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Commit 7f0536f8 authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds
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uml: speed up page table walking 



The previous page table walking code was horribly inefficient.  This patch
replaces it with code taken from elsewhere in the kernel.

Forking from bash is now ~5% faster and page faults are handled ~10% faster.

Signed-off-by: default avatarJeff Dike <jdike@linux.intel.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f30c2c98

arch/um/kernel/tlb.c

+120 −82
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include "linux/mm.h"

#include "asm/page.h"

#include "asm/pgalloc.h"

#include "asm/pgtable.h"

#include "asm/tlbflush.h"

#include "choose-mode.h"

#include "mode_kern.h"
@@ -123,102 +124,139 @@ static int add_mprotect(unsigned long addr, unsigned long len, int r, int w, 


#define ADD_ROUND(n, inc) (((n) + (inc)) & ~((inc) - 1))



void fix_range_common(struct mm_struct *mm, unsigned long start_addr,

		      unsigned long end_addr, int force,

		      int (*do_ops)(union mm_context *, struct host_vm_op *,

				    int, int, void **))

static inline int update_pte_range(pmd_t *pmd, unsigned long addr,

				   unsigned long end, struct host_vm_op *ops,

				   int last_op, int *op_index, int force,

				   union mm_context *mmu, void **flush,

				   int (*do_ops)(union mm_context *,

						 struct host_vm_op *, int, int,

						 void **))

{

	pgd_t *npgd;

	pud_t *npud;

	pmd_t *npmd;

	pte_t *npte;

	union mm_context *mmu = &mm->context;

	unsigned long addr, end;

	int r, w, x;

	struct host_vm_op ops[1];

	void *flush = NULL;

	int op_index = -1, last_op = ARRAY_SIZE(ops) - 1;

	int ret = 0;



	if(mm == NULL)

		return;

	pte_t *pte;

	int r, w, x, ret = 0;



	ops[0].type = NONE;

	for(addr = start_addr; addr < end_addr && !ret;){

		npgd = pgd_offset(mm, addr);

		if(!pgd_present(*npgd)){

			end = ADD_ROUND(addr, PGDIR_SIZE);

			if(end > end_addr)

				end = end_addr;

			if(force || pgd_newpage(*npgd)){

				ret = add_munmap(addr, end - addr, ops,

						 &op_index, last_op, mmu,

						 &flush, do_ops);

				pgd_mkuptodate(*npgd);

	pte = pte_offset_kernel(pmd, addr);

	do {

		r = pte_read(*pte);

		w = pte_write(*pte);

		x = pte_exec(*pte);

		if (!pte_young(*pte)) {

			r = 0;

			w = 0;

		} else if (!pte_dirty(*pte)) {

			w = 0;

		}

			addr = end;

			continue;

		if(force || pte_newpage(*pte)){

			if(pte_present(*pte))

				ret = add_mmap(addr, pte_val(*pte) & PAGE_MASK,

					       PAGE_SIZE, r, w, x, ops,

					       op_index, last_op, mmu, flush,

					       do_ops);

			else ret = add_munmap(addr, PAGE_SIZE, ops, op_index,

					      last_op, mmu, flush, do_ops);

		}

		else if(pte_newprot(*pte))

			ret = add_mprotect(addr, PAGE_SIZE, r, w, x, ops,

					   op_index, last_op, mmu, flush,

					   do_ops);

		*pte = pte_mkuptodate(*pte);

	} while (pte++, addr += PAGE_SIZE, ((addr != end) && !ret));

	return ret;

}



		npud = pud_offset(npgd, addr);

		if(!pud_present(*npud)){

			end = ADD_ROUND(addr, PUD_SIZE);

			if(end > end_addr)

				end = end_addr;

			if(force || pud_newpage(*npud)){

				ret = add_munmap(addr, end - addr, ops,

						 &op_index, last_op, mmu,

						 &flush, do_ops);

				pud_mkuptodate(*npud);

static inline int update_pmd_range(pud_t *pud, unsigned long addr,

				   unsigned long end, struct host_vm_op *ops,

				   int last_op, int *op_index, int force,

				   union mm_context *mmu, void **flush,

				   int (*do_ops)(union mm_context *,

						 struct host_vm_op *, int, int,

						 void **))

{

	pmd_t *pmd;

	unsigned long next;

	int ret = 0;



	pmd = pmd_offset(pud, addr);

	do {

		next = pmd_addr_end(addr, end);

		if(!pmd_present(*pmd)){

			if(force || pmd_newpage(*pmd)){

				ret = add_munmap(addr, next - addr, ops,

						 op_index, last_op, mmu,

						 flush, do_ops);

				pmd_mkuptodate(*pmd);

			}

			addr = end;

			continue;

		}

		else ret = update_pte_range(pmd, addr, next, ops, last_op,

					    op_index, force, mmu, flush,

					    do_ops);

	} while (pmd++, addr = next, ((addr != end) && !ret));

	return ret;

}



		npmd = pmd_offset(npud, addr);

		if(!pmd_present(*npmd)){

			end = ADD_ROUND(addr, PMD_SIZE);

			if(end > end_addr)

				end = end_addr;

			if(force || pmd_newpage(*npmd)){

				ret = add_munmap(addr, end - addr, ops,

						 &op_index, last_op, mmu,

						 &flush, do_ops);

				pmd_mkuptodate(*npmd);

static inline int update_pud_range(pgd_t *pgd, unsigned long addr,

				   unsigned long end, struct host_vm_op *ops,

				   int last_op, int *op_index, int force,

				   union mm_context *mmu, void **flush,

				   int (*do_ops)(union mm_context *,

						 struct host_vm_op *, int, int,

						 void **))

{

	pud_t *pud;

	unsigned long next;

	int ret = 0;



	pud = pud_offset(pgd, addr);

	do {

		next = pud_addr_end(addr, end);

		if(!pud_present(*pud)){

			if(force || pud_newpage(*pud)){

				ret = add_munmap(addr, next - addr, ops,

						 op_index, last_op, mmu,

						 flush, do_ops);

				pud_mkuptodate(*pud);

			}

			addr = end;

			continue;

		}



		npte = pte_offset_kernel(npmd, addr);

		r = pte_read(*npte);

		w = pte_write(*npte);

		x = pte_exec(*npte);

		if (!pte_young(*npte)) {

			r = 0;

			w = 0;

		} else if (!pte_dirty(*npte)) {

			w = 0;

		else ret = update_pmd_range(pud, addr, next, ops, last_op,

					    op_index, force, mmu, flush,

					    do_ops);

	} while (pud++, addr = next, ((addr != end) && !ret));

	return ret;

}

		if(force || pte_newpage(*npte)){

			if(pte_present(*npte))

				ret = add_mmap(addr,

					       pte_val(*npte) & PAGE_MASK,

					       PAGE_SIZE, r, w, x, ops,

					       &op_index, last_op, mmu,

					       &flush, do_ops);

			else ret = add_munmap(addr, PAGE_SIZE, ops,



void fix_range_common(struct mm_struct *mm, unsigned long start_addr,

		      unsigned long end_addr, int force,

		      int (*do_ops)(union mm_context *, struct host_vm_op *,

				    int, int, void **))

{

	pgd_t *pgd;

	union mm_context *mmu = &mm->context;

	struct host_vm_op ops[1];

	unsigned long addr = start_addr, next;

	int ret = 0, last_op = ARRAY_SIZE(ops) - 1, op_index = -1;

	void *flush = NULL;

	unsigned long long start_time, end_time;



	start_time = os_nsecs();

	ops[0].type = NONE;

	pgd = pgd_offset(mm, addr);

	do {

		next = pgd_addr_end(addr, end_addr);

		if(!pgd_present(*pgd)){

			if (force || pgd_newpage(*pgd)){

				ret = add_munmap(addr, next - addr, ops,

						 &op_index, last_op, mmu,

						 &flush, do_ops);

				pgd_mkuptodate(*pgd);

			}

		else if(pte_newprot(*npte))

			ret = add_mprotect(addr, PAGE_SIZE, r, w, x, ops,

					   &op_index, last_op, mmu,

					   &flush, do_ops);



		*npte = pte_mkuptodate(*npte);

		addr += PAGE_SIZE;

		}

		else ret = update_pud_range(pgd, addr, next, ops, last_op,

					    &op_index, force, mmu, &flush,

					    do_ops);

	} while (pgd++, addr = next, ((addr != end_addr) && !ret));

	end_time = os_nsecs();

	log_info("total flush time - %Ld nsecs\n", end_time - start_time);



	if(!ret)

		ret = (*do_ops)(mmu, ops, op_index, 1, &flush);