[ovs-dev] can not well distributed when use dp_hash for ovs group

Jan Scheurich jan.scheurich at ericsson.com
Tue Mar 20 18:19:50 UTC 2018


I just submitted v1 of the patch series to the mailing list.
Please have a look and comment.

BR, Jan

> -----Original Message-----
> From: Jan Scheurich
> Sent: Tuesday, 20 March, 2018 15:16
> To: 'ychen' <ychen103103 at 163.com>; dev at openvswitch.org; jarno at ovn.org
> Subject: RE: [ovs-dev] can not well distributed when use dp_hash for ovs group
> 
> Hi ychen,
> 
> We have been working on this problem and have a fully working patch that we will submit to the ML shortly.
> We would be glad if you could give it a test and review.
> 
> Thanks, Jan
> 
> > -----Original Message-----
> > From: ovs-dev-bounces at openvswitch.org [mailto:ovs-dev-bounces at openvswitch.org] On Behalf Of ychen
> > Sent: Tuesday, 20 March, 2018 14:20
> > To: dev at openvswitch.org; jarno at ovn.org
> > Subject: [ovs-dev] can not well distributed when use dp_hash for ovs group
> >
> > hi,
> >   I tested dp_hash for ovs group, and found that dp_hash can not well distributed, some buckets even can not be selected.
> >   In my testing environment, I have 11 buckets:
> > group_id=131841,type=select,selection_method=dp_hash,
> > bucket=bucket_id:51162,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.29:80))),
> > bucket=bucket_id:42099,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.25:80))),
> > bucket=bucket_id:53526,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.27:80))),
> > bucket=bucket_id:12221,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.40:80))),
> > bucket=bucket_id:2787,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.26:80))),
> > bucket=bucket_id:18951,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.24:80))),
> > bucket=bucket_id:32559,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.62:80))),
> > bucket=bucket_id:35550,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.43:80))),
> > bucket=bucket_id:9026,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.57:80))),
> > bucket=bucket_id:26811,weight:100,actions=ct(commit,table=70,zone=2,exec(move:NXM_OF_ETH_SRC[]-
> > >NXM_NX_CT_LABEL[0..47],nat(dst=10.204.8.34:80)))
> >
> >
> >  But about 3~5 buckets can not be selected always.
> >
> >
> >   In the function xlate_dp_hash_select_group(), I found the code:
> >   uint32_t mask = (1 << log_2_ceil(n_buckets)) - 1;
> >   uint32_t basis = 0xc2b73583 * (ctx->xin->flow.dp_hash & mask);
> > uint32_t score =  (hash_int(bucket->bucket_id, basis) & 0xffff) * bucket->weight;
> >
> >
> >  for the above formula, if n_buckets is 11, then there are totally 16 probabilities for basis.
> > so how can we make sure the best score can well distributed in the 11 buckets?
> >
> > _______________________________________________
> > dev mailing list
> > dev at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-dev


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