[alsa-devel] [PATCH alsa-lib v2 0/6] pcm: hw: optimization for v2.0.14 of PCM protocol/interface

[Takashi Iwai]

On Fri, 30 Jun 2017 13:37:23 +0200,
Takashi Sakamoto wrote:
> 
> Hi,
> 
> This patchset is a revised version of my previous one:
> 
> [PATCH alsa-lib 00/12] pcm: hw: optimization for v2.0.14 of PCM protocol/interface  
> http://mailman.alsa-project.org/pipermail/alsa-devel/2017-June/122392.html 
> 
> Changes:
>  - add a helper function, 'query_status_and_control_data()' to update appl_ptr
>    in user space.
>  - rename 'query_state()' to 'query_status_data()'
>  - reduce two patches.
>  - aggregate some patches for querying control data.
> 
> I did quick mesurement by execute aplay on x86 machine with.
> 
> 1. With Intel HDA driver with usual configuration.
> ```
> poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
> ioctl(4, SNDRV_PCM_IOCTL_HWSYNC, 0)     = 0
> read(3, "a\23IH\205\177z\257\276]\346\237\313\220L\5\337V\363\351\216\17\346s\22\245-yb\312\37D"..., 16384) = 16384
> ioctl(4, SNDRV_PCM_IOCTL_HWSYNC, 0)     = 0
> poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
> ```
> 
> 2. With Intel HDA driver with 'sync_ptr_ioctl' option to hw PCM plugin.
> ```
> poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55fe03539f80) = 0
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55fe03539f80) = 0
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55fe03539f80) = 0
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55fe03539f80) = 0
> read(3, "Rz\vB\v|A\275\356`\201)\335i3\r}\21Q^\30\324'\r'\375l\235&\3330\2"..., 16384) = 16384
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55fe03539f80) = 0
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55fe03539f80) = 0
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55fe03539f80) = 0
> poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
> ```
> 
> 3. With Fireworks driver with a patch for snd-firewire-lib to add
>    SNDRV_PCM_INFO_SYNC_APPLPTR  support[1].
> ```
> poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
> ioctl(4, SNDRV_PCM_IOCTL_HWSYNC, 0)     = 0
> ioctl(4, SNDRV_PCM_IOCTL_SYNC_PTR, 0x55b647ec9c00) = 0
> read(3, "|\n*\336\322\252*&\377\312\372&\276\333.\207\21\343\362\3\5\363\201\266\3421lZ;\\\22*"..., 24576) = 24576
> ioctl(4, SNDRV_PCM_IOCTL_HWSYNC, 0)     = 0
> poll([{fd=4, events=POLLOUT|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
> ```
> 
> We can see this optimization reduces some ioctl calls in case 3. This is
> due to status data mapping.
> 
> [1] Below.
> diff --git a/sound/firewire/amdtp-stream.c b/sound/firewire/amdtp-stream.c
> index f8c2765..04fb3df 100644
> --- a/sound/firewire/amdtp-stream.c
> +++ b/sound/firewire/amdtp-stream.c
> @@ -160,7 +160,8 @@ int amdtp_stream_add_pcm_hw_constraints(struct amdtp_stream *s,
>                    SNDRV_PCM_INFO_INTERLEAVED |
>                    SNDRV_PCM_INFO_JOINT_DUPLEX |
>                    SNDRV_PCM_INFO_MMAP |
> -                  SNDRV_PCM_INFO_MMAP_VALID;
> +                  SNDRV_PCM_INFO_MMAP_VALID |
> +                  SNDRV_PCM_INFO_SYNC_APPLPTR;
>  
>         /* SNDRV_PCM_INFO_BATCH */
>         hw->periods_min = 2;
> 
> Takashi Sakamoto (6):
>   pcm: hw: add a helper function to query status/control data
>   pcm: hw: add a helper function just to query status data
>   pcm: hw: add a helper function to request hwsync without side-effects
>   pcm: hw: add a helper function to issue appl_ptr without side-effects
>   pcm: hw: add a helper function to issue avail_min without side-effects
>   pcm: hw: remove superfluous code to call of SNDRV_PCM_IOCTL_SYNC_PTR
>     in snd_pcm_hw_forward()

Applied all 6 patches now.  Thanks.


Takashi