FreeBSD/Linux Kernel Cross Reference
sys/sys/tim_filter.h

     #ifndef __tim_filter_h__
     #define __tim_filter_h__
     /*-
      * Copyright (c) 2016-9 Netflix, Inc.
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD$
     */
    /*
     * Author: Randall Stewart <rrs@netflix.com>
     */
    
    #include <sys/types.h>
    #include <machine/param.h>
    /* 
     * Do not change the size unless you know what you are
     * doing, the current size of 5 is designed around
     * the cache-line size for an amd64 processor. Other processors
     * may need other sizes.
     */
    #define NUM_FILTER_ENTRIES 3
    
    struct filter_entry {
            uint64_t value;         /* Value */
            uint32_t time_up;       /* Time updated */
    } __packed ;
    
    struct filter_entry_small {
            uint32_t value;         /* Value */
            uint32_t time_up;       /* Time updated */
    };
    
    struct time_filter {
            uint32_t cur_time_limit;
            struct filter_entry entries[NUM_FILTER_ENTRIES];
    #ifdef _KERNEL
    } __aligned(CACHE_LINE_SIZE);
    #else   
    };
    #endif
    struct time_filter_small {
            uint32_t cur_time_limit;
            struct filter_entry_small entries[NUM_FILTER_ENTRIES];
    };
    
    /*
     * To conserve on space there is a code duplication here (this
     * is where polymophism would be nice in the kernel). Everything
     * is duplicated to have a filter with a value of uint32_t instead
     * of a uint64_t. This saves 20 bytes and the structure size
     * drops to 44 from 64. The bad part about this is you end
     * up with two sets of functions. The xxx_small() access
     * the uint32_t value's where the xxx() the uint64_t values.
     * This forces the user to keep straight which type of structure
     * they allocated and which call they need to make. crossing
     * over calls will create either invalid memory references or
     * very bad results :)
     */
    
    #define FILTER_TYPE_MIN 1
    #define FILTER_TYPE_MAX 2
    
    #ifdef _KERNEL
    int setup_time_filter(struct time_filter *tf, int fil_type, uint32_t time_len);
    void reset_time(struct time_filter *tf, uint32_t time_len);
    void forward_filter_clock(struct time_filter *tf, uint32_t ticks_forward);
    void tick_filter_clock(struct time_filter *tf, uint32_t now);
    uint32_t apply_filter_min(struct time_filter *tf, uint64_t value, uint32_t now);
    uint32_t apply_filter_max(struct time_filter *tf, uint64_t value, uint32_t now);
    void filter_reduce_by(struct time_filter *tf, uint64_t reduce_by, uint32_t now);
    void filter_increase_by(struct time_filter *tf, uint64_t incr_by, uint32_t now);
    static uint64_t inline
    get_filter_value(struct time_filter *tf)
    {
            return(tf->entries[0].value);
    }
    
    static uint32_t inline
   get_cur_timelim(struct time_filter *tf)
   {
           return(tf->cur_time_limit);
   }
   
   int setup_time_filter_small(struct time_filter_small *tf,
                               int fil_type, uint32_t time_len);
   void reset_time_small(struct time_filter_small *tf, uint32_t time_len);
   void forward_filter_clock_small(struct time_filter_small *tf,
                                   uint32_t ticks_forward);
   void tick_filter_clock_small(struct time_filter_small *tf, uint32_t now);
   uint32_t apply_filter_min_small(struct time_filter_small *tf,
                                   uint32_t value, uint32_t now);
   uint32_t apply_filter_max_small(struct time_filter_small *tf,
                                   uint32_t value, uint32_t now);
   void filter_reduce_by_small(struct time_filter_small *tf,
                               uint32_t reduce_by, uint32_t now);
   void filter_increase_by_small(struct time_filter_small *tf,
                                 uint32_t incr_by, uint32_t now);
   static uint64_t inline
   get_filter_value_small(struct time_filter_small *tf)
   {
           return(tf->entries[0].value);
   }
   
   static uint32_t inline
   get_cur_timelim_small(struct time_filter_small *tf)
   {
           return(tf->cur_time_limit);
   }
   
   #endif
   #endif

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