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    SubjectRe: [RFC] QoS params patch
    On Wed, Sep 26, 2007 at 04:41:59PM -0700, Randy Dunlap wrote:
    > On Wed, 26 Sep 2007 15:40:26 -0700 Mark Gross wrote:
    >
    > > The following is the qos_param patch that implements a genralization of
    > > latency.c.
    > >
    >
    > Just some general comments (as on irc):
    >
    > - use 'diffstat -p1 -w70' to summarize each patch
    > - use checkpatch.pl to check for coding style and other buglets

    done

    > - has no API docs :(
    not done yet.
    >
    >
    >
    >
    > > +/* assumes qos_lock is held */
    > > +static void update_target(int i)
    >
    > I'd prefer a better arg name than 'i'.

    I do too, but i in this case is an Index.

    > > +{
    >
    > ---
    > ~Randy
    > Phaedrus says that Quality is about caring.

    updated patch:

    Signed-off-by: mark gross <mgross@linux.intel.com>
    Makefile | 2
    linux/qos_params.h | 35 +++++
    qos_params.c | 354 +++++++++++++++++++++++++++++++++++++++++++++++++++++
    3 files changed, 390 insertions(+), 1 deletion(-)



    diff -urN -X linux-2.6.23-rc8/Documentation/dontdiff linux-2.6.23-rc8/include/linux/qos_params.h linux-2.6.23-rc8-qos/include/linux/qos_params.h
    --- linux-2.6.23-rc8/include/linux/qos_params.h 1969-12-31 16:00:00.000000000 -0800
    +++ linux-2.6.23-rc8-qos/include/linux/qos_params.h 2007-09-26 14:05:20.000000000 -0700
    @@ -0,0 +1,35 @@
    +/* interface for the qos_power infrastructure of the linux kernel.
    + *
    + * Mark Gross
    + */
    +#include <linux/list.h>
    +#include <linux/notifier.h>
    +#include <linux/miscdevice.h>
    +
    +struct requirement_list {
    + struct list_head list;
    + union {
    + s32 value;
    + s32 usec;
    + s32 kbps;
    + };
    + char *name;
    +};
    +
    +#define QOS_RESERVED 0
    +#define QOS_CPU_DMA_LATENCY 1
    +#define QOS_NETWORK_LATENCY 2
    +#define QOS_NETWORK_THROUGHPUT 3
    +
    +#define QOS_NUM_CLASSES 4
    +#define QOS_DEFAULT_VALUE -1
    +
    +int qos_add_requirement(int qos, char *name, s32 value);
    +int qos_update_requirement(int qos, char *name, s32 new_value);
    +void qos_remove_requirement(int qos, char *name);
    +
    +int qos_requirement(int qos);
    +
    +int qos_add_notifier(int qos, struct notifier_block *notifier);
    +int qos_remove_notifier(int qos, struct notifier_block *notifier);
    +
    diff -urN -X linux-2.6.23-rc8/Documentation/dontdiff linux-2.6.23-rc8/kernel/Makefile linux-2.6.23-rc8-qos/kernel/Makefile
    --- linux-2.6.23-rc8/kernel/Makefile 2007-09-26 13:54:54.000000000 -0700
    +++ linux-2.6.23-rc8-qos/kernel/Makefile 2007-09-26 14:06:38.000000000 -0700
    @@ -9,7 +9,7 @@
    rcupdate.o extable.o params.o posix-timers.o \
    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
    hrtimer.o rwsem.o latency.o nsproxy.o srcu.o die_notifier.o \
    - utsname.o
    + utsname.o qos_params.o

    obj-$(CONFIG_STACKTRACE) += stacktrace.o
    obj-y += time/
    diff -urN -X linux-2.6.23-rc8/Documentation/dontdiff linux-2.6.23-rc8/kernel/qos_params.c linux-2.6.23-rc8-qos/kernel/qos_params.c
    --- linux-2.6.23-rc8/kernel/qos_params.c 1969-12-31 16:00:00.000000000 -0800
    +++ linux-2.6.23-rc8-qos/kernel/qos_params.c 2007-09-26 17:09:44.000000000 -0700
    @@ -0,0 +1,354 @@
    +/*
    + * This module exposes the interface to kernel space for specifying
    + * QoS dependencies. It provides infrastructure for registration of:
    + *
    + * Dependents on a QoS value : register requirements
    + * Watchers of QoS value : get notified when target QoS value changes
    + *
    + * This QoS design is best effort based. Dependents register their QoS needs.
    + * Watchers register to keep track of the current QoS needs of the system.
    + *
    + * There are 3 basic classes of QoS parameter: latency, timeout, throughput
    + * each have defined units:
    + * latency: usec
    + * timeout: usec <-- currently not used.
    + * throughput: kbs (kilo byte / sec)
    + *
    + * There are lists of qos_objects each one wrapping requirements, notifiers
    + *
    + * User mode requirements on a QOS parameter register themselves to the
    + * subsystem by opening the device node /dev/... and writing there request to
    + * the node. As long as the process holds a file handle open to the node the
    + * client continues to be accounted for. Upon file release the usermode
    + * requirement is removed and a new qos target is computed. This way when the
    + * requirement that the application has is cleaned up when closes the file
    + * pointer or exits the qos_object will get an opportunity to clean up.
    + *
    + * mark gross mgross@linux.intel.com
    + */
    +
    +#include <linux/qos_params.h>
    +#include <linux/sched.h>
    +#include <linux/spinlock.h>
    +#include <linux/slab.h>
    +#include <linux/time.h>
    +#include <linux/fs.h>
    +#include <linux/device.h>
    +#include <linux/miscdevice.h>
    +#include <linux/string.h>
    +#include <linux/platform_device.h>
    +#include <linux/init.h>
    +
    +#include <linux/uaccess.h>
    +
    +/*
    + * locking rule: all changes to target_value or requirements or notifiers lists
    + * or qos_object list and qos_objects need to happen with qos_lock held, taken
    + * with _irqsave. One lock to rule them all
    + */
    +
    +struct qos_object {
    + struct requirement_list requirements;
    + struct srcu_notifier_head notifiers;
    + struct miscdevice qos_power_miscdev;
    + char *name;
    + s32 default_value;
    + s32 target_value;
    + s32 (*comparitor)(s32, s32);
    +};
    +static struct qos_object qos_array[QOS_NUM_CLASSES];
    +static DEFINE_SPINLOCK(qos_lock);
    +
    +static ssize_t qos_power_write(struct file *filp, const char __user *buf,
    + size_t count, loff_t *f_pos);
    +static int qos_power_open(struct inode *inode, struct file *filp);
    +static int qos_power_release(struct inode *inode, struct file *filp);
    +
    +static const struct file_operations qos_power_fops = {
    + .write = qos_power_write,
    + .open = qos_power_open,
    + .release = qos_power_release,
    +};
    +
    +/* static helper functions */
    +static s32 max_compare(s32 v1, s32 v2)
    +{
    + if (v1 < v2)
    + return v2;
    + else
    + return v1;
    +}
    +
    +static s32 min_compare(s32 v1, s32 v2)
    +{
    + if (v1 < v2)
    + return v1;
    + else
    + return v2;
    +}
    +
    +/* assumes qos_lock is held */
    +static void update_target(int i)
    +{
    + s32 extreme_value;
    + struct requirement_list *node;
    +
    + extreme_value = qos_array[i].default_value;
    + list_for_each_entry(node, &qos_array[i].requirements.list, list) {
    + extreme_value = qos_array[i].comparitor(
    + extreme_value, node->value);
    + }
    + if (qos_array[i].target_value != extreme_value) {
    + qos_array[i].target_value = extreme_value;
    + printk(KERN_ERR "new target for qos %d is %d\n", i,
    + qos_array[i].target_value);
    + srcu_notifier_call_chain(&qos_array[i].notifiers,
    + (unsigned long) qos_array[i].target_value, NULL);
    + }
    +}
    +
    +static int register_new_qos_misc(struct qos_object *qos)
    +{
    + int ret;
    +
    + qos->qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
    + qos->qos_power_miscdev.name = qos->name;
    + qos->qos_power_miscdev.fops = &qos_power_fops;
    +
    + ret = misc_register(& qos->qos_power_miscdev);
    + if (ret < 0)
    + printk(KERN_ERR "qos_power: misc_register returns %d.\n", ret);
    +
    + return ret;
    +}
    +
    +
    +/* constructors */
    +static void init_qos_object(int i, const char *name, s32 default_value,
    + s32 (*comparitor)(s32, s32))
    +{
    + struct qos_object *qos = NULL;
    +
    + if (i < QOS_NUM_CLASSES) {
    + qos = &qos_array[i];
    + qos->name = kstrdup(name, GFP_KERNEL);
    + if (!qos->name)
    + goto cleanup;
    +
    + qos->default_value = default_value;
    + qos->target_value = default_value;
    + qos->comparitor = comparitor;
    + srcu_init_notifier_head(&qos->notifiers);
    + INIT_LIST_HEAD(&qos->requirements.list);
    + if (register_new_qos_misc(qos) < 0)
    + goto cleanup;
    + }
    + return;
    +cleanup:
    + kfree(qos->name);
    +}
    +
    +static int find_qos_object_by_minor(int minor)
    +{
    + int i;
    +
    + for (i = 0; i < QOS_NUM_CLASSES; i++) {
    + if (minor == qos_array[i].qos_power_miscdev.minor)
    + return i;
    + }
    + return -1;
    +}
    +
    +static void new_latency_qos(int i, const char *name)
    +{
    + init_qos_object(i, name, 2000 * USEC_PER_SEC, min_compare);
    + /* 2000 sec is about infinite */
    +}
    +
    +static void new_throughput_qos(int i, const char *name)
    +{
    + init_qos_object(i, name, 0, max_compare);
    +}
    +
    +/* accessors: */
    +
    +int qos_requirement(int i)
    +{
    + int ret_val;
    + unsigned long flags;
    + spin_lock_irqsave(&qos_lock, flags);
    +
    + ret_val = qos_array[i].target_value;
    + spin_unlock_irqrestore(&qos_lock, flags);
    +
    + return ret_val;
    +}
    +EXPORT_SYMBOL_GPL(qos_requirement);
    +
    +
    +int qos_add_requirement(int i, char *name, s32 value)
    +{
    + struct requirement_list *dep;
    + unsigned long flags;
    +
    + spin_lock_irqsave(&qos_lock, flags);
    + dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
    + if (dep) {
    + if (value == QOS_DEFAULT_VALUE)
    + dep->value = qos_array[i].default_value;
    + else
    + dep->value = value;
    + dep->name = kstrdup(name, GFP_KERNEL);
    + if (!dep->name)
    + goto cleanup;
    +
    + list_add(&dep->list, &qos_array[i].requirements.list);
    + update_target(i);
    + spin_unlock_irqrestore(&qos_lock, flags);
    +
    + return 0;
    + }
    + spin_unlock_irqrestore(&qos_lock, flags);
    +
    +cleanup:
    + kfree(dep);
    + return -ENOMEM;
    +}
    +EXPORT_SYMBOL_GPL(qos_add_requirement);
    +
    +
    +int qos_update_requirement(int i, char *name, s32 new_value)
    +{
    + unsigned long flags;
    + struct requirement_list *node;
    + int pending_update = 0;
    +
    + spin_lock_irqsave(&qos_lock, flags);
    + list_for_each_entry(node, &qos_array[i].requirements.list, list) {
    + if (strcmp(node->name, name) == 0) {
    + if (new_value == QOS_DEFAULT_VALUE)
    + node->value = qos_array[i].default_value;
    + else
    + node->value = new_value;
    + pending_update = 1;
    + break;
    + }
    + }
    + if (pending_update)
    + update_target(i);
    +
    + spin_unlock_irqrestore(&qos_lock, flags);
    +
    + return 0;
    +}
    +EXPORT_SYMBOL_GPL(qos_update_requirement);
    +
    +void qos_remove_requirement(int i, char *name)
    +{
    + unsigned long flags;
    + struct requirement_list *node;
    + int pending_update = 0;
    +
    + spin_lock_irqsave(&qos_lock, flags);
    + list_for_each_entry(node, &qos_array[i].requirements.list, list) {
    + if (strcmp(node->name, name) == 0) {
    + kfree(node->name);
    + list_del(&node->list);
    + kfree(node);
    + pending_update = 1;
    + break;
    + }
    + }
    + if (pending_update)
    + update_target(i);
    + spin_unlock_irqrestore(&qos_lock, flags);
    +}
    +EXPORT_SYMBOL_GPL(qos_remove_requirement);
    +
    +int qos_add_notifier(int i, struct notifier_block *notifier)
    +{
    + unsigned long flags;
    + int retval;
    +
    + spin_lock_irqsave(&qos_lock, flags);
    + retval = srcu_notifier_chain_register(&qos_array[i].notifiers,
    + notifier);
    + spin_unlock_irqrestore(&qos_lock, flags);
    +
    + return retval;
    +}
    +EXPORT_SYMBOL_GPL(qos_add_notifier);
    +
    +int qos_remove_notifier(int i, struct notifier_block *notifier)
    +{
    + unsigned long flags;
    + int retval;
    +
    + spin_lock_irqsave(&qos_lock, flags);
    + retval = srcu_notifier_chain_unregister(&qos_array[i].notifiers,
    + notifier);
    + spin_unlock_irqrestore(&qos_lock, flags);
    +
    + return retval;
    +}
    +EXPORT_SYMBOL_GPL(qos_remove_notifier);
    +
    +#define PID_NAME_LEN sizeof("process_1234567890")
    +static char name[PID_NAME_LEN];
    +
    +static int qos_power_open(struct inode *inode, struct file *filp)
    +{
    + int ret;
    + int i;
    +
    + i = find_qos_object_by_minor(iminor(inode));
    + if (i >= 0) {
    + filp->private_data = (void *) i;
    + sprintf(name, "process_%d", current->pid);
    + ret = qos_add_requirement(i, name, QOS_DEFAULT_VALUE);
    + if (ret >= 0)
    + return 0;
    + }
    +
    + return -EPERM;
    +}
    +
    +static int qos_power_release(struct inode *inode, struct file *filp)
    +{
    + int qos;
    +
    + qos = (int) filp->private_data;
    + sprintf(name, "process_%d", current->pid);
    + qos_remove_requirement(qos, name);
    +
    + return 0;
    +}
    +
    +static ssize_t qos_power_write(struct file *filp, const char __user *buf,
    + size_t count, loff_t *f_pos)
    +{
    + s32 value;
    + int qos;
    +
    + qos = (int) filp->private_data;
    + if (count != sizeof(s32))
    + return -EINVAL;
    + if (copy_from_user(&value, buf, sizeof(s32)))
    + return -EFAULT;
    + sprintf(name, "process_%d", current->pid);
    + qos_update_requirement(qos, name, value);
    +
    + return sizeof(s32);
    +}
    +
    +
    +static int __init qos_power_init(void)
    +{
    + new_latency_qos(QOS_CPU_DMA_LATENCY, "cpu_dma_latency");
    + new_latency_qos(QOS_NETWORK_LATENCY, "network_latency");
    + new_throughput_qos(QOS_NETWORK_THROUGHPUT, "network_throughput");
    +
    + return 0;
    +}
    +
    +late_initcall(qos_power_init);
    -
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