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SubjectRe: [patch 2/4] This patch enhances OProfile to support System zs hardware sampling feature
On 20.12.10 08:05:43, graalfs@linux.vnet.ibm.com wrote:
> From: graalfs@linux.vnet.ibm.com
>
> OProfile is enhanced to export all files for controlling System z's hardware sampling,
> and to invoke hwsampler exported functions to initialize and use System z's hardware sampling.
>
> The patch invokes hwsampler_setup() during oprofile init and exports following
> hwsampler files under oprofilefs if hwsampler's setup succeeded:
>
> A new directory for hardware sampling based files
>
> /dev/oprofile/hwsampling/
>
> The userland daemon must explicitly write to the following files
> to disable (or enable) hardware based sampling
>
> /dev/oprofile/hwsampling/hwsampler
>
> to modify the actual sampling rate
>
> /dev/oprofile/hwsampling/hw_interval
>
> to modify the amount of sampling memory (measured in 4K pages)
>
> /dev/oprofile/hwsampling/hw_sdbt_blocks
>
> The following files are read only and show
> the possible minimum sampling rate
>
> /dev/oprofile/hwsampling/hw_min_interval
>
> the possible maximum sampling rate
>
> /dev/oprofile/hwsampling/hw_max_interval
>
> The patch splits the oprofile_timer_[init/exit] function so that it can be also called
> through user context (oprofilefs) to avoid kernel oops.
>
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> Signed-off-by: Maran Pakkirisamy <maranp@linux.vnet.ibm.com>
> Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
> ---
> arch/s390/oprofile/Makefile | 1
> arch/s390/oprofile/hwsampler_files.c | 120 +++++++++++++++++++++++++++++++++++

I would rather see a file hwsampler.c here that contains all oprofile
hwsampler code in it and also sets up a struct oprofile_operations*
ops.

Doing so, most of global functions and variables below can be made
static.

> arch/s390/oprofile/init.c | 35 ++++++++++

We should find a better solution than changing all those files only
for a single architecture:

> drivers/oprofile/oprof.c | 37 ++++++++++
> drivers/oprofile/oprof.h | 2
> drivers/oprofile/timer_int.c | 16 +++-
> include/linux/oprofile.h | 15 ++++

I want to see most of this in arch/s390.

> 7 files changed, 223 insertions(+), 3 deletions(-)
>
> Index: linux-2.6/arch/s390/oprofile/Makefile
> ===================================================================
> --- linux-2.6.orig/arch/s390/oprofile/Makefile
> +++ linux-2.6/arch/s390/oprofile/Makefile
> @@ -8,6 +8,7 @@ DRIVER_OBJS = $(addprefix ../../../drive
> timer_int.o )
>
> oprofile-y := $(DRIVER_OBJS) init.o backtrace.o
> +oprofile-y += $(if $(CONFIG_HWSAMPLER), hwsampler_files.o,)
>
> HW_SAMPLER_DRIVER_OBJS = $(addprefix ../../../drivers/s390/hwsampler/, \
> hwsampler-main.o smpctl.o )
> Index: linux-2.6/arch/s390/oprofile/hwsampler_files.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6/arch/s390/oprofile/hwsampler_files.c
> @@ -0,0 +1,120 @@
> +/**
> + * arch/s390/oprofile/hwsampler_files.c
> + *
> + * Copyright IBM Corp. 2010
> + * Author: Mahesh Salgaonkar (mahesh@linux.vnet.ibm.com)
> + */
> +#include <linux/oprofile.h>
> +#include <linux/errno.h>
> +#include <linux/fs.h>
> +
> +#include <asm/hwsampler.h>
> +
> +#define DEFAULT_INTERVAL 4096
> +
> +#define DEFAULT_SDBT_BLOCKS 1
> +#define DEFAULT_SDB_BLOCKS 511
> +
> +static unsigned long oprofile_hw_interval = DEFAULT_INTERVAL;
> +unsigned long oprofile_min_interval;
> +unsigned long oprofile_max_interval;

This could be static.

> +
> +static unsigned long oprofile_sdbt_blocks = DEFAULT_SDBT_BLOCKS;
> +static unsigned long oprofile_sdb_blocks = DEFAULT_SDB_BLOCKS;
> +
> +static unsigned long oprofile_hwsampler;
> +
> +static int oprofile_hwsampler_start(void)
> +{
> + int retval;
> +
> + printk(KERN_INFO "oprofile_hwsampler_start\n");

This looks like a debug msg.

> +
> + retval = hwsampler_allocate(oprofile_sdbt_blocks, oprofile_sdb_blocks);
> + if (retval)
> + return retval;
> +
> + retval = hwsampler_start_all(oprofile_hw_interval);
> +
> + return retval;
> +}
> +
> +static void oprofile_hwsampler_stop(void)
> +{
> + printk(KERN_INFO "oprofile_hwsampler_stop\n");

Same here.

> +
> + hwsampler_stop_all();
> + hwsampler_deallocate();
> + return;
> +}
> +
> +int oprofile_arch_set_hwsampler(struct oprofile_operations *ops)
> +{
> + printk(KERN_INFO "oprofile: using hardware sampling\n");
> + ops->start = oprofile_hwsampler_start;
> + ops->stop = oprofile_hwsampler_stop;
> + ops->cpu_type = "timer";

Wouldn't it be better to have a different cpu_type string here, I
don't think the oprofilefs interface is exactly the same as for timer
mode. How the daemon distinguishs between both modes?

> +
> + return 0;
> +}
> +
> +static ssize_t hwsampler_read(struct file *file, char __user *buf,
> + size_t count, loff_t *offset)
> +{
> + return oprofilefs_ulong_to_user(oprofile_hwsampler, buf, count, offset);
> +}
> +
> +static ssize_t hwsampler_write(struct file *file, char const __user *buf,
> + size_t count, loff_t *offset)
> +{
> + unsigned long val;
> + int retval;
> +
> + if (*offset)
> + return -EINVAL;
> +
> + retval = oprofilefs_ulong_from_user(&val, buf, count);
> + if (retval)
> + return retval;
> +
> + if (oprofile_hwsampler == val)
> + return -EINVAL;
> +
> + retval = oprofile_set_hwsampler(val);
> +
> + if (retval)
> + return retval;
> +
> + oprofile_hwsampler = val;
> + return count;
> +}
> +
> +static const struct file_operations hwsampler_fops = {
> + .read = hwsampler_read,
> + .write = hwsampler_write,
> +};
> +
> +int oprofile_create_hwsampling_files(struct super_block *sb,
> + struct dentry *root)

This can be made static too.

> +{
> + struct dentry *hw_dir;
> +
> + /* reinitialize default values */
> + oprofile_hwsampler = 1;
> +
> + hw_dir = oprofilefs_mkdir(sb, root, "hwsampling");
> + if (!hw_dir)
> + return -EINVAL;
> +
> + oprofilefs_create_file(sb, hw_dir, "hwsampler", &hwsampler_fops);
> + oprofilefs_create_ulong(sb, hw_dir, "hw_interval",
> + &oprofile_hw_interval);
> + oprofilefs_create_ro_ulong(sb, hw_dir, "hw_min_interval",
> + &oprofile_min_interval);
> + oprofilefs_create_ro_ulong(sb, hw_dir, "hw_max_interval",
> + &oprofile_max_interval);
> + oprofilefs_create_ulong(sb, hw_dir, "hw_sdbt_blocks",
> + &oprofile_sdbt_blocks);
> +
> + return 0;
> +}
> Index: linux-2.6/drivers/oprofile/oprof.c
> ===================================================================
> --- linux-2.6.orig/drivers/oprofile/oprof.c
> +++ linux-2.6/drivers/oprofile/oprof.c
> @@ -239,10 +239,43 @@ int oprofile_set_ulong(unsigned long *ad
> return err;
> }
>
> +#ifdef CONFIG_OPROFILE_HWSAMPLING_MODE
> +int oprofile_set_hwsampler(unsigned long val)
> +{
> + int err = 0;
> +
> + mutex_lock(&start_mutex);
> +
> + if (oprofile_started) {
> + err = -EBUSY;
> + goto out;
> + }
> +
> + switch (val) {
> + case 1:
> + /* Switch to hardware sampling. */
> + __oprofile_timer_exit();
> + err = oprofile_arch_set_hwsampler(&oprofile_ops);
> + break;
> + case 0:
> + printk(KERN_INFO "oprofile: using timer interrupt.\n");
> + err = __oprofile_timer_init(&oprofile_ops);
> + break;

Is there a use case for switching the mode at runtime? There are
kernel parameters to force timer mode while booting or loading the
module. I don't like exporting all these timer and hwsampler
functions. We could avoid this by making hwsampler architectural code
and leaving the timer code as it is.

> + default:
> + err = -EINVAL;
> + }
> +
> +out:
> + mutex_unlock(&start_mutex);
> + return err;
> +}
> +#endif /* CONFIG_OPROFILE_HWSAMPLING_MODE */
> +
> static int __init oprofile_init(void)
> {
> int err;
>
> + memset(&oprofile_ops, 0, sizeof(oprofile_ops));

The struct is already initialized to 0.

> err = oprofile_arch_init(&oprofile_ops);
> if (err < 0 || timer) {
> printk(KERN_INFO "oprofile: using timer interrupt.\n");
> @@ -250,6 +283,10 @@ static int __init oprofile_init(void)
> if (err)
> return err;
> }
> +#ifdef CONFIG_OPROFILE_HWSAMPLING_MODE
> + else if (err == 0)
> + oprofile_arch_set_hwsampler(&oprofile_ops);

I would like to see this in oprofile_arch_init().

> +#endif
> return oprofilefs_register();
> }
>
> Index: linux-2.6/drivers/oprofile/oprof.h
> ===================================================================
> --- linux-2.6.orig/drivers/oprofile/oprof.h
> +++ linux-2.6/drivers/oprofile/oprof.h
> @@ -35,7 +35,9 @@ struct dentry;
>
> void oprofile_create_files(struct super_block *sb, struct dentry *root);
> int oprofile_timer_init(struct oprofile_operations *ops);
> +int __oprofile_timer_init(struct oprofile_operations *ops);
> void oprofile_timer_exit(void);
> +void __oprofile_timer_exit(void);

See my comments above, I don't want to export this.

>
> int oprofile_set_ulong(unsigned long *addr, unsigned long val);
> int oprofile_set_timeout(unsigned long time);
> Index: linux-2.6/drivers/oprofile/timer_int.c
> ===================================================================
> --- linux-2.6.orig/drivers/oprofile/timer_int.c
> +++ linux-2.6/drivers/oprofile/timer_int.c
> @@ -97,14 +97,13 @@ static struct notifier_block __refdata o
> .notifier_call = oprofile_cpu_notify,
> };
>
> -int __init oprofile_timer_init(struct oprofile_operations *ops)
> +int __oprofile_timer_init(struct oprofile_operations *ops)
> {
> int rc;
>
> rc = register_hotcpu_notifier(&oprofile_cpu_notifier);
> if (rc)
> return rc;
> - ops->create_files = NULL;
> ops->setup = NULL;
> ops->shutdown = NULL;
> ops->start = oprofile_hrtimer_start;
> @@ -113,7 +112,18 @@ int __init oprofile_timer_init(struct op
> return 0;
> }
>
> -void __exit oprofile_timer_exit(void)
> +int __init oprofile_timer_init(struct oprofile_operations *ops)
> +{
> + return __oprofile_timer_init(ops);
> +}
> +
> +void __oprofile_timer_exit(void)
> {
> unregister_hotcpu_notifier(&oprofile_cpu_notifier);
> }
> +
> +void __exit oprofile_timer_exit(void)
> +{
> + __oprofile_timer_exit();
> +}
> +
> Index: linux-2.6/include/linux/oprofile.h
> ===================================================================
> --- linux-2.6.orig/include/linux/oprofile.h
> +++ linux-2.6/include/linux/oprofile.h
> @@ -89,6 +89,21 @@ int oprofile_arch_init(struct oprofile_o
> */
> void oprofile_arch_exit(void);
>
> +#ifdef CONFIG_OPROFILE_HWSAMPLING_MODE
> +/**
> + * setup hardware sampler for oprofiling.
> + */
> +
> +int oprofile_set_hwsampler(unsigned long);
> +
> +/**
> + * hardware sampler module initialization for the s390 arch
> + */
> +
> +int oprofile_arch_set_hwsampler(struct oprofile_operations *ops);

This is not generic code, there is no other architecture that may
reuse this. We should move this to arch/s390.

> +
> +#endif /* CONFIG_OPROFILE_HWSAMPLING_MODE */
> +
> /**
> * Add a sample. This may be called from any context.
> */
> Index: linux-2.6/arch/s390/oprofile/init.c
> ===================================================================
> --- linux-2.6.orig/arch/s390/oprofile/init.c
> +++ linux-2.6/arch/s390/oprofile/init.c
> @@ -11,16 +11,51 @@
> #include <linux/oprofile.h>
> #include <linux/init.h>
> #include <linux/errno.h>
> +#include <linux/fs.h>
>
> +#ifdef CONFIG_OPROFILE_HWSAMPLING_MODE
> +#include <asm/hwsampler.h>
> +
> +extern int oprofile_create_hwsampling_files(struct super_block *sb,
> + struct dentry *root);
> +
> +extern unsigned long oprofile_min_interval;
> +extern unsigned long oprofile_max_interval;

This becomes static if we move it to arch/s390/oprofile/hwsampler.c
(see below).

> +#endif /* CONFIG_OPROFILE_HWSAMPLING_MODE */
>
> extern void s390_backtrace(struct pt_regs * const regs, unsigned int depth);
>
> int __init oprofile_arch_init(struct oprofile_operations* ops)
> {
> ops->backtrace = s390_backtrace;
> +
> +#ifdef CONFIG_OPROFILE_HWSAMPLING_MODE
> + if (hwsampler_setup())
> + return -ENODEV;
> +
> + /*
> + * create hwsampler files only if hwsampler_setup() succeeds.
> + */
> + ops->create_files = oprofile_create_hwsampling_files;
> + oprofile_min_interval = hwsampler_query_min_interval();
> + if (oprofile_min_interval < 0) {
> + oprofile_min_interval = 0;
> + return -ENODEV;
> + }
> + oprofile_max_interval = hwsampler_query_max_interval();
> + if (oprofile_max_interval < 0) {
> + oprofile_max_interval = 0;
> + return -ENODEV;
> + }
> + return 0;
> +#endif /* CONFIG_OPROFILE_HWSAMPLING_MODE */

Move all the code for CONFIG_OPROFILE_HWSAMPLING_MODE in this file to

arch/s390/oprofile/hwsampler.c

and only export an oprofile_hwsampler_init() function. This can be an
empty function stub for the !CONFIG_OPROFILE_HWSAMPLING_MODE case.

> +
> return -ENODEV;
> }
>
> void oprofile_arch_exit(void)
> {
> +#ifdef CONFIG_OPROFILE_HWSAMPLING_MODE
> + hwsampler_shutdown();
> +#endif /* CONFIG_OPROFILE_HWSAMPLING_MODE */

Same here...

-Robert

> }
>
>

--
Advanced Micro Devices, Inc.
Operating System Research Center



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