Messages in this thread |  | | Date | Mon, 21 May 2001 17:51:08 -0400 (EDT) | From | Alexander Viro <> | Subject | Re: [RFD w/info-PATCH] device arguments from lookup, partion code |
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On Mon, 21 May 2001, Alan Cox wrote:
> > Which, BTW, is a wonderful reason for having multiple channels. Instead > > of write(fd, "critical_command", 8); read(fd,....); you read from the right fd. > > Opened before you enter the hotspot. Less overhead than ioctl() would > > have... > > The ioctl is one syscall, the read/write pair are two. Im not sure that ioctl > is going to be more overhead there. In the video4linux case the high overhead > is acking frames received by mmap so might conceivably be considered one way
Sure. But we have to do two syscalls only if ioctl has both in- and out- arguments that way. Moreover, we are talking about non-trivial in- arguments. How many of these are in hotspots?
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