[libvirt] [PATCH v2 2/5] util: allow virProcessSetScheduler to set SCHED_DEADLINE

[Martin Kletzander]

On Mon, Nov 21, 2016 at 01:56:05PM +0100, Martin Polednik wrote:
>As sched_deadline is linux specific, it is not set through
>sched_setscheduler but rather the sched_setattr syscall. Additionally,
>the scheduler has new set of parameters: runtime, deadline and period.
>
>In this part of the series, we extend virProcessSetScheduler to
>accommodate the additional parameters and use sched_setattr syscall to
>set SCHED_DEADLINE. Another small addition is sched_attr struct, which
>is required for sched_setattr and not exposed from the kernel or
>libraries.
>---
> src/qemu/qemu_process.c |  3 ++-
> src/util/virprocess.c   | 37 +++++++++++++++++++++++++++++++++----
> src/util/virprocess.h   | 25 ++++++++++++++++++++++++-
> 3 files changed, 59 insertions(+), 6 deletions(-)
>
>diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
>index 3552a31..e984ccd 100644
>--- a/src/qemu/qemu_process.c
>+++ b/src/qemu/qemu_process.c
>@@ -2395,7 +2395,8 @@ qemuProcessSetupPid(virDomainObjPtr vm,
>
>     /* Set scheduler type and priority. */
>     if (sched &&
>-        virProcessSetScheduler(pid, sched->policy, sched->priority) < 0)
>+        virProcessSetScheduler(pid, sched->policy, sched->priority,
>+                               sched->runtime, sched->deadline, sched->period) < 0)
>         goto cleanup;
>
>     ret = 0;
>diff --git a/src/util/virprocess.c b/src/util/virprocess.c
>index 9b4a555..acf4d6b 100644
>--- a/src/util/virprocess.c
>+++ b/src/util/virprocess.c
>@@ -67,6 +67,7 @@
> VIR_LOG_INIT("util.process");
>
> #ifdef __linux__
>+# include <sys/syscall.h>
> /*
>  * Workaround older glibc. While kernel may support the setns
>  * syscall, the glibc wrapper might not exist. If that's the
>@@ -87,10 +88,8 @@ VIR_LOG_INIT("util.process");
> #   define __NR_setns 339
> #  endif
> # endif
>-
> # ifndef HAVE_SETNS
> #  if defined(__NR_setns)
>-#   include <sys/syscall.h>
>
> static inline int setns(int fd, int nstype)
> {
>@@ -100,6 +99,24 @@ static inline int setns(int fd, int nstype)
> #   error Please determine the syscall number for setns on your architecture
> #  endif
> # endif
>+
>+# if defined(SCHED_DEADLINE) && defined(__NR_sched_setattr)
>+static inline int sched_setattr(pid_t pid,
>+                                const struct sched_attr *attr,
>+                                unsigned int flags)
>+{
>+    return syscall(__NR_sched_setattr, pid, attr, flags);
>+}
>+# else
>+static inline int sched_setattr(pid_t pid,
>+                                const struct sched_attr *attr,
>+                                unsigned int flags)
>+{
>+    virReportSystemError(ENOSYS, "%s",
>+                         _("Deadline scheduler is not supported on this platform."));
>+    return -1;
>+}
>+# endif

As I said, no need to do that, just use AC_CHECK_FUNCS_ONCE we already
have in configure.ac.  Don't redefine it, just error out if it's not
available.

> #else /* !__linux__ */
> static inline int setns(int fd ATTRIBUTE_UNUSED, int nstype ATTRIBUTE_UNUSED)
> {
>@@ -1234,10 +1251,16 @@ virProcessSchedTranslatePolicy(virProcessSchedPolicy policy)
> int
> virProcessSetScheduler(pid_t pid,
>                        virProcessSchedPolicy policy,
>-                       int priority)
>+                       int priority,
>+                       unsigned long long runtime,
>+                       unsigned long long deadline,
>+                       unsigned long long period)
> {
>     struct sched_param param = {0};
>+    struct sched_attr attrs = { sizeof(attrs), SCHED_DEADLINE, 0, 0, 0,
>+                                runtime, deadline, period };
>     int pol = virProcessSchedTranslatePolicy(policy);
>+    int ret = 0;
>
>     VIR_DEBUG("pid=%lld, policy=%d, priority=%u",
>               (long long) pid, policy, priority);
>@@ -1280,7 +1303,13 @@ virProcessSetScheduler(pid_t pid,
>         param.sched_priority = priority;
>     }
>
>-    if (sched_setscheduler(pid, pol, &param) < 0) {
>+    if (pol == SCHED_DEADLINE) {
>+        ret = sched_setattr(pid, &attrs, 0);
>+    } else {
>+        ret = sched_setscheduler(pid, pol, &param);
>+    }
>+
>+    if (ret < 0) {
>         virReportSystemError(errno,
>                              _("Cannot set scheduler parameters for pid %lld"),
>                              (long long) pid);
>diff --git a/src/util/virprocess.h b/src/util/virprocess.h
>index 1eac3e6..02522b4 100644
>--- a/src/util/virprocess.h
>+++ b/src/util/virprocess.h
>@@ -41,6 +41,26 @@ typedef enum {
>
> VIR_ENUM_DECL(virProcessSchedPolicy);
>
>+# ifdef SCHED_DEADLINE
>+struct sched_attr {
>+    uint32_t size;
>+
>+    uint32_t sched_policy;
>+    uint64_t sched_flags;
>+
>+    /* SCHED_NORMAL, SCHED_BATCH */
>+    uint32_t sched_nice;
>+
>+    /* SCHED_FIFO, SCHED_RR */
>+    uint32_t sched_priority;
>+
>+    /* SCHED_DEADLINE (nsec) */
>+    uint64_t sched_runtime;
>+    uint64_t sched_deadline;
>+    uint64_t sched_period;
>+};
>+# endif
>+

There's no need to expose this in a header file, move it to virprocess.c.

> char *
> virProcessTranslateStatus(int status);
>
>@@ -93,6 +113,9 @@ int virProcessRunInMountNamespace(pid_t pid,
>
> int virProcessSetScheduler(pid_t pid,
>                            virProcessSchedPolicy policy,
>-                           int priority);
>+                           int priority,
>+                           unsigned long long runtime,
>+                           unsigned long long deadline,
>+                           unsigned long long period);
>
> #endif /* __VIR_PROCESS_H__ */
>--
>2.8.1
>
>--
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>libvir-list at redhat.com
>https://www.redhat.com/mailman/listinfo/libvir-list
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