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[IA64] Use bitmaps for efficient context allocation/free

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Corrects the very inefficent method of finding free context_ids in
get_mmu_context().  Instead of walking the task_list of all processes,
2 bitmaps are used to efficently store and lookup state, inuse and
needs flushing. The entire rid address space is now used before calling
wrap_mmu_context and global tlb flushing.

Special thanks to Ken and Rohit for their review and modifications in
using a bit flushmap.

Signed-off-by: Peter Keilty <peter.keilty@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Peter Keilty 2005-10-31 16:44:47 -05:00 committed by Tony Luck
parent f2c84c0e84
commit dcc17d1bae
4 changed files with 44 additions and 33 deletions
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1
arch/ia64/kernel/setup.c
View File

@ -454,6 +454,7 @@ setup_arch (char **cmdline_p)
#endif
cpu_init(); /* initialize the bootstrap CPU */
mmu_context_init(); /* initialize context_id bitmap */
#ifdef CONFIG_ACPI
acpi_boot_init();

56
arch/ia64/mm/tlb.c
View File

@ -8,6 +8,8 @@
* Modified RID allocation for SMP
* Goutham Rao <goutham.rao@intel.com>
* IPI based ptc implementation and A-step IPI implementation.
* Rohit Seth <rohit.seth@intel.com>
* Ken Chen <kenneth.w.chen@intel.com>
*/
#include <linux/config.h>
#include <linux/module.h>
@ -16,12 +18,14 @@
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/mm.h>
#include <linux/bootmem.h>
#include <asm/delay.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>
#include <asm/pal.h>
#include <asm/tlbflush.h>
#include <asm/dma.h>
static struct {
unsigned long mask; /* mask of supported purge page-sizes */
@ -31,49 +35,43 @@ static struct {
struct ia64_ctx ia64_ctx = {
.lock = SPIN_LOCK_UNLOCKED,
.next = 1,
.limit = (1 << 15) - 1, /* start out with the safe (architected) limit */
.max_ctx = ~0U
};
DEFINE_PER_CPU(u8, ia64_need_tlb_flush);
/*
* Initializes the ia64_ctx.bitmap array based on max_ctx+1.
* Called after cpu_init() has setup ia64_ctx.max_ctx based on
* maximum RID that is supported by boot CPU.
*/
void __init
mmu_context_init (void)
{
ia64_ctx.bitmap = alloc_bootmem((ia64_ctx.max_ctx+1)>>3);
ia64_ctx.flushmap = alloc_bootmem((ia64_ctx.max_ctx+1)>>3);
}
/*
* Acquire the ia64_ctx.lock before calling this function!
*/
void
wrap_mmu_context (struct mm_struct *mm)
{
unsigned long tsk_context, max_ctx = ia64_ctx.max_ctx;
struct task_struct *tsk;
int i;
unsigned long flush_bit;
if (ia64_ctx.next > max_ctx)
ia64_ctx.next = 300; /* skip daemons */
ia64_ctx.limit = max_ctx + 1;
/*
* Scan all the task's mm->context and set proper safe range
*/
read_lock(&tasklist_lock);
repeat:
for_each_process(tsk) {
if (!tsk->mm)
continue;
tsk_context = tsk->mm->context;
if (tsk_context == ia64_ctx.next) {
if (++ia64_ctx.next >= ia64_ctx.limit) {
/* empty range: reset the range limit and start over */
if (ia64_ctx.next > max_ctx)
ia64_ctx.next = 300;
ia64_ctx.limit = max_ctx + 1;
goto repeat;
}
}
if ((tsk_context > ia64_ctx.next) && (tsk_context < ia64_ctx.limit))
ia64_ctx.limit = tsk_context;
for (i=0; i <= ia64_ctx.max_ctx / BITS_PER_LONG; i++) {
flush_bit = xchg(&ia64_ctx.flushmap[i], 0);
ia64_ctx.bitmap[i] ^= flush_bit;
}
read_unlock(&tasklist_lock);
/* use offset at 300 to skip daemons */
ia64_ctx.next = find_next_zero_bit(ia64_ctx.bitmap,
ia64_ctx.max_ctx, 300);
ia64_ctx.limit = find_next_bit(ia64_ctx.bitmap,
ia64_ctx.max_ctx, ia64_ctx.next);
/* can't call flush_tlb_all() here because of race condition with O(1) scheduler [EF] */
{
int cpu = get_cpu(); /* prevent preemption/migration */

19
include/asm-ia64/mmu_context.h
View File

@ -32,13 +32,17 @@
struct ia64_ctx {
spinlock_t lock;
unsigned int next; /* next context number to use */
unsigned int limit; /* next >= limit => must call wrap_mmu_context() */
unsigned int max_ctx; /* max. context value supported by all CPUs */
unsigned int limit; /* available free range */
unsigned int max_ctx; /* max. context value supported by all CPUs */
/* call wrap_mmu_context when next >= max */
unsigned long *bitmap; /* bitmap size is max_ctx+1 */
unsigned long *flushmap;/* pending rid to be flushed */
};
extern struct ia64_ctx ia64_ctx;
DECLARE_PER_CPU(u8, ia64_need_tlb_flush);
extern void mmu_context_init (void);
extern void wrap_mmu_context (struct mm_struct *mm);
static inline void
@ -83,9 +87,16 @@ get_mmu_context (struct mm_struct *mm)
context = mm->context;
if (context == 0) {
cpus_clear(mm->cpu_vm_mask);
if (ia64_ctx.next >= ia64_ctx.limit)
wrap_mmu_context(mm);
if (ia64_ctx.next >= ia64_ctx.limit) {
ia64_ctx.next = find_next_zero_bit(ia64_ctx.bitmap,
ia64_ctx.max_ctx, ia64_ctx.next);
ia64_ctx.limit = find_next_bit(ia64_ctx.bitmap,
ia64_ctx.max_ctx, ia64_ctx.next);
if (ia64_ctx.next >= ia64_ctx.max_ctx)
wrap_mmu_context(mm);
}
mm->context = context = ia64_ctx.next++;
__set_bit(context, ia64_ctx.bitmap);
}
}
spin_unlock_irqrestore(&ia64_ctx.lock, flags);

1
include/asm-ia64/tlbflush.h
View File

@ -51,6 +51,7 @@ flush_tlb_mm (struct mm_struct *mm)
if (!mm)
return;
set_bit(mm->context, ia64_ctx.flushmap);
mm->context = 0;
if (atomic_read(&mm->mm_users) == 0)