Hi Dmitry,

The biggest drop-off seems to be from size 128K to 256K. Are you using 1GB
huge pages already (rather than 2MB)?

I would think that it would not use over 1GB until you ask for 512K mbufs
or more.

--
Regards,
Robert



On Thu, Sep 19, 2013 at 3:50 AM, Dmitry Vyal [off-list ref] wrote:

Good day everyone,

While working on IP packet defragmenting I had to enlarge mempool size. I
did this to provide large enough time window for assembling a fragment
sequence. Unfortunately, I got a performance regression: if I enlarge
mempool size from 2**12 to 2**20 MBufs, packet performance for not
fragmented packets drops from ~8.5mpps to ~5.5mpps for single core. I made
only a single measure, so the data are noisy, but the trend is evident:
SIZE 4096 - 8.47mpps
SIZE 8192 - 8.26mpps
SIZE 16384 - 8.29mpps
SIZE 32768 - 8.31mpps
SIZE 65536 - 8.12mpps
SIZE 131072 - 7.93mpps
SIZE 262144 - 6.22mpps
SIZE 524288 - 5.72mpps
SIZE 1048576 - 5.63mpps

And I need even larger sizes.

I want to ask for an advice, how best to tackle this? One way I'm thinking
about is to make two mempools, one large for fragments (we may accumulate a
big number of them) and one small for full packets, we just forward them
burst by burst. Is it possible to configure RSS to distribute packets
between queues according to this scheme? Perhaps, there are better ways?

Thanks,
Dmitry