Re: [LSF/MM/BFP ATTEND] [LSF/MM/BFP TOPIC] Storage: add blktrace extension support

[Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>]

Adding Damien to this thread.
On 12/10/2019 10:17 PM, Chaitanya Kulkarni wrote:
> Hi,
>
> * Background:-
> -----------------------------------------------------------------------
>
> Linux Kernel Block layer now supports new Zone Management operations
> (REQ_OP_ZONE_[OPEN/CLOSE/FINISH] [1]).
>
> These operations are added mainly to support NVMe Zoned Namespces
> (ZNS) [2]. We are adding support for ZNS in Linux Kernel Block layer,
> user-space tools (sys-utils/nvme-cli), NVMe driver, File Systems,
> Device-mapper in order to support these devices in the field.
>
> Over the years Linux kernel block layer tracing infrastructure
> has proven to be not only extremely useful but essential for:-
>
> 1. Debugging the problems in the development of kernel block drivers.
> 2. Solving the issues at the customer sites.
> 3. Speeding up the development for the file system developers.
> 4. Finding the device-related issues on the fly without modifying
>      the kernel.
> 5. Building white box test-cases around the complex areas in the
>      linux-block layer.
>
> * Problem with block layer tracing infrastructure:-
> -----------------------------------------------------------------------
>
> If blktrace is such a great tool why we need this session for ?
>
> Existing blktrace infrastructure lacks the number of free bits that are
> available to track the new trace category. With the addition of new
> REQ_OP_ZONE_XXX we need more bits to expand the blktrace so that we can
> track more number of requests.
>
> * Current state of the work:-
> -----------------------------------------------------------------------
>
> RFC implementations [3] has been posted with the addition of new IOCTLs
> which is far from the production so that it can provide a basis to get
> the discussion started.
>
> This RFC implementation provides:-
> 1. Extended bits to track new trace categories.
> 2. Support for tracing per trace priorities.
> 3. Support for priority mask.
> 4. New IOCTLs so that user-space tools can setup the extensions.
> 5. Ability to track the integrity fields.
> 6. blktrace and blkparse implementation which supports the above
>      mentioned features.
>
> Bart and Martin has suggested changes which I've incorporated in the RFC
> revisions.
>
> * What we will discuss in the proposed session ?
> -----------------------------------------------------------------------
>
> I'd like to propose a session for Storage track to go over the following
> discussion points:-
>
> 1. What is the right approach to move this work forward?
> 2. What are the other information bits we need to add which will help
>      kernel community to speed up the development and improve tracing?
> 3. What are the other tracepoints we need to add in the block layer
>      to improve the tracing?
> 4. What are device driver callbacks tracing we can add in the block
>      layer?
> 5. Since polling is becoming popular what are the new tracepoints
>      we need to improve debugging ?
>
>
> * Required Participants:-
> -----------------------------------------------------------------------
>
> I'd like to invite block layer, device drivers and file system
> developers to:-
>
> 1. Share their opinion on the topic.
> 2. Share their experience and any other issues with blktrace
>      infrastructure.
> 3. Uncover additional details that are missing from this proposal.
>
> Regards,
> Chaitanya
>
> References :-
>
> [1] https://www.spinics.net/lists/linux-block/msg46043.html
> [2] https://nvmexpress.org/new-nvmetm-specification-defines-zoned-
> namespaces-zns-as-go-to-industry-technology/
> [3] https://www.spinics.net/lists/linux-btrace/msg01106.html
>       https://www.spinics.net/lists/linux-btrace/msg01002.html
>       https://www.spinics.net/lists/linux-btrace/msg01042.html
>       https://www.spinics.net/lists/linux-btrace/msg00880.html
>


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