On Mon, 11 Mar 2002, Takashi Iwai wrote:
> Hi,
>
> the current alsa driver uses ioctl for read and write pcm data.
> while writing the 32 -> 64 bit ioctl wrapper, i found that there might
> be difference between ioctl and read/write wrt the performance on
> SMP.
> sys_ioctl() calls a global lock_kernel() during ioctl operation,
> while read and write don't.
> i'm not sure whether/how this affects. did anybody investigate this
> already?
This lock is released when ioctl code calls schedule*(). We have no CPU
intensive data processing in the kernel space, so I think that this
penalty is minimal. Sure, it would be better to move such locking from
sys_ioctl to driver code.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project http://www.alsa-project.org
SuSE Linux http://www.suse.com
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