Here's a respin of my earlier CPU controller to work on top of Paul
Menage's process container patches.
Problem:
Current CPU scheduler is very task centric, which makes it
difficult to manage cpu resource consumption of a group of
(related) tasks.
For ex: with the current O(1) scheduler, it is possible for a user to
monopolize CPU simply by spawning more and more threads, causing DoS
to other users.
Requirements:
A few of them are:
- Provide means to group tasks from user-land and
specify limits of CPU bandwidth consumption of each group.
CPU bandwidth limit is enforced over some suitable time
period. For ex: a 40% limit could mean the task group's usage
is limited to 4 sec every 10 sec or 24 sec every minute.
- Time period over which bandwidth is controlled to each group
to be configurable (?)
- Work conserving - Do not let the CPU be idle if there are
runnable tasks (even if that means running task-groups that
are above their allowed limit)
- SMP behavior - Limit to be enforced on all CPUs put together
- Real-time tasks - Should be left alone as they are today?
i.e real time tasks across groups should be scheduled as if
they are in same group
- Should cater to requirements of variety of workload characteristics,
including bursty ones (?)
Salient points about this patch:
- Each task-group gets its own runqueue on every cpu.
- In addition, there is an active and expired array of
task-groups themselves. Task-groups that have expired their
quota are put into expired array.
- Task-groups have priorities. Priority of a task-group is the
same as the priority of the highest-priority runnable task it
has. This I feel will retain interactiveness of the system
as it is today.
- Scheduling the next task involves picking highest priority task-group
from active array first and then picking highest-priority task
within it. Both steps are O(1).
- Token are assigned to task-groups based on their assigned
quota. Once they run out of tokens, the task-group is put
in an expired array. Array switch happens when active array
is empty.
- SMP load-balancing is accomplished on the lines of smpnice.
Results of the patch
====================
Machine : 2way x86_64 Intel Xeon (3.6 GHz) box
Note: All test were forced to run on only one CPU using cpusets
1. Volanomark [1]
------------------------------------------------------------------------------
Group A [50% limit] Group B [50% limit]
Elapsed time 35.83 sec 36.6002
Avg throughput 11179.3 msg/sec 10944.3 msg/sec
------------------------------------------------------------------------------
------------------------------------------------------------------------------
Group A [80% limit] Group B [20% limit]
Elapsed time 23.4466 sec 36.1857
Avg throughput 17072 msg/sec 11080 msg/sec
------------------------------------------------------------------------------
2. Kernel compilation
------------------------------------------------------------------------------
Group A [50% limit] Group B [50% limit]
time -p make -j4 bzImage time -p make -j8 bzImage
real 771.00 sec 769.08 sec
------------------------------------------------------------------------------
------------------------------------------------------------------------------
Group A [80% limit] Group B [20% limit]
time -p make -j4 bzImage time -p make -j8 bzImage
real 484.12 sec 769.70 sec
------------------------------------------------------------------------------
--
Regards,
vatsa
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