Memory is generally allocated in chunks of 4KB (called pages)
HugePages are memory chunks that are bigger than the default 4KB pages, such as 2MB.
When a CPU looks up pages, it will first inspect TLB cache
TLB can be accessed extremely fast
TLB cache has a limited number of entries for pages.
By increasing the size of the pages, we can use the TLB cache in a more efficient way.
4KB * 256 = 1024KB = 1MB
2MB * 256 = 512MB = 0.5GB
Increase by factor of 512.
HugePages always stay in memory and cannot be swapped. Thus, as soon as HugePages get allocated they are not available to the overall system anymore, although they might not be used at the moment.
HugePages are always allocated by the free memory of the system, which can be less than the total available memory. However not all free memory can be allocated as HugePages there will always be a remains.
Troubleshoot : show system memory
Troubleshoot : show system mem-info
Troubleshoot : VM domain XML
For a VM to use HugePages, one must ensure that the XML extract depicted below is included inside the VM domain XML.
If DPDK is enabled each newly deployed VM should include it. If this is not the case, check /var/log/esc/forever.log for any dpdk-related errors.
Troubleshoot : network xml
vNIC on network which is on service-bridge will have following configuration. Here vnic2 is on test-net, which belongs to service-bridge test-br. Notice though, the configuration doesn’t have any reference of test-br.
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