linux-kernel - Re: [PATCH v2 0/2] add tracepoints for nvme command submission and completion

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Date:   Tue, 16 Jan 2018 16:00:02 +0100
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     Keith Busch <keith.busch@...el.com>
Cc:     Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Hannes Reinecke <hare@...e.de>,
        Linux NVMe Mailinglist <linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH v2 0/2] add tracepoints for nvme command submission and
 completion

On Tue, Jan 16, 2018 at 07:55:55AM -0700, Keith Busch wrote:
> On Tue, Jan 16, 2018 at 03:28:19PM +0100, Johannes Thumshirn wrote:
> > Add tracepoints for nvme command submission and completion. The tracepoints
> > are modeled after SCSI's trace_scsi_dispatch_cmd_start() and
> > trace_scsi_dispatch_cmd_done() tracepoints and fulfil a similar purpose,
> > namely a fast way to check which command is going to be queued into the HW or
> > Fabric driver and which command is completed again.
> 
> I like this very much, thanks for doing this. I think you could make the
> submission trace point tighter for PCI as Hannes was suggesting since
> an MMIO write can't fail, but doesn't look as doable for FC and RDMA.

That's what I concluded as well and I wanted to have some sort of smallest
common divisor when tracing customer problems on nvme.

I think I can come up with additional tracepoints in pci/rdma/fc but these can
be added later as well and should not hold up this series.

Byte,
	Johannes
-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
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