Re: [SPDK] Problem with Blobstore when write 65MB continously

[Zhengyu Zhang <freeman.zhang1992 at gmail.com>]

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Hi Paul

Thanks for your reply!


On 1/10/18 11:18 PM, Luse, Paul E wrote:
> So what’s happening here is internally within Blobstore when
> _spdk_blob_request_submit_op() tries to get a channel->req via
> spdk_bs_batch_open() for a write (bear the end) it doesn’t have any
> available so returns NULL which results in a callback error of –ENOMEM
> to the hello_blob callback.  The default number of channel reqs is 512
> and the hello_blob app doesn’t change that and uses a single channel for
> submitting the 520 back to back write requests that you are issuing and
> this failure happens right there towards the end.
> 

So you are suggesting me to tune the number of channel reqs or using
multiple channels if I want to write more?

> 
> Ben, if I crank up the max channel reqs this works OK.  I’m thinking
> this shouldn’t be needed and wondering why we aren’t placing completed
> channel reqs back on the list fast enough (if that’s the real problem).
> Something to do with this being a malloc backend maybe?  Would try
> w/nvme but my dev system isn’t quite ready for prime time yet after
> reblasting it….
> 
>

I tested on both malloc backend and an P3700 NVMe SSD. Their results are
the same.

Thanks!
Zhengyu