[SPDK] Submitting NVME I/O write req with SGL

[SPDK] Submitting NVME I/O write req with SGL

[Filip Janiszewski]

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Hi,

I've plenty of 64B buffers to write to disk, but I'm having trouble
triggering the proper spdk_nvme_ns_cmd_writev_with_md to do that - I was
trying to use as sample code the 'perf' test application and the
following patch: https://gerrithub.io/c/spdk/spdk/+/437905 , but I keep
getting errors like:

.
[2021-01-29 11:17:46.573755] nvme_ns_cmd.c:
268:_nvme_ns_cmd_split_request_prp: *ERROR*: child_length 64 not even
multiple of lba_size 512
.

So I've a couple of questions:

1) Is is possible to submit NVME IO write requests while the buffers are
smaller than LBA using SGL or something?

2) Is there any documentation for that?

3) Will this work only with FIO? (the FIO plugin seems to do that, not
sure).

Obviously I can't just merge my buffers info LBA size blocks as that
would mean copy memory, I can't effort to copy memory and I need to dump
those buffers to disk.. (Wasting an entire LBA of 512B for each single
64B buffer while work is not acceptable due to disk space waste..)

Thanks

-- 
BR, Filip
+48 666 369 823