Re: [PATCH] devcoredump: increase the device delete timeout to 10 mins

[Abhinav Kumar]

Hi Greg

On 2/11/2022 11:04 PM, Greg KH wrote:
> On Fri, Feb 11, 2022 at 10:59:39AM -0800, Abhinav Kumar wrote:
> > Hi Greg
> >
> > Thanks for the response.
> >
> > On 2/11/2022 3:09 AM, Greg KH wrote:
> > > On Tue, Feb 08, 2022 at 11:44:32AM -0800, Abhinav Kumar wrote:
> > > > There are cases where depending on the size of the devcoredump and the speed
> > > > at which the usermode reads the dump, it can take longer than the current 5 mins
> > > > timeout.
> > > >
> > > > This can lead to incomplete dumps as the device is deleted once the timeout expires.
> > > >
> > > > One example is below where it took 6 mins for the devcoredump to be completely read.
> > > >
> > > > 04:22:24.668 23916 23994 I HWDeviceDRM::DumpDebugData: Opening /sys/class/devcoredump/devcd6/data
> > > > 04:28:35.377 23916 23994 W HWDeviceDRM::DumpDebugData: Freeing devcoredump node
> > >
> > > What makes this so slow?  Reading from the kernel shouldn't be the
> > > limit, is it where the data is being sent to?
> >
> > We are still checking this. We are seeing better read times when we bump up
> > the thread priority of the thread which was reading this.
>
> Where is the thread sending the data to?

The thread is writing the data to a file in local storage. From our 
profiling, the read is the one taking the time not the write.

> > We are also trying to check if bumping up CPU speed is helping.
> > But, results have not been consistently good enough. So we thought we should
> > also increase the timeout to be safe.
>
> Why would 10 minutes be better than 30?  What should the limit be?  :)

Again, this is from our profiling. We are seeing a worst case time of 7 
mins to finish the read for our data. Thats where the 10mins came from. 
Just doubling what we have currently. I am not sure how the current 5 
mins timeout came from.

> thanks,
>
> greg k-h