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    Subject[PATCH v4 7/7] x86/tlb: add tlb_flushall_factor into sysfs for user testing/tuning
    Date
    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 applications.

    Signed-off-by: Alex Shi <alex.shi@intel.com>
    ---
    Documentation/ABI/testing/sysfs-devices-system-cpu | 12 ++++++
    arch/x86/Kconfig.debug | 11 ++++++
    arch/x86/kernel/cpu/common.c | 37 ++++++++++++++++++++
    drivers/base/cpu.c | 4 ++
    include/linux/cpu.h | 4 ++
    5 files changed, 68 insertions(+), 0 deletions(-)

    diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
    index e7be75b..05f8eb7 100644
    --- a/Documentation/ABI/testing/sysfs-devices-system-cpu
    +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
    @@ -78,6 +78,18 @@ Description: Dynamic addition and removal of CPU's. This is not hotplug
    the system. Information writtento the file to remove CPU's
    is architecture specific.

    +What: /sys/devices/system/cpu/tlb_flushall_factor
    +Date: May 2012
    +Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
    +Description: tlb_flushall_factor show and setting interface
    + tlb_flushall_factor shows the balance point in replacing cr3
    + writting with multiple 'invlpg'. It will do this replacement
    + when flush_tlb_lines <= active_lines/2^tlb_flushall_factor
    + If tlb_flushall_factor is -1, means the replacement will be
    + disabled.
    +
    + User can set this for the specific CPU or application.
    +
    What: /sys/devices/system/cpu/cpu#/node
    Date: October 2009
    Contact: Linux memory management mailing list <linux-mm@kvack.org>
    diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
    index e46c214..5b87493 100644
    --- a/arch/x86/Kconfig.debug
    +++ b/arch/x86/Kconfig.debug
    @@ -129,6 +129,17 @@ config DOUBLEFAULT
    option saves about 4k and might cause you much additional grey
    hair.

    +config DEBUG_TLBFLUSH
    + bool "Enable user level tlb flush all setting"
    + depends on DEBUG_KERNEL && (X86_64 || X86_INVLPG)
    + ---help---
    + This option allows user tune tlb_flushall_factor knob that under
    + /sys/devices/system/cpu, set to -1 means do tlb flush all for any
    + multiple tlb lines evacuation demand. Otherwise kernel will use
    + multiple 'invlpg' for the demand when
    + flush_lines <= active_tlb_lines / 2^tlb_flushall_factor
    + If in doubt, say "N"
    +
    config IOMMU_DEBUG
    bool "Enable IOMMU debugging"
    depends on GART_IOMMU && DEBUG_KERNEL
    diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
    index 8879d20..d1986c6 100644
    --- a/arch/x86/kernel/cpu/common.c
    +++ b/arch/x86/kernel/cpu/common.c
    @@ -481,6 +481,43 @@ void __cpuinit cpu_detect_tlb(struct cpuinfo_x86 *c)
    tlb_flushall_factor);
    }

    +#ifdef CONFIG_DEBUG_TLBFLUSH
    +static ssize_t __tlb_flushall_factor_store(const char *buf,
    + size_t count, int smt)
    +{
    + short factor = 0;
    +
    + if (sscanf(buf, "%hd", &factor) != 1)
    + return -EINVAL;
    +
    + tlb_flushall_factor = factor;
    +
    + return count;
    +}
    +
    +static ssize_t tlb_flushall_factor_show(struct device *dev,
    + struct device_attribute *attr,
    + char *buf)
    +{
    + return sprintf(buf, "%hd\n", tlb_flushall_factor);
    +}
    +static ssize_t tlb_flushall_factor_store(struct device *dev,
    + struct device_attribute *attr,
    + const char *buf, size_t count)
    +{
    + return __tlb_flushall_factor_store(buf, count, 0);
    +}
    +
    +static DEVICE_ATTR(tlb_flushall_factor, 0644,
    + tlb_flushall_factor_show,
    + tlb_flushall_factor_store);
    +
    +int __init create_sysfs_tlb_flushall_factor(struct device *dev)
    +{
    + return device_create_file(dev, &dev_attr_tlb_flushall_factor);
    +}
    +#endif
    +
    void __cpuinit detect_ht(struct cpuinfo_x86 *c)
    {
    #ifdef CONFIG_X86_HT
    diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
    index adf937b..dc0f77b 100644
    --- a/drivers/base/cpu.c
    +++ b/drivers/base/cpu.c
    @@ -331,6 +331,10 @@ void __init cpu_dev_init(void)

    cpu_dev_register_generic();

    +#ifdef CONFIG_DEBUG_TLBFLUSH
    + create_sysfs_tlb_flushall_factor(cpu_subsys.dev_root);
    +#endif
    +
    #if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
    sched_create_sysfs_power_savings_entries(cpu_subsys.dev_root);
    #endif
    diff --git a/include/linux/cpu.h b/include/linux/cpu.h
    index ee28844..3eb85a5 100644
    --- a/include/linux/cpu.h
    +++ b/include/linux/cpu.h
    @@ -36,6 +36,10 @@ extern void cpu_remove_dev_attr(struct device_attribute *attr);
    extern int cpu_add_dev_attr_group(struct attribute_group *attrs);
    extern void cpu_remove_dev_attr_group(struct attribute_group *attrs);

    +#ifdef CONFIG_DEBUG_TLBFLUSH
    +extern int create_sysfs_tlb_flushall_factor(struct device *dev);
    +#endif
    +
    extern int sched_create_sysfs_power_savings_entries(struct device *dev);

    #ifdef CONFIG_HOTPLUG_CPU
    --
    1.7.5.4


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