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  1. 29 Dec, 2008 9 commits
    • Gregory Haskins's avatar
      sched: add sched_class->needs_post_schedule() member · 967fc046
      Gregory Haskins authored 
      We currently run class->post_schedule() outside of the rq->lock, which
means that we need to test for the need to post_schedule outside of
the lock to avoid a forced reacquistion.  This is currently not a problem
as we only look at rq->rt.overloaded.  However, we want to enhance this
going forward to look at more state to reduce the need to post_schedule to
a bare minimum set.  Therefore, we introduce a new member-func called
needs_post_schedule() which tests for the post_schedule condtion without
actually performing the work.  Therefore it is safe to call this
function before the rq->lock is released, because we are guaranteed not
to drop the lock at an intermediate point (such as what post_schedule()
may do).

We will use this later in the series

[ rostedt: removed paranoid BUG_ON ]
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
      967fc046
    • Gregory Haskins's avatar
      sched: make double-lock-balance fair · 8f45e2b5
      Gregory Haskins authored 
      double_lock balance() currently favors logically lower cpus since they
often do not have to release their own lock to acquire a second lock.
The result is that logically higher cpus can get starved when there is
a lot of pressure on the RQs.  This can result in higher latencies on
higher cpu-ids.

This patch makes the algorithm more fair by forcing all paths to have
to release both locks before acquiring them again.  Since callsites to
double_lock_balance already consider it a potential preemption/reschedule
point, they have the proper logic to recheck for atomicity violations.
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
      8f45e2b5
    • Gregory Haskins's avatar
      sched: pull only one task during NEWIDLE balancing to limit critical section · 7e96fa58
      Gregory Haskins authored 
      git-id c4acb2c0 attempted to limit
newidle critical section length by stopping after at least one task
was moved.  Further investigation has shown that there are other
paths nested further inside the algorithm which still remain that allow
long latencies to occur with newidle balancing.  This patch applies
the same technique inside balance_tasks() to limit the duration of
this optional balancing operation.
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
CC: Nick Piggin <npiggin@suse.de>
      7e96fa58
    • Gregory Haskins's avatar
      sched: only try to push a task on wakeup if it is migratable · 777c2f38
      Gregory Haskins authored 
      There is no sense in wasting time trying to push a task away that
cannot move anywhere else.  We gain no benefit from trying to push
other tasks at this point, so if the task being woken up is non
migratable, just skip the whole operation.  This reduces overhead
in the wakeup path for certain tasks.
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
      777c2f38
    • Gregory Haskins's avatar
      sched: use highest_prio.next to optimize pull operations · 74ab8e4f
      Gregory Haskins authored 
      We currently take the rq->lock for every cpu in an overload state during
pull_rt_tasks().  However, we now have enough information via the
highest_prio.[curr|next] fields to determine if there is any tasks of
interest to warrant the overhead of the rq->lock, before we actually take
it.  So we use this information to reduce lock contention during the
pull for the case where the source-rq doesnt have tasks that preempt
the current task.
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
      74ab8e4f
    • Gregory Haskins's avatar
      sched: use highest_prio.curr for pull threshold · a8728944
      Gregory Haskins authored 
      highest_prio.curr is actually a more accurate way to keep track of
the pull_rt_task() threshold since it is always up to date, even
if the "next" task migrates during double_lock.  Therefore, stop
looking at the "next" task object and simply use the highest_prio.curr.
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
      a8728944
    • Gregory Haskins's avatar
      sched: track the next-highest priority on each runqueue · e864c499
      Gregory Haskins authored 
      We will use this later in the series to reduce the amount of rq-lock
contention during a pull operation
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
      e864c499
    • Gregory Haskins's avatar
      sched: cleanup inc/dec_rt_tasks · 4d984277
      Gregory Haskins authored 
      Move some common definitions up to the function prologe to simplify the
body logic.
Signed-off-by: default avatarGregory Haskins <ghaskins@novell.com>
      4d984277
    • Sergio Luis's avatar
      x86: mark get_cpu_leaves() with __cpuinit annotation · 6092848a
      Sergio Luis authored 
      Impact: fix section mismatch warning

Commit b2bb8554 ("x86: Remove cpumask games
in x86/kernel/cpu/intel_cacheinfo.c") introduced get_cpu_leaves(), which
references __cpuinit cpuid4_cache_lookup().

Mark get_cpu_leaves() with a __cpuinit annotation.
Signed-off-by: default avatarSergio Luis <sergio@larces.uece.br>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      6092848a
  3. 23 Dec, 2008 4 commits
  5. 19 Dec, 2008 10 commits
  7. 18 Dec, 2008 4 commits
    • Mike Travis's avatar
      x86: use possible_cpus=NUM to extend the possible cpus allowed · 3b11ce7f
      Mike Travis authored 
      Impact: add new boot parameter

Use possible_cpus=NUM kernel parameter to extend the number of possible
cpus.

The ability to HOTPLUG ON cpus that are "possible" but not "present" is
dealt with in a later patch.
Signed-off-by: default avatarMike Travis <travis@sgi.com>
      3b11ce7f
    • Mike Travis's avatar
      x86: fix cpu_mask_to_apicid_and to include cpu_online_mask · a775a38b
      Mike Travis authored 
      Impact: fix potential APIC crash

In determining the destination apicid, there are usually three cpumasks
that are considered: the incoming cpumask arg, cfg->domain and the
cpu_online_mask.  Since we are just introducing the cpu_mask_to_apicid_and
function, make sure it includes the cpu_online_mask in it's evaluation.
[Added with this patch.]

There are two io_apic.c functions that did not previously use the
cpu_online_mask:  setup_IO_APIC_irq and msi_compose_msg.  Both of these
simply used cpu_mask_to_apicid(cfg->domain & TARGET_CPUS), and all but
one arch (NUMAQ[*]) returns only online cpus in the TARGET_CPUS mask,
so the behavior is identical for all cases.

[*: NUMAQ bug?]

Note that alloc_cpumask_var is only used for the 32-bit cases where
it's highly likely that the cpumask set size will be small and therefore
CPUMASK_OFFSTACK=n.  But if that's not the case, failing the allocate
will cause the same return value as the default.
Signed-off-by: default avatarMike Travis <travis@sgi.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      a775a38b
    • Ingo Molnar's avatar
      Merge branch 'x86/apic' into cpus4096 · 9a3d8f73
      Ingo Molnar authored 
      This done for conflict prevention: we merge it into the cpus4096 tree
because upcoming cpumask changes will touch apic.c that would collide
with x86/apic otherwise.
      9a3d8f73
    • Ingo Molnar's avatar
      Merge branch 'linus' into cpus4096 · b9974dc6
      Ingo Molnar authored
      b9974dc6
  9. 17 Dec, 2008 13 commits
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