This email to the SPDK list is a follow-on to a brief discussion held during a recent SPDK community meeting (Tue Jun 26 UTC 15:00).
Lifted and edited from the Trello agenda item (https://trello.com/c/U291IBYx/91-best-practices-on-driver-binding-for-spd... <https://trello.com/c/U291IBYx/91-best-practices-on-driver-binding-for-spd...>):
During development many (most?) people rely on the run of SPDK's scripts/setup.sh to perform a number of initializations, among them the unbinding of the Linux kernel nvme driver from NVMe controllers targeted for use by the SPDK and then binding them to either uio_pci_generic or vfio-pci. This script is applicable for development environments, but not targeted for use in productions systems employing the SPDK.
I'd like to confer with my fellow SPDK community members on ideas, suggestions and best practices for handling this driver unbinding/binding. I wrote some udev rules along with updates to some other Linux system conf files for automatically loading either the uio_pci_generic or vfio-pci modules. I also had to update my initramfs so that when the system comes all the way up, the desired NVMe controllers are already bound to the needed driver for SPDK operation. And, as a bonus, it should "just work" when a hotplug occurs as well. However, there may be additional considerations I might have overlooked on which I'd appreciate input. Further, there's the matter of how and whether to semi-automate this configuration via some kind of script and how that might vary according to Linux distro to say nothing of the determination of employing uio_pci_generic vs vfio-pci.
And, now some details:
1. I performed this on an Oracle Linux (OL) distro. I’m currently unaware how and what configuration files might be different depending on the distro. Oracle Linux is RedHat-compatible, so I’m confident my implementation should run similarly on RedHat-based systems, but I’ve yet to delve into other distro’s like Debian, SuSE, etc.
2. In preparation to writing my own udev rules, I unbound a specific NVMe controller from the Linux nvme driver by hand. Then, in another window I launched: "udevadm monitor -k -p” so that I could observe the usual udev events when a NVMe controller is bound to the nvme driver. On my system, I observed four (4) udev kernel events (abbreviated/edited output to avoid this become excessively long):
KERNEL[382128.187273] add /devices/pci0000:00/0000:00:02.2/0000:30:00.0/nvme/nvme0 (nvme)
KERNEL[382128.244658] bind /devices/pci0000:00/0000:00:02.2/0000:30:00.0 (pci)
KERNEL[382130.697832] add /devices/virtual/bdi/259:0 (bdi)
KERNEL[382130.698192] add /devices/pci0000:00/0000:00:02.2/0000:30:00.0/nvme/nvme0/nvme0n1 (block)
3. My udev rule triggers on (Event 2) above: the bind action. Upon this action, my udev rule appends operations to the special udev RUN variable such that udev will essentially mirror that which is done in the SPDK’s scripts/setup.sh for unbinding from the nvme driver and binding to, in my case, the vfio-pci driver.
4. With my new udev rules in place, I was successful getting specific NVMe controllers (based on bus-device-function) to unbind from the Linux nvme driver and bind to vfio-pci. However, I made a couple of observations in the kernel log (dmesg). In particular, I was drawn to the following for an NVMe controller at BDF: 0000:40:00.0 for which I had a udev rule to unbind from nvme and bind to vfio-pci:
[ 35.534279] nvme nvme1: pci function 0000:40:00.0
[ 37.964945] nvme nvme1: failed to mark controller live
[ 37.964947] nvme nvme1: Removing after probe failure status: 0
One theory I have for the above is that my udev RUN rule was invoked while the nvme driver’s probe() was still running on this controller, and perhaps the unbind request came in before the probe() completed hence this “name1: failed to mark controller live”. This has left lingering in my mind that maybe instead of triggering on (Event 2) when the bind occurs, that perhaps I should instead try to derive a trigger on the “last" udev event, an “add”, where the NVMe namespace’s are instantiated. Of course, I’d need to know ahead of time just how many namespaces exist on that controller if I were to do that so I’d trigger on the last one. I’m wondering if that may help to avoid what looks like a complaint during the middle of probe() of that particular controller. Then, again, maybe I can just safely ignore that and not worry about it at all? Thoughts?
I discovered another issue during this experimentation that is somewhat tangential to this task, but I’ll write a separate email on that topic.
thanks for any feedback,
There has been a rash of failures on the test pool starting last night. I was able to root cause the failures to a point in the NVMe-oF shutdown tests. The main substance of the failure is that QAT and the DPDK framework don't always play well with secondary dpdk processes. In the interest of avoiding these failures on future builds, please rebase your changes on the following patch series which includes the fix of not running bdevperf as a secondary process in the NVMe-oF shutdown tests.
I was out of town last week and missed the meeting but saw on Trello you had the topic below:
"a few idea: log structured data store , data store with compression, and metadata replication of Blobstore"
Which I'd be pretty interested in working on with you or at least hearing more about it. When you get a chance, no hurry, can you please expand a little on how the conversation went and what you're looking at specifically?
I have submitted the py-spdk code on https://review.gerrithub.io/#/c/379741/, please take some time to visit it, I will be very grateful to you.
The py-spdk is client which can help the upper-level app to communicate with the SPDK-based app (such as: nvmf_tgt, vhost, iscsi_tgt, etc.). Should I submit it into the other repo I rebuild rather than SPDK repo? Because I think it is a relatively independent kit upon the SPDK.
If you have some thoughts about the py-spdk, please share with me.
I'm SPDK core maintainer responsible for the vhost library.
I saw your virtio-vhost-user patch series on gerrithub. I know you've
been talking about it on SPDK community meeting over a month ago,
although I was on holiday at that time.
I wanted to give you some background of what is currently going on
around SPDK vhost.
SPDK currently keeps an internal copy of DPDK's rte_vhost with a
couple of storage specific changes. We have tried to upstream those
changes to DPDK, but they were rejected . Although they were
critical to support vhost-scsi or vhost-blk, they also altered how
vhost-net operated and that was DPDK's major concern. We kept the
internal rte_vhost copy but still haven't decided whether to try to
switch to DPDK's version or to completely derive from DPDK and
maintain our own vhost library. At one point we've also put together a
list of rte_vhost issues - one of which was vhost-user specification
incompliance that eventually made our vhost-scsi unusable with QEMU
2.12+. The amount of "fixes" that rte_vhost required was huge.
Instead, we tried to create a new, even lower level vhost library in
DPDK . The initial API proposal was warmly welcomed , but a few
months later, after a PoC implementation was ready, the whole library
was rejected as well . [One of the concerns the new library would
address was creating an abstraction and environment for
virtio-vhost-user, but apparently DPDK team didn't find that useful at
We still have the rte_vhost copy in SPDK and we still haven't decided
on its future strategy, which is why we were so reluctant to reviewing
Just last week we seem to have finally made some progress, as a DPDK
patch that would potentially allow SPDK to use DPDK's rte_vhost
directly  was approved for DPDK 19.05. Around the end of February I
believe SPDK will try to stop using its rte_vhost copy and switch to
DPDK's rte_vhost with the mentioned patch.
After that happens, I would like to ask you to rebase your patches on
latest DPDK's rte_vhost and resubmit them to DPDK. I can certainly
help with upstreaming vfio no-iommu support in SPDK and am even
willing to implement registering non-2MB-aligned memory, but rte_vhost
changes belong in DPDK.
I'm sorry for the previous lack of transparency in this matter.
I am looking for using spdk_threads with a custom scheduler as presented by Ben in the recent summit. I understand that I can do that by calling spdk_thread_poll from within my scheduler's poller. But I see that there are thread local variables used by various modules (such as bdev) which wont work if I move my poller to a different core. One example is spdk_bdev_open which gets spdk_thread from the tls variable. Thoughts/ideas ?
On behalf of the SPDK community I'm pleased to announce the release of SPDK 19.04!
This release contains the following new features:
- Compression bdev: Added "reduce" block compression scheme based on using SSDs for storing compressed blocks of storage and persistent memory for metadata.
- Notification: Added the notify library that provides a high performance local event bus between libraries. Example usage was added to bdev module, which reports notifications for added and removed bdevs via RPC.
- NVMe: Opal support was added for scan, take ownership, revert TPer, and dumping device info. The nvme_manage tool can be used to perform these operations.
- OCF: Added support for caching multiple bdevs using a single bdev as a cache.
- DIF pass-through in the NVMe-oF target: DIF setting of the allocated bdevs can be exposed to the NVMe-oF initiator and data with DIF from the NVMe-oF initiator can be passed through to the allocated bdevs.
- vhost: Added experimental support for running with the external, upstream rte_vhost library.
The full changelog for this release is available at:
This release contains 870 commits from 57 authors with over 34k lines of code changed. We'd especially like to say thank you to all of our first time contributors:
Claire J. In
Thanks to everyone for your contributions, participation, and effort!
Hi Ben and Darek,
Quick question on your presentation at the last SPDK Summit.
“Available on Cascade Lake N SKUs” on “Flexible and dynamic resource use
I’m confused as I found Y SKUs are supporting SST instead of N SKUs.
Please make sure which SKU is required for SPDK dynamic threading.
first I want to say that I really enjoyed all the great presentations and
the conversations at the SPDK Summit! A conference like that is really
I'm currently looking into integrating SPDK (mainly nvme-of) into an
environment that has some additional constraints and I was hoping to get
The first issue is related to spdk_mem_pool which used for the nvmeof
iovecs that are passed to the bdev layer
Is there a way to allow a bdev to allocate these? Or do I need to implement
my own spdk_mem_pool via the environment abstraction? I have a requirement
where the iovec memory needs to be accessible by other, non-SPDK processes
outside of the SPDK process.
The second question is related to the dynamic (spdk_) thread scheduling
that Ben presented. I would like to schedule threads dynamically to a
different core based on how loaded the cores are. In other words, if a core
is super busy, move the (spdk_) thread to another core.
Our threading environment is cooperative and the spdk_thread_poll function
would work great but it is unclear what do to
with _spdk_event_queue_run_batch() that processes reactor events.
This seems to be tied 1:1 to a reactor core. It is also unclear to me how I
would create our own reactor given that spdk_event_allocate/call API is in