blob: d735e684ef6073bfc0ecd4c2643ed87be4088f27 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
|
// Copyright 2006 Google Inc. All Rights Reserved.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// queue.cc : simple thread safe queue implementation
#include <stdlib.h>
// This file must work with autoconf on its public version,
// so these includes are correct.
#include "queue.h"
#include "sattypes.h"
// Page entry queue implementation follows.
// Push inserts pages, pop returns a random entry.
PageEntryQueue::PageEntryQueue(uint64 queuesize) {
// There must always be one empty queue location,
// since in == out => empty.
q_size_ = queuesize + 1;
pages_ = new struct page_entry[q_size_];
nextin_ = 0;
nextout_ = 0;
popped_ = 0;
pushed_ = 0;
pthread_mutex_init(&q_mutex_, NULL);
}
PageEntryQueue::~PageEntryQueue() {
delete[] pages_;
pthread_mutex_destroy(&q_mutex_);
}
// Add a page into this queue.
int PageEntryQueue::Push(struct page_entry *pe) {
int result = 0;
int64 nextnextin;
if (!pe)
return 0;
pthread_mutex_lock(&q_mutex_);
nextnextin = (nextin_ + 1) % q_size_;
if (nextnextin != nextout_) {
pages_[nextin_] = *pe;
nextin_ = nextnextin;
result = 1;
pushed_++;
}
pthread_mutex_unlock(&q_mutex_);
return result;
}
// Retrieve a random page from this queue.
int PageEntryQueue::PopRandom(struct page_entry *pe) {
int result = 0;
int64 lastin;
int64 entries;
int64 newindex;
struct page_entry tmp;
if (!pe)
return 0;
// TODO(nsanders): we should improve random to get 64 bit randoms, and make
// it more thread friendly.
uint64 rand = random();
int retval = pthread_mutex_lock(&q_mutex_);
if (retval)
logprintf(0, "Process Error: pthreads mutex failure %d\n", retval);
if (nextin_ != nextout_) {
// Randomized fetch.
// Swap random entry with next out.
{
lastin = (nextin_ - 1 + q_size_) % q_size_;
entries = (lastin - nextout_ + q_size_) % q_size_;
newindex = nextout_;
if (entries)
newindex = ((rand % entries) + nextout_) % q_size_;
// Swap the pages.
tmp = pages_[nextout_];
pages_[nextout_] = pages_[newindex];
pages_[newindex] = tmp;
}
// Return next out page.
*pe = pages_[nextout_];
nextout_ = (nextout_ + 1) % q_size_;
result = 1;
popped_++;
}
pthread_mutex_unlock(&q_mutex_);
return result;
}
|
