Hi Bin, Few questions:
1. If there is a leak of IOVA due to dma_unmap_* not being called somewhere then at certain point the throughput will drastically fall and will almost become equal to zero. This should be due to unavailability of the mapping anymore. But in your case VM is getting killed so this could be actual DMA buffer leak not DMA mapping leak. I doubt VM will get killed due to exhaustion of the DMA mappings in the IOMMU Layer for a transient reason or even due to mapping/unmapping leak. 2. Could you check if you have TSO offload enabled on Intel 82599? It will help in reducing the number of mappings and will take off IOVA mapping pressure from the IOMMU/VT-d? Though I am not sure it will help in reducing the amount of memory required for the buffers. 3. Also, have you checked the cpu-usage while your experiment is going on? Thanks Salil. > -----Original Message----- > From: iommu [mailto:iommu-boun...@lists.linux-foundation.org] On Behalf Of > Robin Murphy > Sent: Friday, April 24, 2020 5:31 PM > To: Bin <anole1...@gmail.com> > Cc: iommu@lists.linux-foundation.org > Subject: Re: iommu_iova slab eats too much memory > > On 2020-04-24 2:20 pm, Bin wrote: > > Dear Robin: > > Thank you for your explanation. Now, I understand that this could be > > NIC driver's fault, but how could I confirm it? Do I have to debug the > > driver myself? > > I'd start with CONFIG_DMA_API_DEBUG - of course it will chew through > memory about an order of magnitude faster than the IOVAs alone, but it > should shed some light on whether DMA API usage looks suspicious, and > dumping the mappings should help track down the responsible driver(s). > Although the debugfs code doesn't show the stacktrace of where each > mapping was made, I guess it would be fairly simple to tweak that for a > quick way to narrow down where to start looking in an offending driver. > > Robin. > > > Robin Murphy <robin.mur...@arm.com> 于2020年4月24日周五 下午8:15写道： > > > >> On 2020-04-24 1:06 pm, Bin wrote: > >>> I'm not familiar with the mmu stuff, so what you mean by "some driver > >>> leaking DMA mappings", is it possible that some other kernel module like > >>> KVM or NIC driver leads to the leaking problem instead of the iommu > >> module > >>> itself? > >> > >> Yes - I doubt that intel-iommu itself is failing to free IOVAs when it > >> should, since I'd expect a lot of people to have noticed that. It's far > >> more likely that some driver is failing to call dma_unmap_* when it's > >> finished with a buffer - with the IOMMU disabled that would be a no-op > >> on x86 with a modern 64-bit-capable device, so such a latent bug could > >> have been easily overlooked. > >> > >> Robin. > >> > >>> Bin <anole1...@gmail.com> 于 2020年4月24日周五 20:00写道： > >>> > >>>> Well, that's the problem! I'm assuming the iommu kernel module is > >> leaking > >>>> memory. But I don't know why and how. > >>>> > >>>> Do you have any idea about it? Or any further information is needed? > >>>> > >>>> Robin Murphy <robin.mur...@arm.com> 于 2020年4月24日周五 19:20写道： > >>>> > >>>>> On 2020-04-24 1:40 am, Bin wrote: > >>>>>> Hello? anyone there? > >>>>>> > >>>>>> Bin <anole1...@gmail.com> 于2020年4月23日周四 下午5:14写道： > >>>>>> > >>>>>>> Forget to mention, I've already disabled the slab merge, so this is > >>>>> what > >>>>>>> it is. > >>>>>>> > >>>>>>> Bin <anole1...@gmail.com> 于2020年4月23日周四 下午5:11写道： > >>>>>>> > >>>>>>>> Hey, guys: > >>>>>>>> > >>>>>>>> I'm running a batch of CoreOS boxes, the lsb_release is: > >>>>>>>> > >>>>>>>> ``` > >>>>>>>> # cat /etc/lsb-release > >>>>>>>> DISTRIB_ID="Container Linux by CoreOS" > >>>>>>>> DISTRIB_RELEASE=2303.3.0 > >>>>>>>> DISTRIB_CODENAME="Rhyolite" > >>>>>>>> DISTRIB_DESCRIPTION="Container Linux by CoreOS 2303.3.0 (Rhyolite)" > >>>>>>>> ``` > >>>>>>>> > >>>>>>>> ``` > >>>>>>>> # uname -a > >>>>>>>> Linux cloud-worker-25 4.19.86-coreos #1 SMP Mon Dec 2 20:13:38 -00 > >>>>> 2019 > >>>>>>>> x86_64 Intel(R) Xeon(R) CPU E5-2640 v2 @ 2.00GHz GenuineIntel > >>>>> GNU/Linux > >>>>>>>> ``` > >>>>>>>> Recently, I found my vms constently being killed due to OOM, and > >> after > >>>>>>>> digging into the problem, I finally realized that the kernel is > >>>>> leaking > >>>>>>>> memory. > >>>>>>>> > >>>>>>>> Here's my slabinfo: > >>>>>>>> > >>>>>>>> Active / Total Objects (% used) : 83818306 / 84191607 (99.6%) > >>>>>>>> Active / Total Slabs (% used) : 1336293 / 1336293 (100.0%) > >>>>>>>> Active / Total Caches (% used) : 152 / 217 (70.0%) > >>>>>>>> Active / Total Size (% used) : 5828768.08K / 5996848.72K > >>>>> (97.2%) > >>>>>>>> Minimum / Average / Maximum Object : 0.01K / 0.07K / 23.25K > >>>>>>>> > >>>>>>>> OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME > >>>>>>>> > >>>>>>>> 80253888 80253888 100% 0.06K 1253967 64 5015868K > >> iommu_iova > >>>>> > >>>>> Do you really have a peak demand of ~80 million simultaneous DMA > >>>>> buffers, or is some driver leaking DMA mappings? > >>>>> > >>>>> Robin. > >>>>> > >>>>>>>> 489472 489123 99% 0.03K 3824 128 15296K kmalloc-32 > >>>>>>>> > >>>>>>>> 297444 271112 91% 0.19K 7082 42 56656K dentry > >>>>>>>> > >>>>>>>> 254400 252784 99% 0.06K 3975 64 15900K > >> anon_vma_chain > >>>>>>>> > >>>>>>>> 222528 39255 17% 0.50K 6954 32 111264K kmalloc-512 > >>>>>>>> > >>>>>>>> 202482 201814 99% 0.19K 4821 42 38568K > >> vm_area_struct > >>>>>>>> > >>>>>>>> 200192 200192 100% 0.01K 391 512 1564K kmalloc-8 > >>>>>>>> > >>>>>>>> 170528 169359 99% 0.25K 5329 32 42632K filp > >>>>>>>> > >>>>>>>> 158144 153508 97% 0.06K 2471 64 9884K kmalloc-64 > >>>>>>>> > >>>>>>>> 149914 149365 99% 0.09K 3259 46 13036K anon_vma > >>>>>>>> > >>>>>>>> 146640 143123 97% 0.10K 3760 39 15040K buffer_head > >>>>>>>> > >>>>>>>> 130368 32791 25% 0.09K 3104 42 12416K kmalloc-96 > >>>>>>>> > >>>>>>>> 129752 129752 100% 0.07K 2317 56 9268K Acpi-Operand > >>>>>>>> > >>>>>>>> 105468 105106 99% 0.04K 1034 102 4136K > >>>>>>>> selinux_inode_security > >>>>>>>> 73080 73080 100% 0.13K 2436 30 9744K > >>>>> kernfs_node_cache > >>>>>>>> > >>>>>>>> 72360 70261 97% 0.59K 1340 54 42880K inode_cache > >>>>>>>> > >>>>>>>> 71040 71040 100% 0.12K 2220 32 8880K > >> eventpoll_epi > >>>>>>>> > >>>>>>>> 68096 59262 87% 0.02K 266 256 1064K kmalloc-16 > >>>>>>>> > >>>>>>>> 53652 53652 100% 0.04K 526 102 2104K pde_opener > >>>>>>>> > >>>>>>>> 50496 31654 62% 2.00K 3156 16 100992K > >> kmalloc-2048 > >>>>>>>> > >>>>>>>> 46242 46242 100% 0.19K 1101 42 8808K cred_jar > >>>>>>>> > >>>>>>>> 44496 43013 96% 0.66K 927 48 29664K > >>>>> proc_inode_cache > >>>>>>>> > >>>>>>>> 44352 44352 100% 0.06K 693 64 2772K > >>>>> task_delay_info > >>>>>>>> > >>>>>>>> 43516 43471 99% 0.69K 946 46 30272K > >>>>> sock_inode_cache > >>>>>>>> > >>>>>>>> 37856 27626 72% 1.00K 1183 32 37856K > >> kmalloc-1024 > >>>>>>>> > >>>>>>>> 36736 36736 100% 0.07K 656 56 2624K > >> eventpoll_pwq > >>>>>>>> > >>>>>>>> 34076 31282 91% 0.57K 1217 28 19472K > >>>>> radix_tree_node > >>>>>>>> > >>>>>>>> 33660 30528 90% 1.05K 1122 30 35904K > >>>>> ext4_inode_cache > >>>>>>>> > >>>>>>>> 32760 30959 94% 0.19K 780 42 6240K kmalloc-192 > >>>>>>>> > >>>>>>>> 32028 32028 100% 0.04K 314 102 1256K > >>>>> ext4_extent_status > >>>>>>>> > >>>>>>>> 30048 30048 100% 0.25K 939 32 7512K > >>>>> skbuff_head_cache > >>>>>>>> > >>>>>>>> 28736 28736 100% 0.06K 449 64 1796K fs_cache > >>>>>>>> > >>>>>>>> 24702 24702 100% 0.69K 537 46 17184K files_cache > >>>>>>>> > >>>>>>>> 23808 23808 100% 0.66K 496 48 15872K ovl_inode > >>>>>>>> > >>>>>>>> 23104 22945 99% 0.12K 722 32 2888K kmalloc-128 > >>>>>>>> > >>>>>>>> 22724 21307 93% 0.69K 494 46 15808K > >>>>> shmem_inode_cache > >>>>>>>> > >>>>>>>> 21472 21472 100% 0.12K 671 32 2684K seq_file > >>>>>>>> > >>>>>>>> 19904 19904 100% 1.00K 622 32 19904K UNIX > >>>>>>>> > >>>>>>>> 17340 17340 100% 1.06K 578 30 18496K mm_struct > >>>>>>>> > >>>>>>>> 15980 15980 100% 0.02K 94 170 376K avtab_node > >>>>>>>> > >>>>>>>> 14070 14070 100% 1.06K 469 30 15008K > >> signal_cache > >>>>>>>> > >>>>>>>> 13248 13248 100% 0.12K 414 32 1656K pid > >>>>>>>> > >>>>>>>> 12128 11777 97% 0.25K 379 32 3032K kmalloc-256 > >>>>>>>> > >>>>>>>> 11008 11008 100% 0.02K 43 256 172K > >>>>>>>> selinux_file_security > >>>>>>>> 10812 10812 100% 0.04K 106 102 424K > >> Acpi-Namespace > >>>>>>>> > >>>>>>>> These information shows that the 'iommu_iova' is the top memory > >>>>> consumer. > >>>>>>>> In order to optimize the network performence of Openstack virtual > >>>>> machines, > >>>>>>>> I enabled the vt-d feature in bios and sriov feature of Intel 82599 > >>>>> 10G > >>>>>>>> NIC. I'm assuming this is the root cause of this issue. > >>>>>>>> > >>>>>>>> Is there anything I can do to fix it? > >>>>>>>> > >>>>>>> > >>>>>> > >>>>>> > >>>>>> _______________________________________________ > >>>>>> iommu mailing list > >>>>>> iommu@lists.linux-foundation.org > >>>>>> https://lists.linuxfoundation.org/mailman/listinfo/iommu > >>>>>> > >>>>> > >>>> > >>> > >> > > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
