linux/arch/ia64/mm/tlb.c
de Dinechin, Christophe (Integrity VM) aec103bfa6 [IA64] Avoid unnecessary TLB flushes when allocating memory
Improve performance of memory allocations on ia64 by avoiding a global TLB
purge to purge a single page from the file cache. This happens whenever we
evict a page from the buffer cache to make room for some other allocation.

Test case: Run 'find /usr -type f | xargs cat > /dev/null' in the
background to fill the buffer cache, then run something that uses memory,
e.g. 'gmake -j50 install'. Instrumentation showed that the number of
global TLB purges went from a few millions down to about 170 over a 12
hours run of the above.

The performance impact is particularly noticeable under virtualization,
because a virtual TLB is generally both larger and slower to purge than
a physical one.

Signed-off-by: Christophe de Dinechin <ddd@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
2007-12-18 16:56:50 -08:00

209 lines
5.1 KiB
C

/*
* TLB support routines.
*
* Copyright (C) 1998-2001, 2003 Hewlett-Packard Co
* David Mosberger-Tang <davidm@hpl.hp.com>
*
* 08/02/00 A. Mallick <asit.k.mallick@intel.com>
* 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>
* Christophe de Dinechin <ddd@hp.com>: Avoid ptc.e on memory allocation
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#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 */
unsigned long max_bits; /* log2 of largest supported purge page-size */
} purge;
struct ia64_ctx ia64_ctx = {
.lock = __SPIN_LOCK_UNLOCKED(ia64_ctx.lock),
.next = 1,
.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)
{
int i, cpu;
unsigned long flush_bit;
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;
}
/* 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]
*/
cpu = get_cpu(); /* prevent preemption/migration */
for_each_online_cpu(i)
if (i != cpu)
per_cpu(ia64_need_tlb_flush, i) = 1;
put_cpu();
local_flush_tlb_all();
}
void
ia64_global_tlb_purge (struct mm_struct *mm, unsigned long start,
unsigned long end, unsigned long nbits)
{
static DEFINE_SPINLOCK(ptcg_lock);
struct mm_struct *active_mm = current->active_mm;
if (mm != active_mm) {
/* Restore region IDs for mm */
if (mm && active_mm) {
activate_context(mm);
} else {
flush_tlb_all();
return;
}
}
/* HW requires global serialization of ptc.ga. */
spin_lock(&ptcg_lock);
{
do {
/*
* Flush ALAT entries also.
*/
ia64_ptcga(start, (nbits<<2));
ia64_srlz_i();
start += (1UL << nbits);
} while (start < end);
}
spin_unlock(&ptcg_lock);
if (mm != active_mm) {
activate_context(active_mm);
}
}
void
local_flush_tlb_all (void)
{
unsigned long i, j, flags, count0, count1, stride0, stride1, addr;
addr = local_cpu_data->ptce_base;
count0 = local_cpu_data->ptce_count[0];
count1 = local_cpu_data->ptce_count[1];
stride0 = local_cpu_data->ptce_stride[0];
stride1 = local_cpu_data->ptce_stride[1];
local_irq_save(flags);
for (i = 0; i < count0; ++i) {
for (j = 0; j < count1; ++j) {
ia64_ptce(addr);
addr += stride1;
}
addr += stride0;
}
local_irq_restore(flags);
ia64_srlz_i(); /* srlz.i implies srlz.d */
}
void
flush_tlb_range (struct vm_area_struct *vma, unsigned long start,
unsigned long end)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long size = end - start;
unsigned long nbits;
#ifndef CONFIG_SMP
if (mm != current->active_mm) {
mm->context = 0;
return;
}
#endif
nbits = ia64_fls(size + 0xfff);
while (unlikely (((1UL << nbits) & purge.mask) == 0) &&
(nbits < purge.max_bits))
++nbits;
if (nbits > purge.max_bits)
nbits = purge.max_bits;
start &= ~((1UL << nbits) - 1);
preempt_disable();
#ifdef CONFIG_SMP
if (mm != current->active_mm || cpus_weight(mm->cpu_vm_mask) != 1) {
platform_global_tlb_purge(mm, start, end, nbits);
preempt_enable();
return;
}
#endif
do {
ia64_ptcl(start, (nbits<<2));
start += (1UL << nbits);
} while (start < end);
preempt_enable();
ia64_srlz_i(); /* srlz.i implies srlz.d */
}
EXPORT_SYMBOL(flush_tlb_range);
void __devinit
ia64_tlb_init (void)
{
ia64_ptce_info_t uninitialized_var(ptce_info); /* GCC be quiet */
unsigned long tr_pgbits;
long status;
if ((status = ia64_pal_vm_page_size(&tr_pgbits, &purge.mask)) != 0) {
printk(KERN_ERR "PAL_VM_PAGE_SIZE failed with status=%ld; "
"defaulting to architected purge page-sizes.\n", status);
purge.mask = 0x115557000UL;
}
purge.max_bits = ia64_fls(purge.mask);
ia64_get_ptce(&ptce_info);
local_cpu_data->ptce_base = ptce_info.base;
local_cpu_data->ptce_count[0] = ptce_info.count[0];
local_cpu_data->ptce_count[1] = ptce_info.count[1];
local_cpu_data->ptce_stride[0] = ptce_info.stride[0];
local_cpu_data->ptce_stride[1] = ptce_info.stride[1];
local_flush_tlb_all(); /* nuke left overs from bootstrapping... */
}