[Lustre-devel] lustre-to-LNET API: big non-aligned bulk transfers

[Eric Barton <eeb@sun.com>]

Maxim,

It should support such transfers, but you have to be careful about
the number of fragments this can introduce.  This issue has already
been observed in routers, which buffer LNET message payloads at
the same page offset, irrespective of the sender's page offset (of
which it has no knowledge).  For example, this can force the o2iblnd,
if configured to pre-map all memory, to need double the number of RDMA
fragments and therefore fail the transfer.  Chat with Liang - he knows
all about this...

    Cheers,
              Eric

> -----Original Message-----
> From: lustre-devel-bounces at lists.lustre.org [mailto:lustre-devel-bounces at lists.lustre.org] On Behalf Of Maxim V.
> Patlasov
> Sent: 14 October 2009 8:23 AM
> To: lustre-devel at lists.lustre.org
> Subject: [Lustre-devel] lustre-to-LNET API: big non-aligned bulk transfers
> 
> Hi lustre-devel,
> 
> I'd like to gather some opinions about the following question:
> 
> Is it allowed or possible for lustre to submit relatively big bulk
> transfer request (e.g. >512K) to LNET layer when offset in the very
> first page to fetch bulk data from (on sender side) is not equal to the
> offset in the very first page to store data (on receiver side)? In the
> other words - should LNET support such transfers?
> 
> Thanks in advance,
> Maxim
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