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Diffstat (limited to '')
| -rw-r--r-- | net/netfilter/ipvs/ip_vs_twos.c | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/net/netfilter/ipvs/ip_vs_twos.c b/net/netfilter/ipvs/ip_vs_twos.c new file mode 100644 index 000000000000..acb55d8393ef --- /dev/null +++ b/net/netfilter/ipvs/ip_vs_twos.c @@ -0,0 +1,139 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* IPVS: Power of Twos Choice Scheduling module + * + * Authors: Darby Payne <darby.payne@applovin.com> + */ + +#define KMSG_COMPONENT "IPVS" +#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/random.h> + +#include <net/ip_vs.h> + +/* Power of Twos Choice scheduling, algorithm originally described by + * Michael Mitzenmacher. + * + * Randomly picks two destinations and picks the one with the least + * amount of connections + * + * The algorithm calculates a few variables + * - total_weight = sum of all weights + * - rweight1 = random number between [0,total_weight] + * - rweight2 = random number between [0,total_weight] + * + * For each destination + * decrement rweight1 and rweight2 by the destination weight + * pick choice1 when rweight1 is <= 0 + * pick choice2 when rweight2 is <= 0 + * + * Return choice2 if choice2 has less connections than choice 1 normalized + * by weight + * + * References + * ---------- + * + * [Mitzenmacher 2016] + * The Power of Two Random Choices: A Survey of Techniques and Results + * Michael Mitzenmacher, Andrea W. Richa y, Ramesh Sitaraman + * http://www.eecs.harvard.edu/~michaelm/NEWWORK/postscripts/twosurvey.pdf + * + */ +static struct ip_vs_dest *ip_vs_twos_schedule(struct ip_vs_service *svc, + const struct sk_buff *skb, + struct ip_vs_iphdr *iph) +{ + struct ip_vs_dest *dest, *choice1 = NULL, *choice2 = NULL; + int rweight1, rweight2, weight1 = -1, weight2 = -1, overhead1 = 0; + int overhead2, total_weight = 0, weight; + + IP_VS_DBG(6, "%s(): Scheduling...\n", __func__); + + /* Generate a random weight between [0,sum of all weights) */ + list_for_each_entry_rcu(dest, &svc->destinations, n_list) { + if (!(dest->flags & IP_VS_DEST_F_OVERLOAD)) { + weight = atomic_read(&dest->weight); + if (weight > 0) { + total_weight += weight; + choice1 = dest; + } + } + } + + if (!choice1) { + ip_vs_scheduler_err(svc, "no destination available"); + return NULL; + } + + /* Add 1 to total_weight so that the random weights are inclusive + * from 0 to total_weight + */ + total_weight += 1; + rweight1 = prandom_u32() % total_weight; + rweight2 = prandom_u32() % total_weight; + + /* Pick two weighted servers */ + list_for_each_entry_rcu(dest, &svc->destinations, n_list) { + if (dest->flags & IP_VS_DEST_F_OVERLOAD) + continue; + + weight = atomic_read(&dest->weight); + if (weight <= 0) + continue; + + rweight1 -= weight; + rweight2 -= weight; + + if (rweight1 <= 0 && weight1 == -1) { + choice1 = dest; + weight1 = weight; + overhead1 = ip_vs_dest_conn_overhead(dest); + } + + if (rweight2 <= 0 && weight2 == -1) { + choice2 = dest; + weight2 = weight; + overhead2 = ip_vs_dest_conn_overhead(dest); + } + + if (weight1 != -1 && weight2 != -1) + goto nextstage; + } + +nextstage: + if (choice2 && (weight2 * overhead1) > (weight1 * overhead2)) + choice1 = choice2; + + IP_VS_DBG_BUF(6, "twos: server %s:%u conns %d refcnt %d weight %d\n", + IP_VS_DBG_ADDR(choice1->af, &choice1->addr), + ntohs(choice1->port), atomic_read(&choice1->activeconns), + refcount_read(&choice1->refcnt), + atomic_read(&choice1->weight)); + + return choice1; +} + +static struct ip_vs_scheduler ip_vs_twos_scheduler = { + .name = "twos", + .refcnt = ATOMIC_INIT(0), + .module = THIS_MODULE, + .n_list = LIST_HEAD_INIT(ip_vs_twos_scheduler.n_list), + .schedule = ip_vs_twos_schedule, +}; + +static int __init ip_vs_twos_init(void) +{ + return register_ip_vs_scheduler(&ip_vs_twos_scheduler); +} + +static void __exit ip_vs_twos_cleanup(void) +{ + unregister_ip_vs_scheduler(&ip_vs_twos_scheduler); + synchronize_rcu(); +} + +module_init(ip_vs_twos_init); +module_exit(ip_vs_twos_cleanup); +MODULE_LICENSE("GPL"); |