From 0f1a394ba68c4bbdedb1dbfdf6784ba54c07bbe4 Mon Sep 17 00:00:00 2001 From: Paul Mundt Date: Mon, 19 Nov 2007 13:05:18 +0900 Subject: [PATCH] sh: lockless UTLB miss fast-path. With the refactored update_mmu_cache() introduced in older kernels, there's no longer any need to take the page_table_lock in this path, so simply drop it completely. Without this, performance degradation is seen on SMP on heavily threaded workloads that don't use the split ptlock, and ultimately we have no reason to contend for the lock in the first place. Signed-off-by: Paul Mundt --- arch/sh/mm/fault.c | 25 +++++++------------------ 1 file changed, 7 insertions(+), 18 deletions(-) diff --git a/arch/sh/mm/fault.c b/arch/sh/mm/fault.c index c56a5fabcd0f..60d74f793a1d 100644 --- a/arch/sh/mm/fault.c +++ b/arch/sh/mm/fault.c @@ -258,9 +258,6 @@ asmlinkage int __kprobes __do_page_fault(struct pt_regs *regs, pmd_t *pmd; pte_t *pte; pte_t entry; - struct mm_struct *mm = current->mm; - spinlock_t *ptl = NULL; - int ret = 1; #ifdef CONFIG_SH_KGDB if (kgdb_nofault && kgdb_bus_err_hook) @@ -274,12 +271,11 @@ asmlinkage int __kprobes __do_page_fault(struct pt_regs *regs, */ if (address >= P3SEG && address < P3_ADDR_MAX) { pgd = pgd_offset_k(address); - mm = NULL; } else { - if (unlikely(address >= TASK_SIZE || !mm)) + if (unlikely(address >= TASK_SIZE || !current->mm)) return 1; - pgd = pgd_offset(mm, address); + pgd = pgd_offset(current->mm, address); } pud = pud_offset(pgd, address); @@ -289,16 +285,12 @@ asmlinkage int __kprobes __do_page_fault(struct pt_regs *regs, if (pmd_none_or_clear_bad(pmd)) return 1; - if (mm) - pte = pte_offset_map_lock(mm, pmd, address, &ptl); - else - pte = pte_offset_kernel(pmd, address); - + pte = pte_offset_kernel(pmd, address); entry = *pte; if (unlikely(pte_none(entry) || pte_not_present(entry))) - goto unlock; + return 1; if (unlikely(writeaccess && !pte_write(entry))) - goto unlock; + return 1; if (writeaccess) entry = pte_mkdirty(entry); @@ -306,9 +298,6 @@ asmlinkage int __kprobes __do_page_fault(struct pt_regs *regs, set_pte(pte, entry); update_mmu_cache(NULL, address, entry); - ret = 0; -unlock: - if (mm) - pte_unmap_unlock(pte, ptl); - return ret; + + return 0; }