196 lines
6.2 KiB
Diff
196 lines
6.2 KiB
Diff
From 54051449030cb3c1642f9a6110316d3705eb3a23 Mon Sep 17 00:00:00 2001
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From: Andrew Zaborowski <andrew.zaborowski@intel.com>
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Date: Fri, 10 May 2024 18:57:34 -0700
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Subject: [PATCH 23/44] Track IRQ "slots" count per CPU to avoid overflowing
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There are situations where irqbalance may try to migrate large numbers of
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IRQs to a topo_obj, there's no upper bound on the number as the
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placement logic is based on load mainly. The kernel's irq bitmasks limit
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the number of IRQs on each cpu and if more are tried to be migrated, the
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write to smp_affinity returns -ENOSPC. This confuses irqbalance's
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logic, the topo_obj.interrupts list no longer matches the irqs actually
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on that CPU or cache domain, and results in floods of error messages.
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See https://github.com/Irqbalance/irqbalance/issues/303 for details.
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For an easy fix, track the number of IRQ slots still free on each CPU.
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We start with INT_MAX meaning "unknown" and when we first get a -ENOSPC,
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we know we have no slots left. From there update the slots count each
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time we migrate IRQs to/from the CPU core topo_obj. We may never see an
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-ENOSPC and in that case there's no change in current logic, we never
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start tracking.
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This way we don't need to know ahead of time how many slots the kernel
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has for each CPU. The number may be arch specific (it is about 200 on
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x86-64) and is dependent on the number managed IRQs kernel has
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registered, so we don't want to guess. This is also more tolerant to
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the topo_obj.interrupts lists not matching exactly the kernel's idea of
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each irq's current affinity, e.g. due to -EIO errors in the smp_affinity
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writes.
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For now only do the tracking at OBJ_TYPE_CPU level so we don't have to
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update slots_left for all parent objs.
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Th commit doesn't try to stop an ongoing activation of all the IRQs
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already scheduled for moving to one cpu, when that cpu starts returning
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ENOSPC. We'll still see a bunch of those errors in that iteration.
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But in subsequent calculate_placement() iterations we avoid assigning
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more IRQs to that cpu than we were able to successfully move before.
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---
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activate.c | 13 ++++++++++++-
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classify.c | 2 ++
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cputree.c | 10 ++++++++++
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irqbalance.c | 3 +++
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irqbalance.h | 1 +
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irqlist.c | 11 ++++++++++-
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placement.c | 3 +++
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types.h | 1 +
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8 files changed, 42 insertions(+), 2 deletions(-)
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diff --git a/activate.c b/activate.c
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index 0c1e7a1..10ad57d 100644
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--- a/activate.c
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+++ b/activate.c
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@@ -99,7 +99,6 @@ error:
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"Cannot change IRQ %i affinity: %s\n",
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info->irq, strerror(errsave));
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switch (errsave) {
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- case ENOSPC: /* Specified CPU APIC is full. */
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case EAGAIN: /* Interrupted by signal. */
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case EBUSY: /* Affinity change already in progress. */
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case EINVAL: /* IRQ would be bound to no CPU. */
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@@ -107,6 +106,18 @@ error:
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case ENOMEM: /* Kernel cannot allocate CPU mask. */
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/* Do not blacklist the IRQ on transient errors. */
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break;
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+ case ENOSPC: /* Specified CPU APIC is full. */
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+ if (info->assigned_obj->obj_type != OBJ_TYPE_CPU)
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+ break;
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+
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+ if (info->assigned_obj->slots_left > 0)
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+ info->assigned_obj->slots_left = -1;
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+ else
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+ /* Negative slots to count how many we need to free */
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+ info->assigned_obj->slots_left--;
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+
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+ force_rebalance_irq(info, NULL);
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+ break;
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default:
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/* Any other error is considered permanent. */
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info->level = BALANCE_NONE;
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diff --git a/classify.c b/classify.c
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index 08340db..69d72ac 100644
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--- a/classify.c
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+++ b/classify.c
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@@ -883,6 +883,8 @@ static void remove_no_existing_irq(struct irq_info *info, void *data __attribute
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entry = g_list_find_custom(info->assigned_obj->interrupts, info, compare_ints);
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if (entry) {
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info->assigned_obj->interrupts = g_list_delete_link(info->assigned_obj->interrupts, entry);
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+ /* Probe number of slots again, don't guess whether the IRQ left a free slot */
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+ info->assigned_obj->slots_left = INT_MAX;
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}
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}
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free_irq(info, NULL);
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diff --git a/cputree.c b/cputree.c
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index d66be55..6c7b3b4 100644
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--- a/cputree.c
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+++ b/cputree.c
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@@ -595,3 +595,13 @@ int get_cpu_count(void)
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return g_list_length(cpus);
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}
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+static void clear_obj_slots(struct topo_obj *d, void *data __attribute__((unused)))
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+{
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+ d->slots_left = INT_MAX;
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+ for_each_object(d->children, clear_obj_slots, NULL);
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+}
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+
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+void clear_slots(void)
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+{
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+ for_each_object(numa_nodes, clear_obj_slots, NULL);
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+}
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diff --git a/irqbalance.c b/irqbalance.c
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index 7efbc98..1490336 100644
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--- a/irqbalance.c
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+++ b/irqbalance.c
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@@ -298,6 +298,7 @@ gboolean scan(gpointer data __attribute__((unused)))
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} while (need_rebuild);
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for_each_irq(NULL, force_rebalance_irq, NULL);
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+ clear_slots();
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parse_proc_interrupts();
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parse_proc_stat();
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return TRUE;
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@@ -695,6 +696,8 @@ int main(int argc, char** argv)
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parse_proc_interrupts();
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parse_proc_stat();
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+ clear_slots();
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+
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#ifdef HAVE_IRQBALANCEUI
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if (init_socket()) {
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ret = EXIT_FAILURE;
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diff --git a/irqbalance.h b/irqbalance.h
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index 76640dd..47e40cc 100644
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--- a/irqbalance.h
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+++ b/irqbalance.h
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@@ -98,6 +98,7 @@ extern struct topo_obj *get_numa_node(int nodeid);
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#define cpu_numa_node(cpu) ((cpu)->parent->numa_nodes)
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extern struct topo_obj *find_cpu_core(int cpunr);
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extern int get_cpu_count(void);
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+extern void clear_slots(void);
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/*
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* irq db functions
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diff --git a/irqlist.c b/irqlist.c
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index 304b1c6..9483a11 100644
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--- a/irqlist.c
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+++ b/irqlist.c
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@@ -211,8 +211,17 @@ void migrate_irq_obj(struct topo_obj *from, struct topo_obj *to, struct irq_info
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migrate_irq(from_list, to_list, info);
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- if (to)
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+ if (from) {
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+ if (from->slots_left != INT_MAX)
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+ from->slots_left++;
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+ }
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+
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+ if (to) {
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+ if (to->slots_left != INT_MAX)
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+ to->slots_left--;
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+
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to->load += info->load + 1;
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+ }
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info->assigned_obj = to;
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}
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diff --git a/placement.c b/placement.c
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index f156e0e..3276dea 100644
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--- a/placement.c
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+++ b/placement.c
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@@ -59,6 +59,9 @@ static void find_best_object(struct topo_obj *d, void *data)
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if (d->powersave_mode)
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return;
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+ if (d->slots_left <= 0)
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+ return;
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+
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newload = d->load;
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if (newload < best->best_cost) {
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best->best = d;
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diff --git a/types.h b/types.h
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index ea1fae8..5c66bf9 100644
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--- a/types.h
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+++ b/types.h
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@@ -56,6 +56,7 @@ struct topo_obj {
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GList *children;
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GList *numa_nodes;
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GList **obj_type_list;
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+ int slots_left;
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};
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struct irq_info {
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--
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2.47.0
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