Re: [Xen-devel] [PATCH 00/25 v7] SBSA UART emulation support in Xen

[Wei Liu <wei.liu2@xxxxxxxxxx>]

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.

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