Date: Thu, 22 Apr 2010 14:29:29 +1000 From: Andrew Reilly <areilly@bigpond.net.au> To: Roman Divacky <rdivacky@FreeBSD.org> Cc: freebsd-multimedia@freebsd.org, Alexander Best <alexbestms@wwu.de>, freebsd-current@FreeBSD.org Subject: Re: [CFT]: ClangBSD is selfhosting, we need testers now Message-ID: <20100422042929.GA79075@duncan.reilly.home> In-Reply-To: <20100421152338.GA77210@freebsd.org> References: <permail-201004211520571e86ffa800002675-a_best01@message-id.uni-muenster.de> <20100421152338.GA77210@freebsd.org>
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On Wed, Apr 21, 2010 at 05:23:38PM +0200, Roman Divacky wrote: > On Wed, Apr 21, 2010 at 05:20:57PM +0200, Alexander Best wrote: > > i might have stumbled upon a problem with clang. i've compiled a kernel from > > the clang branch using `make kernel INSTKERNNAME=clang` and booted from it. > > i'm now experiencing audio problems with mp3s and certain video files. > > playback is awfully slow and the audio output gets distorted massively. `top` > > however reports no high cpu load and `vmstat -i` doesn't report anything > > unusual either. > > > > this problem doesn't occur with a regular gcc-kernel. > > > > both kernels are running under a regular (gcc) world. > > > > i thought it might be a problem with acpi, but disabling acpi > > (hint.acpi.0.disabled=1) gives me a system freeze. > > I've heard about this problem but did not manage to reproduce that. > > can you try to bisect what file is being miscompiled? ie. compile > half of the kernel with gcc and half with clang and bisect this > way to a single file. The FreeBSD sound subsystem has a sample-rate converter built into the feeder that (from a cursory look) is probably quite carefully tweaked to be able to perform well (or at all). I've added -multimedia to the CC line, because they're the guys who are going to know the details. It's possible that some GCC-specific manifest constants are being tested-for, with sub-optimal fall-back code being run, instead. In the mean-time, Alexander, are there any sound-related sysctls that you can tweak so that the audio playback that you're doing does *not* involve sample rate conversion? Cheers, -- Andrew
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