Re: [dpdk-dev] very high VIRT memory usage

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 6/9/2020 1:46 PM, Burakov, Anatoly wrote:
> On 08-Jun-20 12:03 PM, Francesco wrote:
>> Hi all,
>> I upgraded an old DPDK-based app which was using DPDK 17.11 to latest DPDK
>> 20.05 and I noticed that if I look  at "top" I see that the VIRT memory
>> taken by my application is now 256.1GB while before it was <1GB.
>>
>> I've seen this same behavior with also "testpmd" example... is this a known
>> issue with latest DPDK versions?
>> Can I tweak some setting to have VIRT memory usage more or less similar to
>> RSS ?
>>
>> I forgot to add I'm working on Linux, Centos7
>>
>> Thanks,
>> Francesco Montorsi
>>
> 
> There was a discussion on this not too long ago, but i can't seem to 
> find it for some reason. 

Can it be "Big spike in DPDK VSZ" ?
http://inbox.dpdk.org/dev/CAGxAMwD6Wtfi=C2Txwjfk0zhFvRzeqBu7mFfE8ayh=EJi2aU-A@mail.gmail.com/#t

> Anyway, long story short, that's not a bug, 
> that's by design.
> 
> Since 18.11 (or 18.05 to be precise), there is a new memory subsystem in 
> DPDK that allows growing and shrinking DPDK memory usage at runtime. 
> That means, you can start with zero hugepages preallocated, and then 
> allocate as you go, letting the memory subsystem decide how much memory 
> you need.
> 
> The catch is that all of this hugepage memory is allocated into 
> somewhere, some virtual address space. And *that* address space is 
> preallocated at startup, to allow for secondary processes to duplicate 
> primary process's address space exactly, and allow dynamic allocation of 
> *shared* memory at runtime.
> 
> This memory will show up in top et al. but the truth is, it's zero cost, 
> because it's anonymous memory. It isn't actually taking up any RAM. It 
> will show up in dumps (20.05 has already fixed that issue, and the fixes 
> will probably be backported to stable, including 18.11), so unless you 
> have a very specific problem, i don't think that's anything you should 
> be concerned about.
>