[PATCH v1 0/3] Asynchronous shutdown interface and example implementation

[Keith Busch]

On Mon, Mar 28, 2022 at 04:00:05PM -0700, Tanjore Suresh wrote:
> Problem:
> 
> Some of our machines are configured with  many NVMe devices and
> are validated for strict shutdown time requirements. Each NVMe
> device plugged into the system, typicaly takes about 4.5 secs
> to shutdown. A system with 16 such NVMe devices will takes
> approximately 80 secs to shutdown and go through reboot.
> 
> The current shutdown APIs as defined at bus level is defined to be
> synchronous. Therefore, more devices are in the system the greater
> the time it takes to shutdown. This shutdown time significantly
> contributes the machine reboot time.
> 
> Solution:
> 
> This patch set proposes an asynchronous shutdown interface at bus level,
> modifies the core driver, device shutdown routine to exploit the
> new interface while maintaining backward compatibility with synchronous
> implementation already existing (Patch 1 of 3) and exploits new interface
> to enable all PCI-E based devices to use asynchronous interface semantics
> if necessary (Patch 2 of 3). The implementation at PCI-E level also works
> in a backward compatible way, to allow exiting device implementation
> to work with current synchronous semantics. Only show cases an example
> implementation for NVMe device to exploit this asynchronous shutdown
> interface. (Patch 3 of 3).

Thanks, I agree we should improve shutdown times. I tried a while ago, but
lost track to follow up at the time. Here's the reference, fwiw, though it
may be out of date :):

  http://lists.infradead.org/pipermail/linux-nvme/2014-May/000826.html

The above solution is similiar to how probe waits on an async domain.
Maybe pci can schedule the async shutdown instead of relying on low-level
drivers so that everyone implicitly benefits instead of just nvme? I'll
double-check if that's reasonable, but I'll look through this series too.