On 2/18/18 2:47 PM, Matt Benjamin wrote:
On Fri, Feb 16, 2018 at 11:23 AM, William Allen Simpson
But the planned 2.7 improvements are mostly throughput related, not IOPS.
Not at all, though I am trying to ensure that we get async FSAL ops
in. There are people working on IOPs too.
async FSAL ops are not likely to further improve IOPS.
As I've pointed out many times in the past, async only allows
the same number of threads to handle more concurrent operations.
But it's actually slower. It basically doubles the number of
system calls. System calls are one of the reasons that Ganesha is
slower than knfsd. It also ruins CPU cache coherency.
If we're CPU bound or network bandwidth constrained, it won't help.
The effort that I've been waiting for *3* years -- add io vectors to
the FSAL interface, so that we can zero-copy buffers -- is more
likely to improve throughput.
Moreover, going through the code and removing locking other such
bottlenecks is more likely to improve IOPS.
If Ganesha is adding 6 ms to every read operation, we have a serious
problem, and need to profile immediately!
That's kind of what our team is doing. I look forward to your work
with rpc-ping-mt.
Well, you were able to send me a copy after 6 pm on a Friday, so I'm
now taking a look at it. Hopefully I'll have something by Friday.
But I really wish you'd posted it 3 years ago. It doesn't really test
IOPS, other than whatever bandwidth limit is imposed by the interface,
but it does test the client call interface.
We've been using Jeff Layton's delegation callback work to test, and
this test would have been better and easier.
But a unit test is not what we need. I wrote "profile". We need to
know where the CPU bottlenecks are in Ganesha itself.
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