120 lines
3.5 KiB
Diff
120 lines
3.5 KiB
Diff
Subject: mm, rt: kmap_atomic scheduling
|
|
From: Peter Zijlstra <peterz@infradead.org>
|
|
Date: Thu, 28 Jul 2011 10:43:51 +0200
|
|
|
|
In fact, with migrate_disable() existing one could play games with
|
|
kmap_atomic. You could save/restore the kmap_atomic slots on context
|
|
switch (if there are any in use of course), this should be esp easy now
|
|
that we have a kmap_atomic stack.
|
|
|
|
Something like the below.. it wants replacing all the preempt_disable()
|
|
stuff with pagefault_disable() && migrate_disable() of course, but then
|
|
you can flip kmaps around like below.
|
|
|
|
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
|
|
[dvhart@linux.intel.com: build fix]
|
|
Link: http://lkml.kernel.org/r/1311842631.5890.208.camel@twins
|
|
---
|
|
arch/x86/kernel/process_32.c | 36 ++++++++++++++++++++++++++++++++++++
|
|
include/linux/sched.h | 5 +++++
|
|
mm/memory.c | 2 ++
|
|
3 files changed, 43 insertions(+)
|
|
|
|
Index: linux-3.2/arch/x86/kernel/process_32.c
|
|
===================================================================
|
|
--- linux-3.2.orig/arch/x86/kernel/process_32.c
|
|
+++ linux-3.2/arch/x86/kernel/process_32.c
|
|
@@ -39,6 +39,7 @@
|
|
#include <linux/io.h>
|
|
#include <linux/kdebug.h>
|
|
#include <linux/cpuidle.h>
|
|
+#include <linux/highmem.h>
|
|
|
|
#include <asm/pgtable.h>
|
|
#include <asm/system.h>
|
|
@@ -350,6 +351,41 @@ __switch_to(struct task_struct *prev_p,
|
|
task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
|
|
__switch_to_xtra(prev_p, next_p, tss);
|
|
|
|
+#if defined CONFIG_PREEMPT_RT_FULL && defined CONFIG_HIGHMEM
|
|
+ /*
|
|
+ * Save @prev's kmap_atomic stack
|
|
+ */
|
|
+ prev_p->kmap_idx = __this_cpu_read(__kmap_atomic_idx);
|
|
+ if (unlikely(prev_p->kmap_idx)) {
|
|
+ int i;
|
|
+
|
|
+ for (i = 0; i < prev_p->kmap_idx; i++) {
|
|
+ int idx = i + KM_TYPE_NR * smp_processor_id();
|
|
+
|
|
+ pte_t *ptep = kmap_pte - idx;
|
|
+ prev_p->kmap_pte[i] = *ptep;
|
|
+ kpte_clear_flush(ptep, __fix_to_virt(FIX_KMAP_BEGIN + idx));
|
|
+ }
|
|
+
|
|
+ __this_cpu_write(__kmap_atomic_idx, 0);
|
|
+ }
|
|
+
|
|
+ /*
|
|
+ * Restore @next_p's kmap_atomic stack
|
|
+ */
|
|
+ if (unlikely(next_p->kmap_idx)) {
|
|
+ int i;
|
|
+
|
|
+ __this_cpu_write(__kmap_atomic_idx, next_p->kmap_idx);
|
|
+
|
|
+ for (i = 0; i < next_p->kmap_idx; i++) {
|
|
+ int idx = i + KM_TYPE_NR * smp_processor_id();
|
|
+
|
|
+ set_pte(kmap_pte - idx, next_p->kmap_pte[i]);
|
|
+ }
|
|
+ }
|
|
+#endif
|
|
+
|
|
/* If we're going to preload the fpu context, make sure clts
|
|
is run while we're batching the cpu state updates. */
|
|
if (preload_fpu)
|
|
Index: linux-3.2/include/linux/sched.h
|
|
===================================================================
|
|
--- linux-3.2.orig/include/linux/sched.h
|
|
+++ linux-3.2/include/linux/sched.h
|
|
@@ -63,6 +63,7 @@ struct sched_param {
|
|
#include <linux/nodemask.h>
|
|
#include <linux/mm_types.h>
|
|
|
|
+#include <asm/kmap_types.h>
|
|
#include <asm/system.h>
|
|
#include <asm/page.h>
|
|
#include <asm/ptrace.h>
|
|
@@ -1599,6 +1600,10 @@ struct task_struct {
|
|
struct rcu_head put_rcu;
|
|
int softirq_nestcnt;
|
|
#endif
|
|
+#if defined CONFIG_PREEMPT_RT_FULL && defined CONFIG_HIGHMEM
|
|
+ int kmap_idx;
|
|
+ pte_t kmap_pte[KM_TYPE_NR];
|
|
+#endif
|
|
};
|
|
|
|
#ifdef CONFIG_PREEMPT_RT_FULL
|
|
Index: linux-3.2/mm/memory.c
|
|
===================================================================
|
|
--- linux-3.2.orig/mm/memory.c
|
|
+++ linux-3.2/mm/memory.c
|
|
@@ -3439,6 +3439,7 @@ unlock:
|
|
#ifdef CONFIG_PREEMPT_RT_FULL
|
|
void pagefault_disable(void)
|
|
{
|
|
+ migrate_disable();
|
|
current->pagefault_disabled++;
|
|
/*
|
|
* make sure to have issued the store before a pagefault
|
|
@@ -3456,6 +3457,7 @@ void pagefault_enable(void)
|
|
*/
|
|
barrier();
|
|
current->pagefault_disabled--;
|
|
+ migrate_enable();
|
|
}
|
|
EXPORT_SYMBOL_GPL(pagefault_enable);
|
|
#endif
|