *p32 = (const u32 *) data;
u32 i;
for (i = 0; i < len; i++)
seed = crc32_u32(*p32++, seed);
return seed;
}
void setup_arch_fast_hash(struct fast_hash_ops *ops)
{
if (cpu_has_xmm4_2) {
ops->hash = intel_crc4_2_hash;
ops->hash2 = intel_crc4_2_hash2;
}
}

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@ -0,0 +1,9 @@
#ifndef __ASM_GENERIC_HASH_H
#define __ASM_GENERIC_HASH_H
struct arch_hash_ops;
static inline void setup_arch_fast_hash(struct arch_hash_ops *ops)
{
}
#endif /* __ASM_GENERIC_HASH_H */

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@ -15,6 +15,7 @@
*/
#include <asm/types.h>
#include <asm/hash.h>
#include <linux/compiler.h>
/* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
@ -78,4 +79,39 @@ static inline u32 hash32_ptr(const void *ptr)
#endif
return (u32)val;
}
struct fast_hash_ops {
u32 (*hash)(const void *data, u32 len, u32 seed);
u32 (*hash2)(const u32 *data, u32 len, u32 seed);
};
/**
* arch_fast_hash - Caclulates a hash over a given buffer that can have
* arbitrary size. This function will eventually use an
* architecture-optimized hashing implementation if
* available, and trades off distribution for speed.
*
* @data: buffer to hash
* @len: length of buffer in bytes
* @seed: start seed
*
* Returns 32bit hash.
*/
extern u32 arch_fast_hash(const void *data, u32 len, u32 seed);
/**
* arch_fast_hash2 - Caclulates a hash over a given buffer that has a
* size that is of a multiple of 32bit words. This
* function will eventually use an architecture-
* optimized hashing implementation if available,
* and trades off distribution for speed.
*
* @data: buffer to hash (must be 32bit padded)
* @len: number of 32bit words
* @seed: start seed
*
* Returns 32bit hash.
*/
extern u32 arch_fast_hash2(const u32 *data, u32 len, u32 seed);
#endif /* _LINUX_HASH_H */

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@ -26,7 +26,7 @@ obj-y += bcd.o div64.o sort.o parser.o halfmd4.o debug_locks.o random32.o \
bust_spinlocks.o hexdump.o kasprintf.o bitmap.o scatterlist.o \
gcd.o lcm.o list_sort.o uuid.o flex_array.o iovec.o clz_ctz.o \
bsearch.o find_last_bit.o find_next_bit.o llist.o memweight.o kfifo.o \
percpu-refcount.o percpu_ida.o
percpu-refcount.o percpu_ida.o hash.o
obj-y += string_helpers.o
obj-$(CONFIG_TEST_STRING_HELPERS) += test-string_helpers.o
obj-y += kstrtox.o

38
lib/hash.c Normal file
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@ -0,0 +1,38 @@
/* General purpose hashing library
*
* That's a start of a kernel hashing library, which can be extended
* with further algorithms in future. arch_fast_hash{2,}() will
* eventually resolve to an architecture optimized implementation.
*
* Copyright 2013 Francesco Fusco <ffusco@redhat.com>
* Copyright 2013 Daniel Borkmann <dborkman@redhat.com>
* Copyright 2013 Thomas Graf <tgraf@redhat.com>
* Licensed under the GNU General Public License, version 2.0 (GPLv2)
*/
#include <linux/jhash.h>
#include <linux/hash.h>
static struct fast_hash_ops arch_hash_ops __read_mostly = {
.hash = jhash,
.hash2 = jhash2,
};
u32 arch_fast_hash(const void *data, u32 len, u32 seed)
{
return arch_hash_ops.hash(data, len, seed);
}
EXPORT_SYMBOL_GPL(arch_fast_hash);
u32 arch_fast_hash2(const u32 *data, u32 len, u32 seed)
{
return arch_hash_ops.hash2(data, len, seed);
}
EXPORT_SYMBOL_GPL(arch_fast_hash2);
static int __init hashlib_init(void)
{
setup_arch_fast_hash(&arch_hash_ops);
return 0;
}
early_initcall(hashlib_init);

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@ -25,7 +25,7 @@
#include <linux/if_vlan.h>
#include <net/llc_pdu.h>
#include <linux/kernel.h>
#include <linux/jhash.h>
#include <linux/hash.h>
#include <linux/jiffies.h>
#include <linux/llc.h>
#include <linux/module.h>
@ -362,7 +362,7 @@ static u32 flow_hash(const struct sw_flow_key *key, int key_start,
/* Make sure number of hash bytes are multiple of u32. */
BUILD_BUG_ON(sizeof(long) % sizeof(u32));
return jhash2(hash_key, hash_u32s, 0);
return arch_fast_hash2(hash_key, hash_u32s, 0);
}
static int flow_key_start(const struct sw_flow_key *key)