From 3df3212f9722c7e45c723b9ea231a04ba4dbc47c Mon Sep 17 00:00:00 2001 From: Alex Shi Date: Thu, 28 Jun 2012 09:02:20 +0800 Subject: [PATCH] x86/tlb: add tlb_flushall_shift knob into debugfs kernel will replace cr3 rewrite with invlpg when tlb_flush_entries <= active_tlb_entries / 2^tlb_flushall_factor if tlb_flushall_factor is -1, kernel won't do this replacement. User can modify its value according to specific CPU/applications. Thanks for Borislav providing the help message of CONFIG_DEBUG_TLBFLUSH. Signed-off-by: Alex Shi Link: http://lkml.kernel.org/r/1340845344-27557-6-git-send-email-alex.shi@intel.com Signed-off-by: H. Peter Anvin --- arch/x86/Kconfig.debug | 19 +++++++++++++++++++ arch/x86/mm/tlb.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 70 insertions(+) diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index e46c21473..b322f12 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -129,6 +129,25 @@ config DOUBLEFAULT option saves about 4k and might cause you much additional grey hair. +config DEBUG_TLBFLUSH + bool "Set upper limit of TLB entries to flush one-by-one" + depends on DEBUG_KERNEL && (X86_64 || X86_INVLPG) + ---help--- + + X86-only for now. + + This option allows the user to tune the amount of TLB entries the + kernel flushes one-by-one instead of doing a full TLB flush. In + certain situations, the former is cheaper. This is controlled by the + tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it + to -1, the code flushes the whole TLB unconditionally. Otherwise, + for positive values of it, the kernel will use single TLB entry + invalidating instructions according to the following formula: + + flush_entries <= active_tlb_entries / 2^tlb_flushall_shift + + If in doubt, say "N". + config IOMMU_DEBUG bool "Enable IOMMU debugging" depends on GART_IOMMU && DEBUG_KERNEL diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c index 2939f2f..5911f61 100644 --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -12,6 +12,7 @@ #include #include #include +#include DEFINE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate) = { &init_mm, 0, }; @@ -430,3 +431,53 @@ void flush_tlb_all(void) { on_each_cpu(do_flush_tlb_all, NULL, 1); } + +#ifdef CONFIG_DEBUG_TLBFLUSH +static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf, + size_t count, loff_t *ppos) +{ + char buf[32]; + unsigned int len; + + len = sprintf(buf, "%hd\n", tlb_flushall_shift); + return simple_read_from_buffer(user_buf, count, ppos, buf, len); +} + +static ssize_t tlbflush_write_file(struct file *file, + const char __user *user_buf, size_t count, loff_t *ppos) +{ + char buf[32]; + ssize_t len; + s8 shift; + + len = min(count, sizeof(buf) - 1); + if (copy_from_user(buf, user_buf, len)) + return -EFAULT; + + buf[len] = '\0'; + if (kstrtos8(buf, 0, &shift)) + return -EINVAL; + + if (shift > 64) + return -EINVAL; + + tlb_flushall_shift = shift; + return count; +} + +static const struct file_operations fops_tlbflush = { + .read = tlbflush_read_file, + .write = tlbflush_write_file, + .llseek = default_llseek, +}; + +static int __cpuinit create_tlb_flushall_shift(void) +{ + if (cpu_has_invlpg) { + debugfs_create_file("tlb_flushall_shift", S_IRUSR | S_IWUSR, + arch_debugfs_dir, NULL, &fops_tlbflush); + } + return 0; +} +late_initcall(create_tlb_flushall_shift); +#endif -- 2.7.4