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Message-ID: <tip-126abdc40ba5257c5ba1e6e04b809c3626034ee9@git.kernel.org>
Date: Tue, 26 Jun 2012 08:16:29 -0700
From: tip-bot for Alex Shi <alex.shi@...el.com>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
alex.shi@...el.com, tglx@...utronix.de
Subject: [tip:x86/mm] x86/tlb: add tlb_flushall_shift knob into debugfs
Commit-ID: 126abdc40ba5257c5ba1e6e04b809c3626034ee9
Gitweb: http://git.kernel.org/tip/126abdc40ba5257c5ba1e6e04b809c3626034ee9
Author: Alex Shi <alex.shi@...el.com>
AuthorDate: Mon, 25 Jun 2012 14:08:23 +0800
Committer: H. Peter Anvin <hpa@...or.com>
CommitDate: Mon, 25 Jun 2012 20:53:18 -0700
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 <alex.shi@...el.com>
Link: http://lkml.kernel.org/r/1340604507-11214-6-git-send-email-alex.shi@intel.com
Signed-off-by: H. Peter Anvin <hpa@...or.com>
---
arch/x86/Kconfig.debug | 19 +++++++++++++++++
arch/x86/mm/tlb.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 70 insertions(+), 0 deletions(-)
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index e46c214..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 <asm/cache.h>
#include <asm/apic.h>
#include <asm/uv/uv.h>
+#include <linux/debugfs.h>
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
--
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