FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/zfs/zfs_ratelimit.c

     /*
      * CDDL HEADER START
      *
      * The contents of this file are subject to the terms of the
      * Common Development and Distribution License (the "License").
      * You may not use this file except in compliance with the License.
      *
      * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      * or https://opensource.org/licenses/CDDL-1.0.
     * See the License for the specific language governing permissions
     * and limitations under the License.
     *
     * When distributing Covered Code, include this CDDL HEADER in each
     * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     * If applicable, add the following below this CDDL HEADER, with the
     * fields enclosed by brackets "[]" replaced with your own identifying
     * information: Portions Copyright [yyyy] [name of copyright owner]
     *
     * CDDL HEADER END
     */
    
    /*
     * Copyright (c) 2017, Lawrence Livermore National Security, LLC.
     */
    
    #include <sys/zfs_ratelimit.h>
    
    /*
     * Initialize rate limit struct
     *
     * rl:          zfs_ratelimit_t struct
     * burst:       Number to allow in an interval before rate limiting
     * interval:    Interval time in seconds
     */
    void
    zfs_ratelimit_init(zfs_ratelimit_t *rl, unsigned int *burst,
        unsigned int interval)
    {
            rl->count = 0;
            rl->start = 0;
            rl->interval = interval;
            rl->burst = burst;
            mutex_init(&rl->lock, NULL, MUTEX_DEFAULT, NULL);
    }
    
    /*
     * Finalize rate limit struct
     *
     * rl:          zfs_ratelimit_t struct
     */
    void
    zfs_ratelimit_fini(zfs_ratelimit_t *rl)
    {
            mutex_destroy(&rl->lock);
    }
    
    /*
     * Re-implementation of the kernel's __ratelimit() function
     *
     * We had to write our own rate limiter because the kernel's __ratelimit()
     * function annoyingly prints out how many times it rate limited to the kernel
     * logs (and there's no way to turn it off):
     *
     *      __ratelimit: 59 callbacks suppressed
     *
     * If the kernel ever allows us to disable these prints, we should go back to
     * using __ratelimit() instead.
     *
     * Return values are the same as __ratelimit():
     *
     * 0: If we're rate limiting
     * 1: If we're not rate limiting.
     */
    int
    zfs_ratelimit(zfs_ratelimit_t *rl)
    {
            hrtime_t now;
    
            hrtime_t elapsed;
            int error = 1;
    
            mutex_enter(&rl->lock);
    
            now = gethrtime();
            elapsed = now - rl->start;
    
            rl->count++;
            if (NSEC2SEC(elapsed) >= rl->interval) {
                    rl->start = now;
                    rl->count = 0;
            } else {
                    if (rl->count >= *rl->burst) {
                            error = 0; /* We're ratelimiting */
                    }
            }
            mutex_exit(&rl->lock);
    
            return (error);
    }

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