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<div class="moz-cite-prefix">On 01/14/2015 12:11 AM, Anand Avati
wrote:<br>
</div>
<blockquote
cite="mid:CAFboF2w_LPXXPzBfX8NFkP4eNrLgQTorvcMORqcO9ipm+eFqSg@mail.gmail.com"
type="cite">3) Why not have a separate iobuf pool for RDMA?<br>
</blockquote>
<br>
Since every fops are using the default iobuf_pool, if we go with
another iobuf_pool dedicated to rdma, we need to copy that buffer
from default pool to rdma or so, unless we are intelligently
allocating the buffers based on the transport which we are going to
use. It is an extra level copying in the I/O path.<br>
<br>
<blockquote
cite="mid:CAFboF2w_LPXXPzBfX8NFkP4eNrLgQTorvcMORqcO9ipm+eFqSg@mail.gmail.com"
type="cite"><br>
<div class="gmail_quote">On Tue Jan 13 2015 at 6:30:09 AM Mohammed
Rafi K C <<a moz-do-not-send="true"
href="mailto:rkavunga@redhat.com">rkavunga@redhat.com</a>>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Hi All,<br>
<br>
When using RDMA protocol, we need to register the buffer which
is going<br>
to send through rdma with rdma device. In fact, it is a costly<br>
operation, and a performance killer if it happened in I/O
path. So our<br>
current plan is to register pre-allocated iobuf_arenas from
iobuf_pool<br>
with rdma when rdma is getting initialized. The problem comes
when all<br>
the iobufs are exhausted, then we need to dynamically allocate
new<br>
arenas from libglusterfs module. Since it is created in
libglusterfs, we<br>
can't make a call to rdma from libglusterfs. So we will force
to<br>
register each of the iobufs from the newly created arenas with
rdma in<br>
I/O path. If io-cache is turned on in client stack, then all
the<br>
pre-registred arenas will use by io-cache as cache buffer. so
we have to<br>
do the registration in rdma for each i/o call for every
iobufs,<br>
eventually we cannot make use of pre registered arenas.<br>
<br>
To address the issue, we have two approaches in mind,<br>
<br>
1) Register each dynamically created buffers in iobuf by
bringing<br>
transport layer together with libglusterfs.<br>
<br>
2) create a separate buffer for caching and offload the data
from the<br>
read response to the cache buffer in background.<br>
<br>
If we could make use of preregister memory for every rdma
call, then we<br>
will have approximately 20% increment for write and 25% of
increment for<br>
read.<br>
<br>
Please give your thoughts to address the issue.<br>
<br>
Thanks & Regards<br>
Rafi KC<br>
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</blockquote>
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</blockquote>
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