Re: [RFC PATCH 0/7] Trace events to pstore

[Sai Prakash Ranjan]

On 2020-09-03 03:17, Joel Fernandes wrote:
> On Wed, Sep 2, 2020 at 4:01 PM Nachammai Karuppiah
> <nachukannan@xxxxxxxxx> wrote:
> > Hi,
> >
> > This patch series adds support to store trace events in pstore.
> >
> > Storing trace entries in persistent RAM would help in understanding 
> > what
> > happened just before the system went down. The trace events that led 
> > to the
> > crash can be retrieved from the pstore after a warm reboot. This will 
> > help
> > debug what happened before machine’s last breath. This has to be done 
> > in a
> > scalable way so that tracing a live system does not impact the 
> > performance
> > of the system.
>
> Just to add, Nachammai was my intern in the recent outreachy program
> and we designed together a way for trace events to be written to
> pstore backed memory directory instead of regular memory. The basic
> idea is to allocate frace's ring buffer on pstore memory and have it
> right there. Then recover it on reboot. Nachammai wrote the code with
> some guidance :) . I talked to Steve as well in the past about the
> basic of idea of this. Steve is on vacation this week though.
>
> This is similar to what +Sai Prakash Ranjan was trying to do sometime
> ago: https://lkml.org/lkml/2018/9/8/221 . But that approach involved
> higher overhead due to synchronization of writing to the otherwise
> lockless ring buffer.
>
> +Brian Norris has also expressed interest for this feature.

Great work Nachammai and Joel, I have few boards with warm reboot 
support and will test
this series in coming days.

Thanks,
Sai

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