Re: [GIT PULL] scheduler fixes

Pekka J Enberg
2009-05-24T16:13:59Z

On Mon, 18 May 2009, Linus Torvalds wrote:
> > > I hate that stupid bootmem allocator. I suspect we seriously
> > > over-use it, and that we _should_ be able to do the SL*B init
> > > earlier.
> >
> > Hm, tempting thought - not sure how to pull it off though.
>
> As far as I can recall, one of the things that historically made us want
> to use the bootmem allocator even relatively late was that the real SLAB
> allocator had to wait until all the node information etc was initialized.
>
> That's pretty damn late. And I wonder if SLUB (and SLOB) might not need a
> lot less initialization, and work much earlier. Something like that might
> be the final nail in the coffin for SLAB, and convince me to just say
> 'we don't support it any more".

Ingo, here's a patch that boots UMA+SMP+SLUB x86-64 kernel on qemu all
the way to userspace. It probably breaks bunch of things for now but
something for you to play with if you want.

Pekka

diff --git a/init/main.c b/init/main.c
index 3bbf93b..856afa9 100644
--- a/init/main.c
+++ b/init/main.c
@@ -575,6 +575,22 @@ asmlinkage void __init start_kernel(void)
setup_nr_cpu_ids();
smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */

+ build_all_zonelists();
+ page_alloc_init();
+
+ printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
+ parse_early_param();
+ parse_args("Booting kernel", static_command_line, __start___param,
+ __stop___param - __start___param,
+ &unknown_bootoption);
+ /*
+ * Setup kernel memory allocators
+ */
+ pidhash_init();
+ vmalloc_init();
+ vfs_caches_init_early();
+ mem_init();
+ kmem_cache_init();
/*
* Set up the scheduler prior starting any interrupts (such as the
* timer interrupt). Full topology setup happens at smp_init()
@@ -586,13 +602,6 @@ asmlinkage void __init start_kernel(void)
* fragile until we cpu_idle() for the first time.
*/
preempt_disable();
- build_all_zonelists();
- page_alloc_init();
- printk(KERN_NOTICE "Kernel command line: %s\n", boot_command_line);
- parse_early_param();
- parse_args("Booting kernel", static_command_line, __start___param,
- __stop___param - __start___param,
- &unknown_bootoption);
if (!irqs_disabled()) {
printk(KERN_WARNING "start_kernel(): bug: interrupts were "
"enabled *very* early, fixing it\n");
@@ -604,7 +613,6 @@ asmlinkage void __init start_kernel(void)
/* init some links before init_ISA_irqs() */
early_irq_init();
init_IRQ();
- pidhash_init();
init_timers();
hrtimers_init();
softirq_init();
@@ -646,14 +654,10 @@ asmlinkage void __init start_kernel(void)
initrd_start = 0;
}
#endif
- vmalloc_init();
- vfs_caches_init_early();
cpuset_init_early();
page_cgroup_init();
- mem_init();
enable_debug_pagealloc();
cpu_hotplug_init();
- kmem_cache_init();
kmemtrace_init();
debug_objects_mem_init();
idr_init_cache();
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 26e0875..702a696 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -18,7 +18,7 @@
#include <linux/rculist.h>
#include <linux/hash.h>
#include <trace/irq.h>
-#include <linux/bootmem.h>
+#include <linux/slab.h>

#include "internals.h"

@@ -44,7 +44,7 @@ void handle_bad_irq(unsigned int irq, struct irq_desc *desc)
#if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_HARDIRQS)
static void __init init_irq_default_affinity(void)
{
- alloc_bootmem_cpumask_var(&irq_default_affinity);
+ alloc_cpumask_var(&irq_default_affinity, GFP_NOWAIT);
cpumask_setall(irq_default_affinity);
}
#else
@@ -158,12 +158,12 @@ int __init early_irq_init(void)
legacy_count = ARRAY_SIZE(irq_desc_legacy);

/* allocate irq_desc_ptrs array based on nr_irqs */
- irq_desc_ptrs = alloc_bootmem(nr_irqs * sizeof(void *));
+ irq_desc_ptrs = kcalloc(nr_irqs, sizeof(void *), GFP_NOWAIT);

/* allocate based on nr_cpu_ids */
/* FIXME: invert kstat_irgs, and it'd be a per_cpu_alloc'd thing */
- kstat_irqs_legacy = alloc_bootmem(NR_IRQS_LEGACY * nr_cpu_ids *
- sizeof(int));
+ kstat_irqs_legacy = kzalloc(NR_IRQS_LEGACY * nr_cpu_ids *
+ sizeof(int), GFP_NOWAIT);

for (i = 0; i < legacy_count; i++) {
desc[i].irq = i;
diff --git a/kernel/sched.c b/kernel/sched.c
index 26efa47..b403536 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -68,7 +68,6 @@
#include <linux/pagemap.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
-#include <linux/bootmem.h>
#include <linux/debugfs.h>
#include <linux/ctype.h>
#include <linux/ftrace.h>
@@ -7525,21 +7524,18 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd)

static int __init_refok init_rootdomain(struct root_domain *rd, bool bootmem)
{
+ gfp_t gfp = GFP_KERNEL;
+
memset(rd, 0, sizeof(*rd));

- if (bootmem) {
- alloc_bootmem_cpumask_var(&def_root_domain.span);
- alloc_bootmem_cpumask_var(&def_root_domain.online);
- alloc_bootmem_cpumask_var(&def_root_domain.rto_mask);
- cpupri_init(&rd->cpupri, true);
- return 0;
- }
+ if (bootmem)
+ gfp = GFP_NOWAIT;

- if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))
+ if (!alloc_cpumask_var(&rd->span, gfp))
goto out;
- if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
+ if (!alloc_cpumask_var(&rd->online, gfp))
goto free_span;
- if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
+ if (!alloc_cpumask_var(&rd->rto_mask, gfp))
goto free_online;

if (cpupri_init(&rd->cpupri, false) != 0)
@@ -8860,12 +8856,8 @@ void __init sched_init(void)
#ifdef CONFIG_CPUMASK_OFFSTACK
alloc_size += num_possible_cpus() * cpumask_size();
#endif
- /*
- * As sched_init() is called before page_alloc is setup,
- * we use alloc_bootmem().
- */
if (alloc_size) {
- ptr = (unsigned long)alloc_bootmem(alloc_size);
+ ptr = (unsigned long) kzalloc(alloc_size, GFP_NOWAIT);

#ifdef CONFIG_FAIR_GROUP_SCHED
init_task_group.se = (struct sched_entity **)ptr;
@@ -9051,12 +9043,12 @@ void __init sched_init(void)
current->sched_class = &fair_sched_class;

/* Allocate the nohz_cpu_mask if CONFIG_CPUMASK_OFFSTACK */
- alloc_bootmem_cpumask_var(&nohz_cpu_mask);
+ alloc_cpumask_var(&nohz_cpu_mask, GFP_NOWAIT);
#ifdef CONFIG_SMP
#ifdef CONFIG_NO_HZ
- alloc_bootmem_cpumask_var(&nohz.cpu_mask);
+ alloc_cpumask_var(&nohz.cpu_mask, GFP_NOWAIT);
#endif
- alloc_bootmem_cpumask_var(&cpu_isolated_map);
+ alloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
#endif /* SMP */

scheduler_running = 1;
diff --git a/mm/slub.c b/mm/slub.c
index 65ffda5..0ead807 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2557,13 +2557,16 @@ static struct kmem_cache *create_kmalloc_cache(struct kmem_cache *s,
if (gfp_flags & SLUB_DMA)
flags = SLAB_CACHE_DMA;

- down_write(&slub_lock);
+ /*
+ * This function is called with IRQs disabled during early-boot on
+ * single CPU so there's no need to take slub_lock here.
+ */
if (!kmem_cache_open(s, gfp_flags, name, size, ARCH_KMALLOC_MINALIGN,
flags, NULL))
goto panic;

list_add(&s->list, &slab_caches);
- up_write(&slub_lock);
+
if (sysfs_slab_add(s))
goto panic;
return s;
@@ -3021,7 +3024,7 @@ void __init kmem_cache_init(void)
* kmem_cache_open for slab_state == DOWN.
*/
create_kmalloc_cache(&kmalloc_caches[0], "kmem_cache_node",
- sizeof(struct kmem_cache_node), GFP_KERNEL);
+ sizeof(struct kmem_cache_node), GFP_NOWAIT);
kmalloc_caches[0].refcount = -1;
caches++;

@@ -3034,16 +3037,16 @@ void __init kmem_cache_init(void)
/* Caches that are not of the two-to-the-power-of size */
if (KMALLOC_MIN_SIZE <= 64) {
create_kmalloc_cache(&kmalloc_caches[1],
- "kmalloc-96", 96, GFP_KERNEL);
+ "kmalloc-96", 96, GFP_NOWAIT);
caches++;
create_kmalloc_cache(&kmalloc_caches[2],
- "kmalloc-192", 192, GFP_KERNEL);
+ "kmalloc-192", 192, GFP_NOWAIT);
caches++;
}

for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++) {
create_kmalloc_cache(&kmalloc_caches[i],
- "kmalloc", 1 << i, GFP_KERNEL);
+ "kmalloc", 1 << i, GFP_NOWAIT);
caches++;
}

@@ -3080,7 +3083,7 @@ void __init kmem_cache_init(void)
/* Provide the correct kmalloc names now that the caches are up */
for (i = KMALLOC_SHIFT_LOW; i < SLUB_PAGE_SHIFT; i++)
kmalloc_caches[i]. name =
- kasprintf(GFP_KERNEL, "kmalloc-%d", 1 << i);
+ kasprintf(GFP_NOWAIT, "kmalloc-%d", 1 << i);

#ifdef CONFIG_SMP
register_cpu_notifier(&slab_notifier);