Re: Extensible hashing and RCU

[Evgeniy Polyakov]

On Tue, Feb 20, 2007 at 07:59:07PM +0300, Evgeniy Polyakov ([EMAIL PROTECTED]) 
wrote:
> I've attached source code and running script.
> $ ./run.sh

Yep, of course.

-- 
        Evgeniy Polyakov

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <time.h>

#include <arpa/inet.h>

typedef unsigned int u32;
typedef unsigned short u16;
typedef unsigned char u8;

typedef unsigned int __u32;
typedef unsigned short __u16;
typedef unsigned char __u8;

#include "jhash.h"

struct hash_entry
{
        unsigned long           counter;
};

static inline __u32 num2ip(__u8 a1, __u8 a2, __u8 a3, __u8 a4)
{
        __u32 a = 0;

        a |= a1;
        a <<= 8;
        a |= a2;
        a <<= 8;
        a |= a3;
        a <<= 8;
        a |= a4;

        return a;
}

static inline __u8 get_random_byte(void)
{
        return 1 + (int) (255.0 * (rand() / (RAND_MAX + 1.0)));
}

static inline __u16 get_random_word(void)
{
        return 1 + (int) (65536.0 * (rand() / (RAND_MAX + 1.0)));
}

unsigned int hash_addr1(__u32 faddr, __u16 fport, __u32 laddr, __u16 lport)
{
        unsigned int h = (laddr ^ lport) ^ (faddr ^ fport);
        h ^= h >> 16;
        h ^= h >> 8;
        return h;
}

unsigned int hash_addr(__u32 faddr, __u16 fport, __u32 laddr, __u16 lport)
{
        u32 ports;
        unsigned int h;

        ports = lport;
        ports <<= 16;
        ports |= fport;

        h = jhash_3words(faddr, laddr, ports, 123123);
#ifdef HASH_FOLD
        h ^= h >> 16;
        h ^= h >> 8;
#endif
        return h;
}

int main()
{
        struct hash_entry *table;
        __u32 saddr, daddr;
        __u16 sport, dport;
        unsigned int hash, i, *results;
        unsigned int hash_size = (1<<10), iter_num = 100;

        table = malloc(hash_size * sizeof(struct hash_entry));
        if (!table)
                return -ENOMEM;
        
        results = malloc(hash_size * sizeof(unsigned int));
        if (!results)
                return -ENOMEM;

        for (i=0; i<hash_size; ++i) {
                results[i] = 0;
                table[i].counter = 0;
        }

        srand(time(NULL));

        daddr = num2ip(192, 168, 0, 1);
        dport = htons(80);
        saddr = num2ip(192, 168, 0, 2);
        saddr = num2ip(get_random_byte(), get_random_byte(), get_random_byte(), 
get_random_byte());
        sport = ntohs(10000);
        
        for (i=0; i<hash_size*iter_num; ++i) {
                //sport++;
                sport = get_random_word();

#ifdef USE_XOR
                hash = hash_addr1(saddr, ntohs(sport), daddr, dport);
#else
                hash = hash_addr(saddr, ntohs(sport), daddr, dport);
#endif
                hash &= (hash_size - 1);

                table[hash].counter++;
        }

        for (i=0; i<hash_size; ++i)
                results[table[i].counter]++;
        
        for (i=1; i<hash_size; ++i)
                printf("%u %u\n", i, results[i]);
                //printf("%u %lu\n", i, table[i].counter);
        
        return 0;
}

run.sh
Description: Bourne shell script

artefact.png
Description: PNG image

distribution.png
Description: PNG image