![Thomas Gleixner](/assets/img/avatar_default.png)
Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
266 lines
6.8 KiB
C
266 lines
6.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* IPVS: Weighted Round-Robin Scheduling module
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*
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* Authors: Wensong Zhang <wensong@linuxvirtualserver.org>
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*
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* Changes:
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* Wensong Zhang : changed the ip_vs_wrr_schedule to return dest
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* Wensong Zhang : changed some comestics things for debugging
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* Wensong Zhang : changed for the d-linked destination list
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* Wensong Zhang : added the ip_vs_wrr_update_svc
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* Julian Anastasov : fixed the bug of returning destination
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* with weight 0 when all weights are zero
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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/module.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/net.h>
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#include <linux/gcd.h>
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#include <net/ip_vs.h>
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/* The WRR algorithm depends on some caclulations:
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* - mw: maximum weight
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* - di: weight step, greatest common divisor from all weights
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* - cw: current required weight
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* As result, all weights are in the [di..mw] range with a step=di.
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*
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* First, we start with cw = mw and select dests with weight >= cw.
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* Then cw is reduced with di and all dests are checked again.
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* Last pass should be with cw = di. We have mw/di passes in total:
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*
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* pass 1: cw = max weight
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* pass 2: cw = max weight - di
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* pass 3: cw = max weight - 2 * di
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* ...
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* last pass: cw = di
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*
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* Weights are supposed to be >= di but we run in parallel with
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* weight changes, it is possible some dest weight to be reduced
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* below di, bad if it is the only available dest.
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*
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* So, we modify how mw is calculated, now it is reduced with (di - 1),
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* so that last cw is 1 to catch such dests with weight below di:
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* pass 1: cw = max weight - (di - 1)
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* pass 2: cw = max weight - di - (di - 1)
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* pass 3: cw = max weight - 2 * di - (di - 1)
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* ...
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* last pass: cw = 1
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*
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*/
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/*
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* current destination pointer for weighted round-robin scheduling
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*/
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struct ip_vs_wrr_mark {
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struct ip_vs_dest *cl; /* current dest or head */
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int cw; /* current weight */
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int mw; /* maximum weight */
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int di; /* decreasing interval */
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struct rcu_head rcu_head;
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};
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static int ip_vs_wrr_gcd_weight(struct ip_vs_service *svc)
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{
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struct ip_vs_dest *dest;
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int weight;
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int g = 0;
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list_for_each_entry(dest, &svc->destinations, n_list) {
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weight = atomic_read(&dest->weight);
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if (weight > 0) {
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if (g > 0)
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g = gcd(weight, g);
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else
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g = weight;
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}
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}
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return g ? g : 1;
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}
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/*
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* Get the maximum weight of the service destinations.
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*/
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static int ip_vs_wrr_max_weight(struct ip_vs_service *svc)
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{
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struct ip_vs_dest *dest;
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int new_weight, weight = 0;
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list_for_each_entry(dest, &svc->destinations, n_list) {
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new_weight = atomic_read(&dest->weight);
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if (new_weight > weight)
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weight = new_weight;
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}
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return weight;
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}
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static int ip_vs_wrr_init_svc(struct ip_vs_service *svc)
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{
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struct ip_vs_wrr_mark *mark;
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/*
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* Allocate the mark variable for WRR scheduling
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*/
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mark = kmalloc(sizeof(struct ip_vs_wrr_mark), GFP_KERNEL);
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if (mark == NULL)
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return -ENOMEM;
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mark->cl = list_entry(&svc->destinations, struct ip_vs_dest, n_list);
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mark->di = ip_vs_wrr_gcd_weight(svc);
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mark->mw = ip_vs_wrr_max_weight(svc) - (mark->di - 1);
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mark->cw = mark->mw;
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svc->sched_data = mark;
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return 0;
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}
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static void ip_vs_wrr_done_svc(struct ip_vs_service *svc)
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{
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struct ip_vs_wrr_mark *mark = svc->sched_data;
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/*
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* Release the mark variable
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*/
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kfree_rcu(mark, rcu_head);
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}
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static int ip_vs_wrr_dest_changed(struct ip_vs_service *svc,
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struct ip_vs_dest *dest)
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{
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struct ip_vs_wrr_mark *mark = svc->sched_data;
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spin_lock_bh(&svc->sched_lock);
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mark->cl = list_entry(&svc->destinations, struct ip_vs_dest, n_list);
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mark->di = ip_vs_wrr_gcd_weight(svc);
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mark->mw = ip_vs_wrr_max_weight(svc) - (mark->di - 1);
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if (mark->cw > mark->mw || !mark->cw)
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mark->cw = mark->mw;
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else if (mark->di > 1)
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mark->cw = (mark->cw / mark->di) * mark->di + 1;
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spin_unlock_bh(&svc->sched_lock);
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return 0;
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}
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/*
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* Weighted Round-Robin Scheduling
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*/
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static struct ip_vs_dest *
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ip_vs_wrr_schedule(struct ip_vs_service *svc, 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, *last, *stop = NULL;
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struct ip_vs_wrr_mark *mark = svc->sched_data;
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bool last_pass = false, restarted = false;
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IP_VS_DBG(6, "%s(): Scheduling...\n", __func__);
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spin_lock_bh(&svc->sched_lock);
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dest = mark->cl;
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/* No available dests? */
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if (mark->mw == 0)
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goto err_noavail;
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last = dest;
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/* Stop only after all dests were checked for weight >= 1 (last pass) */
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while (1) {
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list_for_each_entry_continue_rcu(dest,
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&svc->destinations,
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n_list) {
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if (!(dest->flags & IP_VS_DEST_F_OVERLOAD) &&
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atomic_read(&dest->weight) >= mark->cw)
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goto found;
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if (dest == stop)
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goto err_over;
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}
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mark->cw -= mark->di;
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if (mark->cw <= 0) {
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mark->cw = mark->mw;
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/* Stop if we tried last pass from first dest:
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* 1. last_pass: we started checks when cw > di but
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* then all dests were checked for w >= 1
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* 2. last was head: the first and only traversal
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* was for weight >= 1, for all dests.
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*/
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if (last_pass ||
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&last->n_list == &svc->destinations)
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goto err_over;
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restarted = true;
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}
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last_pass = mark->cw <= mark->di;
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if (last_pass && restarted &&
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&last->n_list != &svc->destinations) {
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/* First traversal was for w >= 1 but only
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* for dests after 'last', now do the same
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* for all dests up to 'last'.
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*/
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stop = last;
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}
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}
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found:
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IP_VS_DBG_BUF(6, "WRR: server %s:%u "
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"activeconns %d refcnt %d weight %d\n",
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IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port),
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atomic_read(&dest->activeconns),
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refcount_read(&dest->refcnt),
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atomic_read(&dest->weight));
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mark->cl = dest;
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out:
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spin_unlock_bh(&svc->sched_lock);
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return dest;
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err_noavail:
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mark->cl = dest;
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dest = NULL;
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ip_vs_scheduler_err(svc, "no destination available");
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goto out;
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err_over:
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mark->cl = dest;
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dest = NULL;
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ip_vs_scheduler_err(svc, "no destination available: "
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"all destinations are overloaded");
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goto out;
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}
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static struct ip_vs_scheduler ip_vs_wrr_scheduler = {
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.name = "wrr",
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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_wrr_scheduler.n_list),
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.init_service = ip_vs_wrr_init_svc,
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.done_service = ip_vs_wrr_done_svc,
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.add_dest = ip_vs_wrr_dest_changed,
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.del_dest = ip_vs_wrr_dest_changed,
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.upd_dest = ip_vs_wrr_dest_changed,
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.schedule = ip_vs_wrr_schedule,
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};
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static int __init ip_vs_wrr_init(void)
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{
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return register_ip_vs_scheduler(&ip_vs_wrr_scheduler) ;
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}
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static void __exit ip_vs_wrr_cleanup(void)
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{
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unregister_ip_vs_scheduler(&ip_vs_wrr_scheduler);
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synchronize_rcu();
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}
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module_init(ip_vs_wrr_init);
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module_exit(ip_vs_wrr_cleanup);
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MODULE_LICENSE("GPL");
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