scrub/counter.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (C) 2018 Oracle.  All Rights Reserved.
   4  * Author: Darrick J. Wong <darrick.wong@oracle.com>
   5  */
   6 #include "xfs.h"
   7 #include <stdint.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <assert.h>
  11 #include <pthread.h>
  12 #include "libfrog/ptvar.h"
  13 #include "counter.h"
  14
  15 /*
  16  * Per-Thread Counters
  17  *
  18  * This is a global counter object that uses per-thread counters to
  19  * count things without having to content for a single shared lock.
  20  * Provided we know the number of threads that will be accessing the
  21  * counter, each thread gets its own thread-specific counter variable.
  22  * Changing the value is fast, though retrieving the value is expensive
  23  * and approximate.
  24  */
  25 struct ptcounter {
  26         struct ptvar    *var;
  27 };
  28
  29 /* Initialize per-thread counter. */
  30 struct ptcounter *
  31 ptcounter_init(
  32         size_t                  nr)
  33 {
  34         struct ptcounter        *p;
  35
  36         p = malloc(sizeof(struct ptcounter));
  37         if (!p)
  38                 return NULL;
  39         p->var = ptvar_init(nr, sizeof(uint64_t));
  40         if (!p->var) {
  41                 free(p);
  42                 return NULL;
  43         }
  44         return p;
  45 }
  46
  47 /* Free per-thread counter. */
  48 void
  49 ptcounter_free(
  50         struct ptcounter        *ptc)
  51 {
  52         ptvar_free(ptc->var);
  53         free(ptc);
  54 }
  55
  56 /* Add a quantity to the counter. */
  57 void
  58 ptcounter_add(
  59         struct ptcounter        *ptc,
  60         int64_t                 nr)
  61 {
  62         uint64_t                *p;
  63
  64         p = ptvar_get(ptc->var);
  65         *p += nr;
  66 }
  67
  68 static bool
  69 ptcounter_val_helper(
  70         struct ptvar            *ptv,
  71         void                    *data,
  72         void                    *foreach_arg)
  73 {
  74         uint64_t                *sum = foreach_arg;
  75         uint64_t                *count = data;
  76
  77         *sum += *count;
  78         return true;
  79 }
  80
  81 /* Return the approximate value of this counter. */
  82 uint64_t
  83 ptcounter_value(
  84         struct ptcounter        *ptc)
  85 {
  86         uint64_t                sum = 0;
  87
  88         ptvar_foreach(ptc->var, ptcounter_val_helper, &sum);
  89         return sum;
  90 }