On Thu, Aug 10, 2017 at 01:29:04PM +0530, Bhupinder Thakur wrote: > Hi Wei, > > On 9 August 2017 at 16:33, Wei Liu <wei.l...@citrix.com> wrote: > > On Wed, Aug 09, 2017 at 04:28:14PM +0530, Bhupinder Thakur wrote: > >> Hi Julien, > >> > >> Thanks for the testing. > >> > >> On 8 August 2017 at 21:29, Julien Grall <julien.gr...@arm.com> wrote: > >> > Hi Bhupinder, > >> > > >> > I gave another and I have a couple of comments. > >> > > >> > Booting Linux with earlycon enabled take quite a while. I can see the > >> > characters coming slower than on the minitel. It seems to be a bit better > >> > after switching off the bootconsole. Overall Linux is taking ~20 times to > >> > boot with pl011 vs HVC console. > >> > > >> > I do agree that pl011 is emulated and therefore you have to trap after > >> > each > >> > character. But 20 times sounds far too much. > >> > > >> I think this slowness could be due to ratelimiting of the pl011 events > >> in xenconosle. Currently, the rate limit is > >> set to 30 events per 200 msecs (see > >> RATE_LIMIT_ALLOWANCE/RATE_LIMIT_PERIOD). > >> > >> I increased the rate limit to 600 events (30 * 20) per 200 msecs. With > >> this change, > >> I see that the the find command is running faster and smoother. > >> Earlier the find output would be jerky. > > > > Please consider batching the events instead of bumping the limit. > > If I try to batch the events then it may delay per character > processing (if no further characters are coming) since we will wait > for more events to come to batch them together. By keeping the rate > limit high, it is ensured that it can handle large burst of events. If > there is sporadic data then the rate limit is not hit.
But do you really need to send an event for every character (that's my reading of your patch, please correct me if I'm wrong)? Suppose you have a buffer you can send one event when the buffer is processed. > > I am thinking of making the rate limit configuration per console. > There is the question why vuart is special with regard to other types of console. If something is mandated by the spec it should be specifically called out to justify the decision to bump the rate limit. > Regards, > Bhupinder _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
