> -Original Message-
> From: Dexuan Cui
> Sent: Sunday, September 6, 2015 4:48 AM
> To: Greg Kroah-Hartman ; Vitaly Kuznetsov
>
> Cc: Jiri Slaby ; linux-ser...@vger.kernel.org; linux-
> ker...@vger.kernel.org; KY Srinivasan ; Peter Hurley
>
> Subject: RE: [P
> -Original Message-
> From: Greg Kroah-Hartman
> Sent: Saturday, September 5, 2015 0:10
> On Fri, Sep 04, 2015 at 09:19:38AM +0200, Vitaly Kuznetsov wrote:
> > Greg Kroah-Hartman writes:
> >
> > > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote:
> > >> Hyper-V serial port
On Fri, Sep 04, 2015 at 09:19:38AM +0200, Vitaly Kuznetsov wrote:
> Greg Kroah-Hartman writes:
>
> > On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote:
> >> Hyper-V serial port is very slow on multi-vCPU guest, this causes
> >> soflockups on intensive console writes. Touch nmi watc
On 09/04/2015 03:19 AM, Vitaly Kuznetsov wrote:
> Greg Kroah-Hartman writes:
>> I don't like this, please narrow this down to the real problem that your
>> hardware has here, the putchar function should not be this slow. If it
>> is, something is wrong.
>
> I'm afraid this is really the case:
>
Greg Kroah-Hartman writes:
> On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote:
>> Hyper-V serial port is very slow on multi-vCPU guest, this causes
>> soflockups on intensive console writes. Touch nmi watchdog after putting
>> every char on port to avoid the issue for all serial d
On Mon, Aug 31, 2015 at 04:34:16PM +0200, Vitaly Kuznetsov wrote:
> Hyper-V serial port is very slow on multi-vCPU guest, this causes
> soflockups on intensive console writes. Touch nmi watchdog after putting
> every char on port to avoid the issue for all serial drivers, the overhead
> should be s
Peter Hurley writes:
> Hi Vitaly,
>
> On 08/31/2015 10:34 AM, Vitaly Kuznetsov wrote:
>> Hyper-V serial port is very slow on multi-vCPU guest
>
> How slow and why?
>
Not sure why, but here is a trace:
1) | serial8250_console_putchar() {
1) |
Hi Vitaly,
On 08/31/2015 10:34 AM, Vitaly Kuznetsov wrote:
> Hyper-V serial port is very slow on multi-vCPU guest
How slow and why?
> this causes
> soflockups on intensive console writes. Touch nmi watchdog after putting
> every char on port to avoid the issue for all serial drivers, the overhea
Hyper-V serial port is very slow on multi-vCPU guest, this causes
soflockups on intensive console writes. Touch nmi watchdog after putting
every char on port to avoid the issue for all serial drivers, the overhead
should be small.
This is just a part of the fix: serial8250_console_write() disables
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