[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 00/25 v7] SBSA UART emulation support in Xen
On Thu, Aug 10, 2017 at 03:31:57PM +0100, Julien Grall wrote: > Hi, > > On 10/08/17 14:01, Wei Liu wrote: > > On Thu, Aug 10, 2017 at 01:40:07PM +0100, Julien Grall wrote: > > > Hi Wei, > > > > > > On 10/08/17 12:40, Wei Liu wrote: > > > > 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.liu2@xxxxxxxxxx> 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.grall@xxxxxxx> > > > > > > > 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 not sure what you mean by buffer here. The interface with the guest > > > is > > > a single data register. So characters are written one by one. > > > > Yes, that's what the guest sees, but that is not necessarily what > > xenconsoled sees. > > I am a bit confused here. What are you suggesting? To send a notification I think the other email you just sent is quite close to what I would suggest. I will reply there. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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