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authorLennart Poettering <lennart@poettering.net>2009-11-05 03:23:08 +0100
committerLennart Poettering <lennart@poettering.net>2009-11-11 05:26:36 +0100
commit3b2530255460e5700766fcd7c7443b7065240f61 (patch)
tree0f3ac47809690326be4c42ad9ed4a8760932b156 /src/modules/alsa/alsa-util.c
parent5da02977444805aabb6665d14bd74563941a7b15 (diff)
alsa: disable timer-based scheduling inside a VM
In virtual machines sound card clocks and OS scheduling tend to become unreliable, adding various 'uneven' latencies. The adaptive algorithm that handles drop-outs does not handle it this well: in contrast to drop-outs on real machines that are evenly distributed, small and can easily be encountered via the adpative algorithms, drop-outs in VMs tend to happen abruptly, and massively, which is not easy to counter. This patch simply disables timer based scheduling in VMs reverting to classic IO based scheduling. This should help make PA perform better in VMs. https://bugzilla.redhat.com/show_bug.cgi?id=532775
Diffstat (limited to 'src/modules/alsa/alsa-util.c')
-rw-r--r--src/modules/alsa/alsa-util.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c
index 0e22d17e..b8d13575 100644
--- a/src/modules/alsa/alsa-util.c
+++ b/src/modules/alsa/alsa-util.c
@@ -43,6 +43,7 @@
#include <pulsecore/once.h>
#include <pulsecore/thread.h>
#include <pulsecore/conf-parser.h>
+#include <pulsecore/core-rtclock.h>
#include "alsa-util.h"
#include "alsa-mixer.h"
@@ -1308,3 +1309,26 @@ const char* pa_alsa_strerror(int errnum) {
return translated;
}
+
+pa_bool_t pa_alsa_may_tsched(pa_bool_t want) {
+
+ if (!want)
+ return FALSE;
+
+ if (!pa_rtclock_hrtimer()) {
+ /* We cannot depend on being woken up in time when the timers
+ are inaccurate, so let's fallback to classic IO based playback
+ then. */
+ pa_log_notice("Disabling timer-based scheduling because high-resolution timers are not available from the kernel.");
+ return FALSE; }
+
+ if (pa_running_in_vm()) {
+ /* We cannot depend on being woken up when we ask for in a VM,
+ * so let's fallback to classic IO based playback then. */
+ pa_log_notice("Disabling timer-based scheduling because running inside a VM.");
+ return FALSE;
+ }
+
+
+ return TRUE;
+}