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17cd01e4d1
W=1 builds warn on missing MODULE_DESCRIPTION, add them. Signed-off-by: Florian Westphal <fw@strlen.de> Acked-by: Julian Anastasov <ja@ssi.bg> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
140 lines
3.8 KiB
C
140 lines
3.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* IPVS: Power of Twos Choice Scheduling module
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*
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* Authors: Darby Payne <darby.payne@applovin.com>
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*/
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#define KMSG_COMPONENT "IPVS"
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#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/random.h>
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#include <net/ip_vs.h>
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/* Power of Twos Choice scheduling, algorithm originally described by
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* Michael Mitzenmacher.
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*
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* Randomly picks two destinations and picks the one with the least
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* amount of connections
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*
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* The algorithm calculates a few variables
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* - total_weight = sum of all weights
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* - rweight1 = random number between [0,total_weight]
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* - rweight2 = random number between [0,total_weight]
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*
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* For each destination
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* decrement rweight1 and rweight2 by the destination weight
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* pick choice1 when rweight1 is <= 0
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* pick choice2 when rweight2 is <= 0
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*
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* Return choice2 if choice2 has less connections than choice 1 normalized
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* by weight
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*
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* References
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* ----------
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*
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* [Mitzenmacher 2016]
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* The Power of Two Random Choices: A Survey of Techniques and Results
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* Michael Mitzenmacher, Andrea W. Richa y, Ramesh Sitaraman
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* http://www.eecs.harvard.edu/~michaelm/NEWWORK/postscripts/twosurvey.pdf
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*
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*/
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static struct ip_vs_dest *ip_vs_twos_schedule(struct ip_vs_service *svc,
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const struct sk_buff *skb,
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struct ip_vs_iphdr *iph)
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{
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struct ip_vs_dest *dest, *choice1 = NULL, *choice2 = NULL;
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int rweight1, rweight2, weight1 = -1, weight2 = -1, overhead1 = 0;
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int overhead2, total_weight = 0, weight;
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IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
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/* Generate a random weight between [0,sum of all weights) */
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list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
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if (!(dest->flags & IP_VS_DEST_F_OVERLOAD)) {
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weight = atomic_read(&dest->weight);
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if (weight > 0) {
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total_weight += weight;
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choice1 = dest;
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}
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}
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}
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if (!choice1) {
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ip_vs_scheduler_err(svc, "no destination available");
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return NULL;
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}
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/* Add 1 to total_weight so that the random weights are inclusive
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* from 0 to total_weight
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*/
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total_weight += 1;
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rweight1 = get_random_u32_below(total_weight);
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rweight2 = get_random_u32_below(total_weight);
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/* Pick two weighted servers */
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list_for_each_entry_rcu(dest, &svc->destinations, n_list) {
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if (dest->flags & IP_VS_DEST_F_OVERLOAD)
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continue;
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weight = atomic_read(&dest->weight);
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if (weight <= 0)
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continue;
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rweight1 -= weight;
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rweight2 -= weight;
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if (rweight1 <= 0 && weight1 == -1) {
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choice1 = dest;
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weight1 = weight;
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overhead1 = ip_vs_dest_conn_overhead(dest);
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}
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if (rweight2 <= 0 && weight2 == -1) {
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choice2 = dest;
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weight2 = weight;
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overhead2 = ip_vs_dest_conn_overhead(dest);
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}
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if (weight1 != -1 && weight2 != -1)
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goto nextstage;
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}
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nextstage:
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if (choice2 && (weight2 * overhead1) > (weight1 * overhead2))
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choice1 = choice2;
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IP_VS_DBG_BUF(6, "twos: server %s:%u conns %d refcnt %d weight %d\n",
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IP_VS_DBG_ADDR(choice1->af, &choice1->addr),
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ntohs(choice1->port), atomic_read(&choice1->activeconns),
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refcount_read(&choice1->refcnt),
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atomic_read(&choice1->weight));
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return choice1;
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}
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static struct ip_vs_scheduler ip_vs_twos_scheduler = {
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.name = "twos",
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.refcnt = ATOMIC_INIT(0),
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.module = THIS_MODULE,
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.n_list = LIST_HEAD_INIT(ip_vs_twos_scheduler.n_list),
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.schedule = ip_vs_twos_schedule,
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};
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static int __init ip_vs_twos_init(void)
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{
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return register_ip_vs_scheduler(&ip_vs_twos_scheduler);
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}
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static void __exit ip_vs_twos_cleanup(void)
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{
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unregister_ip_vs_scheduler(&ip_vs_twos_scheduler);
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synchronize_rcu();
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}
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module_init(ip_vs_twos_init);
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module_exit(ip_vs_twos_cleanup);
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("ipvs power of twos choice scheduler");
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