200 line linux kernel patch backport to 2.6.34.7

Today morning I read about 200 line linux kernel patch that does wonders here. I found that the patch is for 2.6.37 and increases responsiveness of desktop by 10 times max to 60 times average

It got my curiosity aroused and I wanted to see it in action.

I downloaded the patch from here and tried to  backport it to 2.6.34.7 (downloaded from here)

My maiden attempt to backport the patch succeeded and I compiled and installed the deb file

Here is the backport patch content



diff -urN linux-2.6.34.7/Documentation/kernel-parameters.txt linux/Documentation/kernel-parameters.txt
--- linux-2.6.34.7/Documentation/kernel-parameters.txt    2010-09-13 22:24:58.000000000 +0530
+++ linux/Documentation/kernel-parameters.txt    2010-11-17 22:49:10.082513013 +0530
@@ -1643,6 +1643,9 @@
     noapic        [SMP,APIC] Tells the kernel to not make use of any
             IOAPICs that may be present in the system.

+    noautogroup    Disable scheduler automatic task group creation.
+
+
     nobats        [PPC] Do not use BATs for mapping kernel lowmem
             on "Classic" PPC cores.

diff -urN linux-2.6.34.7/drivers/char/tty_io.c linux/drivers/char/tty_io.c
--- linux-2.6.34.7/drivers/char/tty_io.c    2010-09-13 22:24:58.000000000 +0530
+++ linux/drivers/char/tty_io.c    2010-11-17 22:38:38.750591065 +0530
@@ -3049,6 +3049,7 @@
     put_pid(tsk->signal->tty_old_pgrp);
     tsk->signal->tty = tty_kref_get(tty);
     tsk->signal->tty_old_pgrp = NULL;
+    sched_autogroup_create_attach(tsk);
 }

 static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
diff -urN linux-2.6.34.7/include/linux/sched.h linux/include/linux/sched.h
--- linux-2.6.34.7/include/linux/sched.h    2010-09-13 22:24:58.000000000 +0530
+++ linux/include/linux/sched.h    2010-11-17 21:40:45.286509459 +0530
@@ -514,6 +514,8 @@
     spinlock_t lock;
 };

+struct autogroup;
+
 /*
  * NOTE! "signal_struct" does not have it's own
  * locking, because a shared signal_struct always
@@ -580,6 +582,9 @@

     struct tty_struct *tty; /* NULL if no tty */

+#ifdef CONFIG_SCHED_AUTOGROUP
+    struct autogroup *autogroup;
+#endif
     /*
      * Cumulative resource counters for dead threads in the group,
      * and for reaped dead child processes forked by this group.
@@ -1904,6 +1909,21 @@

 extern unsigned int sysctl_sched_compat_yield;

+#ifdef CONFIG_SCHED_AUTOGROUP
+extern unsigned int sysctl_sched_autogroup_enabled;
+
+extern void sched_autogroup_create_attach(struct task_struct *p);
+extern void sched_autogroup_detach(struct task_struct *p);
+extern void sched_autogroup_fork(struct signal_struct *sig);
+extern void sched_autogroup_exit(struct signal_struct *sig);
+#else
+static inline void sched_autogroup_create_attach(struct task_struct *p) { }
+static inline void sched_autogroup_detach(struct task_struct *p) { }
+static inline void sched_autogroup_fork(struct signal_struct *sig) { }
+static inline void sched_autogroup_exit(struct signal_struct *sig) { }
+#endif
+
+
 #ifdef CONFIG_RT_MUTEXES
 extern int rt_mutex_getprio(struct task_struct *p);
 extern void rt_mutex_setprio(struct task_struct *p, int prio);
diff -urN linux-2.6.34.7/init/Kconfig linux/init/Kconfig
--- linux-2.6.34.7/init/Kconfig    2010-09-13 22:24:58.000000000 +0530
+++ linux/init/Kconfig    2010-11-17 22:48:16.986827765 +0530
@@ -614,6 +614,18 @@

 endif # CGROUPS

+config SCHED_AUTOGROUP
+    bool "Automatic process group scheduling"
+    select CGROUPS
+    select CGROUP_SCHED
+    select FAIR_GROUP_SCHED
+    help
+      This option optimizes the scheduler for common desktop workloads by
+      automatically creating and populating task groups.  This separation
+      of workloads isolates aggressive CPU burners (like build jobs) from
+      desktop applications.  Task group autogeneration is currently based
+      upon task tty association.
+
 config MM_OWNER
     bool

diff -urN linux-2.6.34.7/kernel/fork.c linux/kernel/fork.c
--- linux-2.6.34.7/kernel/fork.c    2010-09-13 22:24:58.000000000 +0530
+++ linux/kernel/fork.c    2010-11-17 22:35:27.942763006 +0530
@@ -886,6 +886,8 @@
     posix_cpu_timers_init_group(sig);

     tty_audit_fork(sig);
+    sched_autogroup_fork(sig);
+

     sig->oom_adj = current->signal->oom_adj;

diff -urN linux-2.6.34.7/kernel/sched_autogroup.c linux/kernel/sched_autogroup.c
--- linux-2.6.34.7/kernel/sched_autogroup.c    1970-01-01 05:30:00.000000000 +0530
+++ linux/kernel/sched_autogroup.c    2010-11-17 22:43:28.726509874 +0530
@@ -0,0 +1,140 @@
+#ifdef CONFIG_SCHED_AUTOGROUP
+
+unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
+
+struct autogroup {
+    struct kref        kref;
+    struct task_group    *tg;
+};
+
+static struct autogroup autogroup_default;
+
+static void autogroup_init(struct task_struct *init_task)
+{
+    autogroup_default.tg = &init_task_group;
+    kref_init(&autogroup_default.kref);
+    init_task->signal->autogroup = &autogroup_default;
+}
+
+static inline void autogroup_destroy(struct kref *kref)
+{
+    struct autogroup *ag = container_of(kref, struct autogroup, kref);
+    struct task_group *tg = ag->tg;
+
+    kfree(ag);
+    sched_destroy_group(tg);
+}
+
+static inline void autogroup_kref_put(struct autogroup *ag)
+{
+    kref_put(&ag->kref, autogroup_destroy);
+}
+
+static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
+{
+    kref_get(&ag->kref);
+    return ag;
+}
+
+static inline struct autogroup *autogroup_create(void)
+{
+    struct autogroup *ag = kmalloc(sizeof(*ag), GFP_KERNEL);
+
+    if (!ag)
+        goto out_fail;
+
+    ag->tg = sched_create_group(&init_task_group);
+    kref_init(&ag->kref);
+
+    if (!(IS_ERR(ag->tg)))
+        return ag;
+
+out_fail:
+    if (ag) {
+        kfree(ag);
+        WARN_ON(1);
+    } else
+        WARN_ON(1);
+
+    return autogroup_kref_get(&autogroup_default);
+}
+
+static inline struct task_group *
+autogroup_task_group(struct task_struct *p, struct task_group *tg)
+{
+    int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
+
+    enabled &= (tg == &root_task_group);
+    enabled &= (p->sched_class == &fair_sched_class);
+    enabled &= (!(p->flags & PF_EXITING));
+
+    if (enabled)
+        return p->signal->autogroup->tg;
+
+    return tg;
+}
+
+static void
+autogroup_move_group(struct task_struct *p, struct autogroup *ag)
+{
+    struct autogroup *prev;
+    struct task_struct *t;
+    struct rq *rq;
+    unsigned long flags;
+
+    rq = task_rq_lock(p, &flags);
+    prev = p->signal->autogroup;
+    if (prev == ag) {
+        task_rq_unlock(rq, &flags);
+        return;
+    }
+
+    p->signal->autogroup = autogroup_kref_get(ag);
+    __sched_move_task(p, rq);
+    task_rq_unlock(rq, &flags);
+
+    rcu_read_lock();
+    list_for_each_entry_rcu(t, &p->thread_group, thread_group) {
+        sched_move_task(t);
+    }
+    rcu_read_unlock();
+
+    autogroup_kref_put(prev);
+}
+
+void sched_autogroup_create_attach(struct task_struct *p)
+{
+    struct autogroup *ag = autogroup_create();
+
+    autogroup_move_group(p, ag);
+    /* drop extra refrence added by autogroup_create() */
+    autogroup_kref_put(ag);
+}
+EXPORT_SYMBOL(sched_autogroup_create_attach);
+
+/* currently has no users */
+void sched_autogroup_detach(struct task_struct *p)
+{
+    autogroup_move_group(p, &autogroup_default);
+}
+EXPORT_SYMBOL(sched_autogroup_detach);
+
+void sched_autogroup_fork(struct signal_struct *sig)
+{
+    sig->autogroup = autogroup_kref_get(current->signal->autogroup);
+}
+
+void sched_autogroup_exit(struct signal_struct *sig)
+{
+    autogroup_kref_put(sig->autogroup);
+}
+
+static int __init setup_autogroup(char *str)
+{
+    sysctl_sched_autogroup_enabled = 0;
+
+    return 1;
+}
+
+__setup("noautogroup", setup_autogroup);
+#endif
diff -urN linux-2.6.34.7/kernel/sched_autogroup.h linux/kernel/sched_autogroup.h
--- linux-2.6.34.7/kernel/sched_autogroup.h    1970-01-01 05:30:00.000000000 +0530
+++ linux/kernel/sched_autogroup.h    2010-11-17 22:39:46.575555847 +0530
@@ -0,0 +1,18 @@
+#ifdef CONFIG_SCHED_AUTOGROUP
+
+static void __sched_move_task(struct task_struct *tsk, struct rq *rq);
+
+static inline struct task_group *
+autogroup_task_group(struct task_struct *p, struct task_group *tg);
+
+#else /* !CONFIG_SCHED_AUTOGROUP */
+
+static inline void autogroup_init(struct task_struct *init_task) {  }
+
+static inline struct task_group *
+autogroup_task_group(struct task_struct *p, struct task_group *tg)
+{
+    return tg;
+}
+
+#endif /* CONFIG_SCHED_AUTOGROUP */
diff -urN linux-2.6.34.7/kernel/sched.c linux/kernel/sched.c
--- linux-2.6.34.7/kernel/sched.c    2010-09-13 22:24:58.000000000 +0530
+++ linux/kernel/sched.c    2010-11-17 22:04:34.054508727 +0530
@@ -77,6 +77,7 @@
 #include

 #include "sched_cpupri.h"
+#include "sched_autogroup.h"

 #define CREATE_TRACE_POINTS
 #include
@@ -311,13 +312,20 @@
 {
     struct task_group *tg;

+
 #ifdef CONFIG_CGROUP_SCHED
-    tg = container_of(task_subsys_state(p, cpu_cgroup_subsys_id),
-                struct task_group, css);
+     struct cgroup_subsys_state *css;
+
+    css = task_subsys_state(p, cpu_cgroup_subsys_id);
+
+    tg = container_of(css, struct task_group, css);
+
+    return autogroup_task_group(p, tg);
 #else
     tg = &init_task_group;
-#endif
+
     return tg;
+#endif
 }

 /* Change a task's cfs_rq and parent entity if it moves across CPUs/groups */
@@ -1935,6 +1943,7 @@
 #include "sched_idletask.c"
 #include "sched_fair.c"
 #include "sched_rt.c"
+#include "sched_autogroup.c"
 #ifdef CONFIG_SCHED_DEBUG
 # include "sched_debug.c"
 #endif
@@ -7738,7 +7747,7 @@
 #ifdef CONFIG_CGROUP_SCHED
     list_add(&init_task_group.list, &task_groups);
     INIT_LIST_HEAD(&init_task_group.children);
-
+    autogroup_init(&init_task);
 #endif /* CONFIG_CGROUP_SCHED */

 #if defined CONFIG_FAIR_GROUP_SCHED && defined CONFIG_SMP
@@ -8257,15 +8266,11 @@
 /* change task's runqueue when it moves between groups.
  *    The caller of this function should have put the task in its new group
  *    by now. This function just updates tsk->se.cfs_rq and tsk->se.parent to
- *    reflect its new group.
+ *    reflect its new group.  Called with the runqueue lock held.
  */
-void sched_move_task(struct task_struct *tsk)
+void __sched_move_task(struct task_struct *tsk, struct rq *rq)
 {
     int on_rq, running;
-    unsigned long flags;
-    struct rq *rq;
-
-    rq = task_rq_lock(tsk, &flags);

     update_rq_clock(rq);

@@ -8288,6 +8293,15 @@
         tsk->sched_class->set_curr_task(rq);
     if (on_rq)
         enqueue_task(rq, tsk, 0, false);
+}
+
+void sched_move_task(struct task_struct *tsk)
+{
+    struct rq *rq;
+    unsigned long flags;
+
+    rq = task_rq_lock(tsk, &flags);
+    __sched_move_task(tsk, rq);

     task_rq_unlock(rq, &flags);
 }
diff -urN linux-2.6.34.7/kernel/sysctl.c linux/kernel/sysctl.c
--- linux-2.6.34.7/kernel/sysctl.c    2010-09-13 22:24:58.000000000 +0530
+++ linux/kernel/sysctl.c    2010-11-17 22:45:38.558806407 +0530
@@ -354,6 +354,17 @@
         .mode        = 0644,
         .proc_handler    = proc_dointvec,
     },
+#ifdef CONFIG_SCHED_AUTOGROUP
+    {
+        .procname    = "sched_autogroup_enabled",
+        .data        = &sysctl_sched_autogroup_enabled,
+        .maxlen        = sizeof(unsigned int),
+        .mode        = 0644,
+        .proc_handler    = proc_dointvec,
+        .extra1        = &zero,
+        .extra2        = &one,
+    },
+#endif
 #ifdef CONFIG_PROVE_LOCKING
     {
         .procname    = "prove_locking",