From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lennart Poettering Subject: Re: [alsa-devel] [RFC] disabling ALSA period interrupts Date: Sat, 8 May 2010 01:25:16 +0200 Message-ID: <20100507232516.GB16910@tango.0pointer.de> References: Reply-To: General PulseAudio Discussion Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: pulseaudio-discuss-bounces@mail.0pointer.de Errors-To: pulseaudio-discuss-bounces@mail.0pointer.de To: pl bossart Cc: General PulseAudio Discussion , alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org On Thu, 29.04.10 17:38, pl bossart (bossart.nospam@gmail.com) wrote: > Howdy, > When PulseAudio is used and all PCM is routed through PulseAudio > (Fedora, Meego, etc), the notion of ALSA periods isn't very useful. > PulseAudio uses a timer to refill buffers and the period interrupts > are not used at all. This patch looks very interesting and desirable. This is something have long been waiting for. I wonder how this actually relates to snd_pcm_sw_params_set_period_event() though. > So why not disable them entirely to reduce the number of wakeups? This > is possible with a number of existing DMA controllers. The simple > patch attached shows a proof-of-concept on HDAudio, it's been working > for 5 hours on my Fedora12 laptop without any glitches and powertop > does show _zero_ wakeups from the HDAudio controller (except on > startup). I am told by my colleagues working in Windows environments > that this is what's done on Vista/Windows7 btw. This isn't to say > Windows is great but that artificial generation of not-needed > interrupts is avoidable. > > There are probably some cases where you don't want this type of > behavior (broken hardware, legacy code with multiple-buffering, > disabled timer in PulseAudio), so I think it would make sense to > request the disabling of interrupts when hw_params are set, since this > is also the time when period sizes are set. I am aware that some > changes would be needed in pcm_lib.c, where all the error checks are > done. Takashi, Jaroslav, Lennart, what do you think? I am sold! Lennart -- Lennart Poettering Red Hat, Inc. lennart [at] poettering [dot] net http://0pointer.net/lennart/ GnuPG 0x1A015CC4