(restored 'CC, sorry for dropping it originally, Notes is still hard for me)
> Jason Wang <[email protected]> wrote on 01/25/2016 05:00:05 AM: > On 01/24/2016 05:00 PM, Mike Rapoport wrote: > > Hi Jason, > > > >> Jason Wang <jasowang <at> redhat.com> writes: > >> > >> Hi all: > >> > >> This series tries to add basic busy polling for vhost net. The idea is > >> simple: at the end of tx/rx processing, busy polling for new tx added > >> descriptor and rx receive socket for a while. > > There were several conciens Michael raised on the Razya's attempt to add > > polling to vhost-net ([1], [2]). Some of them seem relevant for these > > patches as well: > > > > - What happens in overcommit scenarios? > > We have an optimization here: busy polling will end if more than one > processes is runnable on local cpu. This was done by checking > single_task_running() in each iteration. So at the worst case, busy > polling should be as fast as or only a minor regression compared to > normal case. You can see this from the last test result. > > > - Have you checked the effect of polling on some macro benchmarks? > > I'm not sure I get the question. Cover letters shows some benchmark > result of netperf. What do you mean by "macro benchmarks"? Back then, when Razya posted her polling implementation, Michael had concern about the macro effect ([3]), so I was wondering if this concern is also valid for your implementation. Now, after I've reread your changes, I think it's not that relevant... > >> The maximum number of time (in us) could be spent on busy polling was > >> specified ioctl. > > Although ioctl is definitely more appropriate interface to allow user to > > tune polling, it's still not clear for me how *end user* will interact with > > it and how easy it would be for him/her. > > There will be qemu part of the codes for end user. E.g. a vhost_poll_us > parameter for tap like: > > -netdev tap,id=hn0,vhost=on,vhost_pull_us=20 Not strictly related, I'd like to give a try to polling + vhost thread sharing and polling + workqueues. Do you mind sharing the scripts you used to test the polling? Thanks, Mike. > Thanks > > > > > [1] http://thread.gmane.org/gmane.linux.kernel/1765593 > > [2] http://thread.gmane.org/gmane.comp.emulators.kvm.devel/131343 > > > > -- > > Sincerely yours, > > Mike. > > [3] https://www.mail-archive.com/[email protected]/msg109703.html
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