tech-kern archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: Audio device mmap and kevents



mmap(2) may reduce copies between user space and the kernel
compared to write(2).  Generally speaking, yes.
But your patch seems to increase memcpy(3) instead of decreasing
write(2) system call.
In audioplay, well, if the audio device is mmapped 1 call to write is
replaced with 1 call to memcpy.
This is perfectly normal. write(2) probably uses memcpy(3)?
As you say, there's less copies between user space and kernel. In user
space: no more no less.

You are right in the situation where the audio file cannot be mmapped and the audio
device can. Here I do read in an intermediate buffer, which is useless.

There is clearly work to be done.


Home | Main Index | Thread Index | Old Index