On Tue, 9 Jun 2020 14:39:54 +0100 "Burakov, Anatoly" <anatoly.bura...@intel.com> wrote:
> On 09-Jun-20 2:13 PM, Ferruh Yigit wrote: > > 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=eji2a...@mail.gmail.com/#t > > > > Yes, that's the one, thanks Ferruh :) > > >> 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. The one concern is for cases like cgroup memory accounting thinking the process is huge and OOM killing it.
