On Tue, 28 Jul 2020 18:46:00 +0200, Pavel Hofman wrote:
Dne 26. 07. 20 v 20:20 Pavel Hofman napsal(a):
Hi,
I am debugging the following problem with the PCM METER API:
An application with meter/scope configured in .asoundrc hits a high CPU load sometimes when a new playback stream is opened. E.g. in MPD when opening a new radio stream. The 100% CPU core load takes tens of seconds. ...........
TL;DR: at decrease of [status.appl_ptr - status.delay] between consequent runs the size of buffer to convert by the built-in s16 scope is set from usual 100s to huge value of pcm->boundary (1.5G), causing a very long processing at 100% core load.
The debug around the event looks like this, suddenly meter->now drops down:
s16_update 1: meter->now 2567498, s16->old 2566593, size 905 s16_update 1: meter->now 2568401, s16->old 2567498, size 903 s16_update 1: meter->now 20786, s16->old 20786, size 0 s16_update 1: meter->now 1065, s16->old 20786, size -19721 s16_update 1: meter->now 24839, s16->old 24838, size 1 s16_update 1: meter->now 701, s16->old 24839, size -24138 s16_update 1: meter->now 1253162, s16->old 701, size 1252461 s16_update 1: meter->now 1255148, s16->old 1253162, size 1986
..........
s16_update 1: meter->now 11136, s16->old 10261, size 875 s16_update 1: meter->now 22525, s16->old 22524, size 1 s16_update 1: meter->now 963, s16->old 22525, size -21562 s16_update 1: meter->now 1270914, s16->old 963, size 1269951 s16_update 1: meter->now 1272917, s16->old 1270914, size 2003
I think the problem is that s16->old is not reset when status.appl_ptr is zeroed and starts running again. There is a call
static void s16_reset(snd_pcm_scope_t *scope) { snd_pcm_scope_s16_t *s16 = scope->private_data; snd_pcm_meter_t *meter = s16->pcm->private_data; s16->old = meter->now; }
but I do not know when this method is called and whether the meter->now is already assigned to the newly zeroed status.appl_ptr.
Would adding atomic_add(&meter->reset, 1) in snd_pcm_meter_reset() help?
Takashi
Please at which method should I reset s16->old = 0?
- s16_reset
- s16_enable
- s16_start
- snd_pcm_scope_s16_open
Thanks a lot for any help,
Pavel.