Re: [PATCH 9/9] IB/srp: Add fast registration support

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On 5/8/2014 3:38 PM, Bart Van Assche wrote:
On 05/07/14 19:19, Sagi Grimberg wrote:
On 5/7/2014 5:59 PM, Bart Van Assche wrote:
On 05/07/14 13:34, Sagi Grimberg wrote:
+        pool = srp_create_fr_pool(dev->dev, dev->pd,
+                      SRP_MDESC_PER_POOL, max_pages_per_mr);
1024 FRMRs per connection?! we use 1024 FMRs for all connections
(per-device). I'd say that's a major over-allocation.
It depends on how many discontiguous I/O requests are submitted
concurrently. Anyway, how about limiting the number of memory regions to
the queue size ?
Perhaps, but we will need to reserve some more for discontinuous IOs.
It is heuristic, for FS in most cases IO will align nicely, for some
crazy DB applications - I'm not sure.
If srp_map_sg() runs out of memory descriptors it adds the remaining sg
entries to the SRP indirect descriptor without using memory
registration. In other words, I think a queue full of discontiguous I/O
requests should be handled properly by srp_map_sg().

True, SRP can do without registration altogether by passing multiple SGEs, we still strive
to register memory though.

Would you consider making it configurable with default to queue_size?
This way the user which is (hopefully) aware of it's typical IO pattern can choose a suitable value.

Sagi.
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