Re: Need help with reducing VIRT memory

[Bruce Richardson <bruce.richardson@intel.com>]

On Fri, May 03, 2024 at 02:48:12PM +0000, Lombardo, Ed wrote:
> Hi Dmitry,
> I am not clear on the DPDK memory layout and how to tweak these #define values.  
> 
> #define RTE_MAX_MEMSEG_PER_LIST 8192
> #define RTE_MAX_MEM_MB_PER_LIST 32768
> #define RTE_MAX_MEMSEG_PER_TYPE 32768
> #define RTE_MAX_MEM_MB_PER_TYPE 65536
> 
> I want to limit how much DPDK grabs for memory, but grabs what it absolutely needs for our application.

Hi,

This is what DPDK does. What is being shown in the VIRT figures is the
address space reservation DPDK has made, but not what memory it actually uses.
Only sufficient hugepage memory to meet the demands of your app should be
mapped by DPDK, the rest is unused address space that is not taking up any
actual memory.

Adding Anatoly to the thread, as he is probably best able to suggest what
settings above to tweak to reduce this address-space allocation if it is a
problem for you. If it is an issue, I'd be curious to know what the
underlying cause is, in case there is something we need to fix.

/Bruce

>  I don't want DPDK to plan for any hot-plug or dynamic adjustments of hugepages.  Our configuration is static, we allocate hugepages, discover ports and initialize couple ring buffers and 1 Rx Q and 4 Tx Qs per port.  Max of 4 ports.
> My goal is to reduce our application VIRT memory by 80%.  Not clear which config variables to adjust.
> 
> What do you suggest, is there a formula?
> 
> Regards,
> Ed
>