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Author SHA1 Message Date

Author	SHA1	Message	Date
Markus Armbruster	d1c81c3496	qapi: Use returned bool to check for failure (again) Commit `012d4c96e2` changed the visitor functions taking Error ** to return bool instead of void, and the commits following it used the new return value to simplify error checking. Since then a few more uses in need of the same treatment crept in. Do that. All pretty mechanical except for * balloon_stats_get_all() This is basically the same transformation commit `012d4c96e2` applied to the virtual walk example in include/qapi/visitor.h. * set_max_queue_size() Additionally replace "goto end of function" by return. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20221121085054.683122-10-armbru@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>	3 years ago
David Hildenbrand	10218ae6d0	util: Add write-only "node-affinity" property for ThreadContext Let's make it easier to pin threads created via a ThreadContext to all host CPUs currently belonging to a given set of host NUMA nodes -- which is the common case. "node-affinity" is simply a shortcut for setting "cpu-affinity" manually to the list of host CPUs belonging to the set of host nodes. This property can only be written. A simple QEMU example to set the CPU affinity to host node 1 on a system with two nodes, 24 CPUs each, whereby odd-numbered host CPUs belong to host node 1: qemu-system-x86_64 -S \ -object thread-context,id=tc1,node-affinity=1 And we can query the cpu-affinity via HMP/QMP: (qemu) qom-get tc1 cpu-affinity [ 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47 ] We cannot query the node-affinity: (qemu) qom-get tc1 node-affinity Error: Insufficient permission to perform this operation But note that due to dynamic library loading this example will not work before we actually make use of thread_context_create_thread() in QEMU code, because the type will otherwise not get registered. We'll wire this up next to make it work. Note that if the host CPUs for a host node change due do CPU hot(un)plug CPU onlining/offlining (i.e., lscpu output changes) after the ThreadContext was started, the CPU affinity will not get updated. Reviewed-by: Michal Privoznik <mprivozn@redhat.com> Acked-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20221014134720.168738-5-david@redhat.com> Signed-off-by: David Hildenbrand <david@redhat.com>	4 years ago
David Hildenbrand	e2de2c497e	util: Introduce ThreadContext user-creatable object Setting the CPU affinity of QEMU threads is a bit problematic, because QEMU doesn't always have permissions to set the CPU affinity itself, for example, with seccomp after initialized by QEMU: -sandbox enable=on,resourcecontrol=deny General information about CPU affinities can be found in the man page of taskset: CPU affinity is a scheduler property that "bonds" a process to a given set of CPUs on the system. The Linux scheduler will honor the given CPU affinity and the process will not run on any other CPUs. While upper layers are already aware of how to handle CPU affinities for long-lived threads like iothreads or vcpu threads, especially short-lived threads, as used for memory-backend preallocation, are more involved to handle. These threads are created on demand and upper layers are not even able to identify and configure them. Introduce the concept of a ThreadContext, that is essentially a thread used for creating new threads. All threads created via that context thread inherit the configured CPU affinity. Consequently, it's sufficient to create a ThreadContext and configure it once, and have all threads created via that ThreadContext inherit the same CPU affinity. The CPU affinity of a ThreadContext can be configured two ways: (1) Obtaining the thread id via the "thread-id" property and setting the CPU affinity manually (e.g., via taskset). (2) Setting the "cpu-affinity" property and letting QEMU try set the CPU affinity itself. This will fail if QEMU doesn't have permissions to do so anymore after seccomp was initialized. A simple QEMU example to set the CPU affinity to host CPU 0,1,6,7 would be: qemu-system-x86_64 -S \ -object thread-context,id=tc1,cpu-affinity=0-1,cpu-affinity=6-7 And we can query it via HMP/QMP: (qemu) qom-get tc1 cpu-affinity [ 0, 1, 6, 7 ] But note that due to dynamic library loading this example will not work before we actually make use of thread_context_create_thread() in QEMU code, because the type will otherwise not get registered. We'll wire this up next to make it work. In general, the interface behaves like pthread_setaffinity_np(): host CPU numbers that are currently not available are ignored; only host CPU numbers that are impossible with the current kernel will fail. If the list of host CPU numbers does not include a single CPU that is available, setting the CPU affinity will fail. A ThreadContext can be reused, simply by reconfiguring the CPU affinity. Note that the CPU affinity of previously created threads will not get adjusted. Reviewed-by: Michal Privoznik <mprivozn@redhat.com> Acked-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20221014134720.168738-4-david@redhat.com> Signed-off-by: David Hildenbrand <david@redhat.com>	4 years ago

Markus Armbruster

d1c81c3496

qapi: Use returned bool to check for failure (again)

Commit 012d4c96e2 changed the visitor functions taking Error ** to
return bool instead of void, and the commits following it used the new
return value to simplify error checking.  Since then a few more uses
in need of the same treatment crept in.  Do that.  All pretty
mechanical except for

* balloon_stats_get_all()

  This is basically the same transformation commit 012d4c96e2 applied
  to the virtual walk example in include/qapi/visitor.h.

* set_max_queue_size()

  Additionally replace "goto end of function" by return.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20221121085054.683122-10-armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

3 years ago

David Hildenbrand

10218ae6d0

util: Add write-only "node-affinity" property for ThreadContext

Let's make it easier to pin threads created via a ThreadContext to
all host CPUs currently belonging to a given set of host NUMA nodes --
which is the common case.

"node-affinity" is simply a shortcut for setting "cpu-affinity" manually
to the list of host CPUs belonging to the set of host nodes. This property
can only be written.

A simple QEMU example to set the CPU affinity to host node 1 on a system
with two nodes, 24 CPUs each, whereby odd-numbered host CPUs belong to
host node 1:
    qemu-system-x86_64 -S \
      -object thread-context,id=tc1,node-affinity=1

And we can query the cpu-affinity via HMP/QMP:
    (qemu) qom-get tc1 cpu-affinity
    [
        1,
        3,
        5,
        7,
        9,
        11,
        13,
        15,
        17,
        19,
        21,
        23,
        25,
        27,
        29,
        31,
        33,
        35,
        37,
        39,
        41,
        43,
        45,
        47
    ]

We cannot query the node-affinity:
    (qemu) qom-get tc1 node-affinity
    Error: Insufficient permission to perform this operation

But note that due to dynamic library loading this example will not work
before we actually make use of thread_context_create_thread() in QEMU
code, because the type will otherwise not get registered. We'll wire
this up next to make it work.

Note that if the host CPUs for a host node change due do CPU hot(un)plug
CPU onlining/offlining (i.e., lscpu output changes) after the ThreadContext
was started, the CPU affinity will not get updated.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20221014134720.168738-5-david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

4 years ago

David Hildenbrand

e2de2c497e

util: Introduce ThreadContext user-creatable object

Setting the CPU affinity of QEMU threads is a bit problematic, because
QEMU doesn't always have permissions to set the CPU affinity itself,
for example, with seccomp after initialized by QEMU:
    -sandbox enable=on,resourcecontrol=deny

General information about CPU affinities can be found in the man page of
taskset:
    CPU affinity is a scheduler property that "bonds" a process to a given
    set of CPUs on the system. The Linux scheduler will honor the given CPU
    affinity and the process will not run on any other CPUs.

While upper layers are already aware of how to handle CPU affinities for
long-lived threads like iothreads or vcpu threads, especially short-lived
threads, as used for memory-backend preallocation, are more involved to
handle. These threads are created on demand and upper layers are not even
able to identify and configure them.

Introduce the concept of a ThreadContext, that is essentially a thread
used for creating new threads. All threads created via that context
thread inherit the configured CPU affinity. Consequently, it's
sufficient to create a ThreadContext and configure it once, and have all
threads created via that ThreadContext inherit the same CPU affinity.

The CPU affinity of a ThreadContext can be configured two ways:

(1) Obtaining the thread id via the "thread-id" property and setting the
    CPU affinity manually (e.g., via taskset).

(2) Setting the "cpu-affinity" property and letting QEMU try set the
    CPU affinity itself. This will fail if QEMU doesn't have permissions
    to do so anymore after seccomp was initialized.

A simple QEMU example to set the CPU affinity to host CPU 0,1,6,7 would be:
    qemu-system-x86_64 -S \
      -object thread-context,id=tc1,cpu-affinity=0-1,cpu-affinity=6-7

And we can query it via HMP/QMP:
    (qemu) qom-get tc1 cpu-affinity
    [
        0,
        1,
        6,
        7
    ]

But note that due to dynamic library loading this example will not work
before we actually make use of thread_context_create_thread() in QEMU
code, because the type will otherwise not get registered. We'll wire
this up next to make it work.

In general, the interface behaves like pthread_setaffinity_np(): host
CPU numbers that are currently not available are ignored; only host CPU
numbers that are impossible with the current kernel will fail. If the
list of host CPU numbers does not include a single CPU that is
available, setting the CPU affinity will fail.

A ThreadContext can be reused, simply by reconfiguring the CPU affinity.
Note that the CPU affinity of previously created threads will not get
adjusted.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20221014134720.168738-4-david@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>

4 years ago

3 Commits (6ccca4b6bb9f994cc04e71004e1767a3476d2b23)