Hello, On Wed, 6 Jan 2021, dpayne wrote: > Adds the random twos choice load-balancing algorithm. The algorithm will > pick two random servers based on weights. Then select the server with > the least amount of connections normalized by weight. The algorithm > avoids the "herd behavior" problem. The algorithm comes from a paper > by Michael Mitzenmacher available here > http://www.eecs.harvard.edu/~michaelm/NEWWORK/postscripts/twosurvey.pdf > > Signed-off-by: dpayne <darby.payne@xxxxxxxxx> Looks good to me for -next, thanks! Acked-by: Julian Anastasov <ja@xxxxxx> > --- > net/netfilter/ipvs/Kconfig | 11 +++ > net/netfilter/ipvs/Makefile | 1 + > net/netfilter/ipvs/ip_vs_twos.c | 139 ++++++++++++++++++++++++++++++++ > 3 files changed, 151 insertions(+) > create mode 100644 net/netfilter/ipvs/ip_vs_twos.c > > diff --git a/net/netfilter/ipvs/Kconfig b/net/netfilter/ipvs/Kconfig > index eb0e329f9b8d..8ca542a759d4 100644 > --- a/net/netfilter/ipvs/Kconfig > +++ b/net/netfilter/ipvs/Kconfig > @@ -271,6 +271,17 @@ config IP_VS_NQ > If you want to compile it in kernel, say Y. To compile it as a > module, choose M here. If unsure, say N. > > +config IP_VS_TWOS > + tristate "weighted random twos choice least-connection scheduling" > + help > + The weighted random twos choice least-connection scheduling > + algorithm picks two random real servers and directs network > + connections to the server with the least active connections > + normalized by the server weight. > + > + If you want to compile it in kernel, say Y. To compile it as a > + module, choose M here. If unsure, say N. > + > comment 'IPVS SH scheduler' > > config IP_VS_SH_TAB_BITS > diff --git a/net/netfilter/ipvs/Makefile b/net/netfilter/ipvs/Makefile > index bfce2677fda2..bb5d8125c82a 100644 > --- a/net/netfilter/ipvs/Makefile > +++ b/net/netfilter/ipvs/Makefile > @@ -36,6 +36,7 @@ obj-$(CONFIG_IP_VS_SH) += ip_vs_sh.o > obj-$(CONFIG_IP_VS_MH) += ip_vs_mh.o > obj-$(CONFIG_IP_VS_SED) += ip_vs_sed.o > obj-$(CONFIG_IP_VS_NQ) += ip_vs_nq.o > +obj-$(CONFIG_IP_VS_TWOS) += ip_vs_twos.o > > # IPVS application helpers > obj-$(CONFIG_IP_VS_FTP) += ip_vs_ftp.o > 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@xxxxxxxxxxxx> > + */ > + > +#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"); > -- > 2.29.2 Regards -- Julian Anastasov <ja@xxxxxx>
