Messages in this thread | | | Date | Thu, 1 Aug 2002 12:30:11 +0200 | From | Pavel Machek <> | Subject | Re: [rfc] aio-core for 2.5.29 (Re: async-io API registration for 2.5.29) |
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Hi!
> > > Can you point me out to a patch with the new cancellation API that you > > > agree with for merging in 2.5 so I can synchronize? I'm reading your > > > very latest patch loaded on some site in June. that will be really > > > helpful, many thanks! > > > > Here is what I've got for the aio core that has the cancellation > > change to return the completion event. The other slight change that > > I meant to get in before going into the mainstream is to have the > > timeout io_getevents takes be an absolute timeout, which helps for > > applications that have specific deadlines they are attempting to > > schedule to (think video playback). This drop is untested, but I'd > > are you sure this is a good idea? this adds an implicit gettimeofday > (thought no entry/exit kernel) to every getevents syscall with a > "when" specificed, so the user may now need to do gettimeofday both > externally and internally to use the previous "timeout" feature (given > the kernel can delay only of a timeout, so the kernel has to calculate > the timeout internally now). I guess I prefer the previous version that > had the "timeout" information instead of "when". Also many soft > multimedia only expect the timeout to take "timeout", and if a frame > skips they'll just slowdown the frame rate, so they won't be real time > but you'll see something on the screen/audio. Otherwise they can keep > timing out endlessy if they cannot keep up with the stream, and they > will show nothing rather than showing a low frame rate. > > So I'm not very excited about this change, I would prefer the previous > version. Also consider with the vsyscall doing the gettimeofday > calculation in userspace based on "when" rather than in-kernel isn't > going to be more expensive than your new API even of applications that > really want the "when" behaviour instead of the "timeout". While the > applications that wants the "timeout" this way we'll be forced to a > vgettimeofday in userspace and one in kernel which is a pure overhead > for them.
I believe Linus actually explained why "when" looks way better to him than "timeout". [It does not skew, for example.] Pavel -- I'm pavel@ucw.cz. "In my country we have almost anarchy and I don't care." Panos Katsaloulis describing me w.r.t. patents at discuss@linmodems.org - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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