On Thu, Dec 18, 2014 at 9:03 PM, Ananyev, Konstantin < konstantin.ananyev at intel.com> wrote:
> > > > -----Original Message----- > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Ananyev, Konstantin > > Sent: Thursday, December 18, 2014 5:43 PM > > To: Newman Poborsky; dev at dpdk.org > > Subject: Re: [dpdk-dev] rte_mempool_create fails with ENOMEM > > > > Hi > > > > > -----Original Message----- > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Newman Poborsky > > > Sent: Thursday, December 18, 2014 1:26 PM > > > To: dev at dpdk.org > > > Subject: [dpdk-dev] rte_mempool_create fails with ENOMEM > > > > > > Hi, > > > > > > could someone please provide any explanation why sometimes mempool > creation > > > fails with ENOMEM? > > > > > > I run my test app several times without any problems and then I start > > > getting ENOMEM error when creating mempool that are used for packets. > I try > > > to delete everything from /mnt/huge, I increase the number of huge > pages, > > > remount /mnt/huge but nothing helps. > > > > > > There is more than enough memory on server. I tried to debug > > > rte_mempool_create() call and it seems that after server is restarted > free > > > mem segments are bigger than 2MB, but after running test app for > several > > > times, it seems that all free mem segments have a size of 2MB, and > since I > > > am requesting 8MB for my packet mempool, this fails. I'm not really > sure > > > that this conclusion is correct. > > > > Yes,rte_mempool_create uses rte_memzone_reserve() to allocate > > single physically continuous chunk of memory. > > If no such chunk exist, then it would fail. > > Why physically continuous? > > Main reason - to make things easier for us, as in that case we don't > have to worry > > about situation when mbuf crosses page boundary. > > So you can overcome that problem like that: > > Allocate max amount of memory you would need to hold all mbufs in worst > case (all pages physically disjoint) > > using rte_malloc(). > > Actually my wrong: rte_malloc()s wouldn't help you here. > You probably need to allocate some external (not managed by EAL) memory in > that case, > may be mmap() with MAP_HUGETLB, or something similar. > > > Figure out it's physical mappings. > > Call rte_mempool_xmem_create(). > > You can look at: app/test-pmd/mempool_anon.c as a reference. > > It uses same approach to create mempool over 4K pages. > > > > We probably add similar function into mempool API > (create_scatter_mempool or something) > > or just add a new flag (USE_SCATTER_MEM) into rte_mempool_create(). > > Though right now it is not there. > > > > Another quick alternative - use 1G pages. > > > > Konstantin > Ok, thanks for the explanation. I understand that this is probably an OS question more than DPDK, but is there a way to again allocate a contiguous memory for n-th run of my test app? It seems that hugepages get divded/separated to individual 2MB hugepage. Shouldn't OS's memory management system try to group those hupages back to one contiguous chunk once my app/process is done? Again, I know very little about Linux memory management and hugepages, so forgive me if this is a stupid question. Is rebooting the OS the only way to deal with this problem? Or should I just try to use 1GB hugepages? p.s. Konstantin, sorry for the double reply, I accidentally forgot to include dev list in my first reply :) Newman > > > > > > > Does anybody have any idea what to check and how running my test app > > > several times affects hugepages? > > > > > > For me, this doesn't make any since because after test app exits, > resources > > > should be freed, right? > > > > > > This has been driving me crazy for days now. I tried reading a bit more > > > theory about hugepages, but didn't find out anything that could help > me. > > > Maybe it's something else and completely trivial, but I can't figure it > > > out, so any help is appreciated. > > > > > > Thank you! > > > > > > BR, > > > Newman P. >
