Il 08/02/2013 11:20, Luigi Rizzo ha scritto: > On Fri, Feb 8, 2013 at 2:02 AM, Stefan Hajnoczi <stefa...@gmail.com > <mailto:stefa...@gmail.com>> wrote: > > On Wed, Feb 06, 2013 at 03:23:41PM +0100, Luigi Rizzo wrote: > > The following patch implements interrupt moderation registers > > for the e1000 adapter. These feature is normally used by OS > > drivers, and their implementation improves performance significantly, > > especially on the transmit path. > > The feature can be disabled through a command line option. > > We have seen only benefits in throughput, while latency slightly > > increases (that is an inherent feature of interrupt moderation) > > because very short delays cannot be emulated precisely. > > > > For those curious on performance, there is a set of measurements > > (of this and other changes that we will post separately) at > > > > http://info.iet.unipi.it/~luigi/research.html#qemu > > http://info.iet.unipi.it/~luigi/papers/20130206-qemu.pdf is 404. > > > sorry, fixed now. > And, will resubmit a fixed patch with uninit and fixed braces in the > if() statement. > > I am happy to make this default to off. But it would be good if you could > actually give it a try. Note that linux and FreeBSD (and presumably windows) > do use moderation by default so enabling the emulation of the > registers makes the guest OS behave differently (and closer to bare metal). > > To test that the patch itself does not cause regression in the emulator > one should also turn off moderation in the guest (one of the tests i > have run).
I think making the default on is fine, but you need to add compatibility options to leave it off in older machine types (pc-1.4 and earlier). Paolo
