37fb3e4318
In pursuit of improving performance on multi-core systems, we should implements fanned out counters and use them to improve the performance of some of the arc statistics. These stats are updated extremely frequently, and can consume a significant amount of CPU time. Authored by: Paul Dagnelie <pcd@delphix.com> Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed by: Matthew Ahrens <mahrens@delphix.com> Approved by: Dan McDonald <danmcd@joyent.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Ported-by: Paul Dagnelie <pcd@delphix.com> OpenZFS-issue: https://www.illumos.org/issues/8484 OpenZFS-commit: https://github.com/openzfs/openzfs/commit/7028a8b92b7 Issue #3752 Closes #7462
64 lines
2.0 KiB
C
64 lines
2.0 KiB
C
// Copyright (c) 2011 Google, Inc.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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/*
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* Copyright (c) 2017 by Delphix. All rights reserved.
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*/
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#include <sys/cityhash.h>
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#define HASH_K1 0xb492b66fbe98f273ULL
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#define HASH_K2 0x9ae16a3b2f90404fULL
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/*
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* Bitwise right rotate. Normally this will compile to a single
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* instruction.
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*/
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static inline uint64_t
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rotate(uint64_t val, int shift)
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{
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// Avoid shifting by 64: doing so yields an undefined result.
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return (shift == 0 ? val : (val >> shift) | (val << (64 - shift)));
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}
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static inline uint64_t
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cityhash_helper(uint64_t u, uint64_t v, uint64_t mul)
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{
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uint64_t a = (u ^ v) * mul;
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a ^= (a >> 47);
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uint64_t b = (v ^ a) * mul;
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b ^= (b >> 47);
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b *= mul;
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return (b);
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}
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uint64_t
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cityhash4(uint64_t w1, uint64_t w2, uint64_t w3, uint64_t w4)
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{
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uint64_t mul = HASH_K2 + 64;
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uint64_t a = w1 * HASH_K1;
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uint64_t b = w2;
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uint64_t c = w4 * mul;
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uint64_t d = w3 * HASH_K2;
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return (cityhash_helper(rotate(a + b, 43) + rotate(c, 30) + d,
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a + rotate(b + HASH_K2, 18) + c, mul));
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}
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