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. >