The kdbuswreck [LWN.net]

The kdbuswreck

Posted Apr 22, 2015 20:33 UTC (Wed) by dlang (guest, #313)
Parent article: The kdbuswreck

Earlier in the process Linus did ask for examples of where the performance improvement claimed by kdbus actually matters.

The answers seemed to be that it doesn't for anything currently using dbus, but they want to allow other things (like streaming video) to use dbus, and that needs the increased performance.

That branch of the thread faded away a bit, but I don't think it was actually settled.

to post comments

The kdbuswreck

Posted Apr 22, 2015 22:38 UTC (Wed) by markhahn (guest, #32393) [Link] (4 responses)

Like the dodo isn't "settled". Since the answer amounts to "nothing reasonable needs the performance"...

The kdbuswreck

Posted Apr 23, 2015 8:49 UTC (Thu) by smurf (subscriber, #17840) [Link] (3 responses)

So what would you consider to be reasonable? I'd regard the ability to securely pass large amounts of data without copying them at all, let alone multiple times, to be reasonable enough in itself.

The kdbuswreck

Posted Apr 23, 2015 11:25 UTC (Thu) by mstefani (guest, #31644) [Link] (2 responses)

Isn't that functionality already in? kdbus uses memfd for that and memfd was uncontroversial and generic.

The kdbuswreck

Posted Apr 30, 2015 10:23 UTC (Thu) by metux-its (guest, #102293) [Link] (1 responses)

And even memfd isn't required for that.

Anybody heared of mmap() ? ;-o

The kdbuswreck

Posted Apr 30, 2015 20:00 UTC (Thu) by cesarb (subscriber, #6266) [Link]

> And even memfd isn't required for that. Anybody heared of mmap() ?

The point of using a memfd is that it can be sealed, so there's no risk of a TOCTOU vulnerability in the receiver.

With mmap(), the sender can change what the receiver sees while the receiver is looking at it.

The kdbuswreck

Posted Apr 22, 2015 23:42 UTC (Wed) by BenHutchings (subscriber, #37955) [Link] (1 responses)

I believe the predecessor of kdbus, AF_BUS, was implemented for Genivi and is being used in real IVI systems that have a high D-Bus message rate.

The kdbuswreck

Posted Apr 23, 2015 12:41 UTC (Thu) by daniels (subscriber, #16193) [Link]

> I believe the predecessor of kdbus, AF_BUS, was implemented for Genivi and is being used in real IVI systems that have a high D-Bus message rate.

Yes, and provided very real speedups. Greg linked these a couple of times.