[LU-4755] ASSERTION( req->rq_reqbuf_len >= msgsize ) failed when using 4MB RPC

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.7.0, Lustre 2.5.3
• Labels: patch
• Severity: 3
• Assignee: Cliff White (Inactive)
• Reporter: Li Xi (Inactive)

Description

After ran "lctl set_param osc.*.max_pages_per_rpc=4M", we ran 4k random write test with IOR and easily hit this problem.

After some test, we found that the biggest value of msgsize is 16384 for bulk write, while req->rq_reqbuf_len is only 8192.

Issue Links

• is related to: LU-7181 Submitting random writes using 4MB RPC

Comments

[Jodi Levi (Inactive)]

Patch landed to Master.

[Cliff White (Inactive)]

The patch is failing sanity test at this time. Is it possible to submit a new patch?

[Andreas Dilger]

Actually, before I dismiss the patch to increase the request size, it is worthwhile to ask if there is any performance improvement from sending 4096 random pages in one RPC compared to 16 x 256 random pages in separate RPCs? It might even be faster to send parallel RPCs due to checksums running on separate cores and being handled in parallel on the OST. If there is no improvement from many random pages in one RPC, it is better to just limit the number of niobufs that the client sends in one RPC.

[Peter Jones]

Cliff

Could you please take care of this patch?

Thanks

Peter

[Li Xi (Inactive)]

With following patch, this problem won't be reproduced.

http://review.whamcloud.com/9599

However, I am wondering whether there is any automatic way to calculate the proper value of OST_MAXREQSIZE at compile time rather than doing guesswork or manual caculation.