module/zfs/zfs_ratelimit.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright (c) 2017, Lawrence Livermore National Security, LLC.
  24  */
  25
  26 #include <sys/zfs_ratelimit.h>
  27
  28 /*
  29  * Initialize rate limit struct
  30  *
  31  * rl:          zfs_ratelimit_t struct
  32  * burst:       Number to allow in an interval before rate limiting
  33  * interval:    Interval time in seconds
  34  */
  35 void
  36 zfs_ratelimit_init(zfs_ratelimit_t *rl, unsigned int burst,
  37     unsigned int interval)
  38 {
  39         rl->count = 0;
  40         rl->start = 0;
  41         rl->interval = interval;
  42         rl->burst = burst;
  43         mutex_init(&rl->lock, NULL, MUTEX_DEFAULT, NULL);
  44 }
  45
  46 /*
  47  * Finalize rate limit struct
  48  *
  49  * rl:          zfs_ratelimit_t struct
  50  */
  51 void
  52 zfs_ratelimit_fini(zfs_ratelimit_t *rl)
  53 {
  54         mutex_destroy(&rl->lock);
  55 }
  56
  57 /*
  58  * Re-implementation of the kernel's __ratelimit() function
  59  *
  60  * We had to write our own rate limiter because the kernel's __ratelimit()
  61  * function annoyingly prints out how many times it rate limited to the kernel
  62  * logs (and there's no way to turn it off):
  63  *
  64  *      __ratelimit: 59 callbacks suppressed
  65  *
  66  * If the kernel ever allows us to disable these prints, we should go back to
  67  * using __ratelimit() instead.
  68  *
  69  * Return values are the same as __ratelimit():
  70  *
  71  * 0: If we're rate limiting
  72  * 1: If we're not rate limiting.
  73  */
  74 int
  75 zfs_ratelimit(zfs_ratelimit_t *rl)
  76 {
  77         hrtime_t now;
  78
  79         hrtime_t elapsed;
  80         int error = 1;
  81
  82         mutex_enter(&rl->lock);
  83
  84         now = gethrtime();
  85         elapsed = now - rl->start;
  86
  87         rl->count++;
  88         if (NSEC2SEC(elapsed) >= rl->interval) {
  89                 rl->start = now;
  90                 rl->count = 0;
  91         } else {
  92                 if (rl->count >= rl->burst) {
  93                         error = 0; /* We're ratelimiting */
  94                 }
  95         }
  96         mutex_exit(&rl->lock);
  97
  98         return (error);
  99 }