Hi Anatoly, Thanks a lot for the detailed response! Good to know anyway there's a "fix" already done in 20.05... also because I'm not interested in supporting secondary processes or having shared memory...
Looking forward for the backports in stable branches then! Thanks! Francesco Il mar 9 giu 2020, 14:46 Burakov, Anatoly <anatoly.bura...@intel.com> ha scritto: > 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. 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. > > -- > Thanks, > Anatoly >
