User Manual

Rev 2.1-1.0.6
Mellanox Technologies
85
For example, to create the VLAN tag 3 with pkey 0x8003 over that port in the eIPoIB interface
eth4, run:
4.8.4 Setting Performance Tuning
• Use 4K MTU over OpenSM. For further information, please refer to Section 8.4.1,
“File Format”, on page 150
• Use MTU for 4K (4092 Bytes):
• In UD mode, the maximum MTU value is 4092 Bytes
Make sure that all interfaces (including the guest interface and its virtual bridge) have the same MTU
value (MTU 4092 Bytes). For further information of MTU settings, please refer to the Hypervisor
User Manual.
• Tune the TCP/IP stack using sysctl (dom0/domu)
• Other performance tuning for KVM environment such as vCPU pinning and NUMA
tuning may apply. For further information, please refer to the Hypervisor User Manual.
4.9 Contiguous Pages
Contiguous Pages improves performance by allocating user memory regions over physical con-
tiguous pages. It enables a user application to ask low level drivers to allocate contiguous mem-
ory for it as part of
ibv_reg_mr.
Additional performance improvements can be reached by allocating Queue Pair (QP) and Com-
pletion Queue (CQ|) buffers to the Contiguous Pages.
To activate set the below environment variables with values of PREFER_CONTIG or CONTIG.
• For QP: MLX_QP_ALLOC_TYPE
• For CQ: MLX_CQ_ALLOC_TYPE
The following are all the possible values that can be allocated to the buffer:
#vconfig add eth4 3
#brctl addif br2 eth4.3
Default=0xffff, ipoib, mtu=5 : ALL=full;
# /sbin/sysctl_perf_tuning
Table 3 - Buffer Values
Possible Value
1
Description
ANON Use current pages ANON small ones.
Default value.
HUGE Force huge pages.
CONTIG Force contiguous pages.
PREFER_CONTIG Try contiguous fallback to ANON small pages.
PREFER_HUGE Try huge fallback to ANON small pages.