| Message ID | 1603326903-27052-1-git-send-email-michael.christie@oracle.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | vhost: fix scsi cmd handling and cgroup support | expand |
On Wed, Oct 21, 2020 at 07:34:46PM -0500, Mike Christie wrote: > In-Reply-To: > > The following patches were made over Michael's vhost branch here: > > https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git/log/?h=vhost > > They fix a couple issues with vhost-scsi when we hit the 256 cmd limit > that result in the guest getting IO errors, add LUN reset support so > devices are not offlined during transient errors, allow us to manage > vhost scsi IO with cgroups, and imrpove IOPs up to 2X. > > The following patches are a follow up to this post: > https://patchwork.kernel.org/project/target-devel/cover/1600712588-9514-1-git-send-email-michael.christie@oracle.com/ > which originally was fixing how vhost-scsi handled cmds so we would > not get IO errors when sending more than 256 cmds. > > In that patchset I needed to detect if a vq was in use and for this > patch: > https://patchwork.kernel.org/project/target-devel/patch/1600712588-9514-3-git-send-email-michael.christie@oracle.com/ > It was suggested to add support for VHOST_RING_ENABLE. While doing > that though I hit a couple problems: > > 1. The patches moved how vhost-scsi allocated cmds from per lio > session to per vhost vq. To support both VHOST_RING_ENABLE and > where userspace didn't support it, I would have to keep around the > old per session/device cmd allocator/completion and then also maintain > the new code. Or, I would still have to use this patch > patchwork.kernel.org/cover/11790763/ for the compat case so there > adding the new ioctl would not help much. > > 2. For vhost-scsi I also wanted to prevent where we allocate iovecs > for 128 vqs even though we normally use a couple. To do this, I needed > something similar to #1, but the problem is that the VHOST_RING_ENABLE > call would come too late. > > To try and balance #1 and #2, these patches just allow vhost-scsi > to setup a vq when userspace starts to config it. This allows the > driver to only fully setup (we still waste some memory to support older > setups but do not have to preallocate everything like before) what > is used plus I do not need to maintain 2 code paths. OK, so could we get a patchset with just bugfixes for this release please? And features should go into next one ... > V3: > - fix compile errors > - fix possible crash where cmd could be freed while adding it to > completion list > - fix issue where we added the worker thread to the blk cgroup but > the blk IO was submitted by a driver workqueue. > > V2: > - fix use before set cpu var errors > - drop vhost_vq_is_setup > - include patches to do a worker thread per scsi IO vq >
On 10/29/20 4:47 PM, Michael S. Tsirkin wrote: > On Wed, Oct 21, 2020 at 07:34:46PM -0500, Mike Christie wrote: >> In-Reply-To: >> >> The following patches were made over Michael's vhost branch here: >> >> https://urldefense.com/v3/__https://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git/log/?h=vhost__;!!GqivPVa7Brio!ORlQVwL5FxDLtNmvh5l9nLqhQJOO6UexX4vl-NrAhagQG9dAGFNFCPXoSNU8rW75g3OH$ >> >> They fix a couple issues with vhost-scsi when we hit the 256 cmd limit >> that result in the guest getting IO errors, add LUN reset support so >> devices are not offlined during transient errors, allow us to manage >> vhost scsi IO with cgroups, and imrpove IOPs up to 2X. >> >> The following patches are a follow up to this post: >> https://urldefense.com/v3/__https://patchwork.kernel.org/project/target-devel/cover/1600712588-9514-1-git-send-email-michael.christie@oracle.com/__;!!GqivPVa7Brio!ORlQVwL5FxDLtNmvh5l9nLqhQJOO6UexX4vl-NrAhagQG9dAGFNFCPXoSNU8rXJWM8fh$ >> which originally was fixing how vhost-scsi handled cmds so we would >> not get IO errors when sending more than 256 cmds. >> >> In that patchset I needed to detect if a vq was in use and for this >> patch: >> https://urldefense.com/v3/__https://patchwork.kernel.org/project/target-devel/patch/1600712588-9514-3-git-send-email-michael.christie@oracle.com/__;!!GqivPVa7Brio!ORlQVwL5FxDLtNmvh5l9nLqhQJOO6UexX4vl-NrAhagQG9dAGFNFCPXoSNU8rbRNqMbK$ >> It was suggested to add support for VHOST_RING_ENABLE. While doing >> that though I hit a couple problems: >> >> 1. The patches moved how vhost-scsi allocated cmds from per lio >> session to per vhost vq. To support both VHOST_RING_ENABLE and >> where userspace didn't support it, I would have to keep around the >> old per session/device cmd allocator/completion and then also maintain >> the new code. Or, I would still have to use this patch >> patchwork.kernel.org/cover/11790763/ for the compat case so there >> adding the new ioctl would not help much. >> >> 2. For vhost-scsi I also wanted to prevent where we allocate iovecs >> for 128 vqs even though we normally use a couple. To do this, I needed >> something similar to #1, but the problem is that the VHOST_RING_ENABLE >> call would come too late. >> >> To try and balance #1 and #2, these patches just allow vhost-scsi >> to setup a vq when userspace starts to config it. This allows the >> driver to only fully setup (we still waste some memory to support older >> setups but do not have to preallocate everything like before) what >> is used plus I do not need to maintain 2 code paths. > > > OK, so could we get a patchset with just bugfixes for this release > please? > And features should go into next one ... Yeah, that sounds good. Just to make sure I am on the same page as you and Jason about what patches are features vs fixes/cleanups. I'm thinking patches 1 - 11 are to resend in the fixes patchset? 0. Patches 1 - 2 are adding helpers I use later. 1. Patches 3 - 8 are related to fixing IO errors due to the VM sending virtqueue_size/cmd_per_lun commands but vhost-scsi having 256 hard coded. Patch: [PATCH 08/17] vhost scsi: alloc cmds per vq instead of session is what fixes the issue in vhost-scsi so we allocate enough resource to match what the VM is going to send us, but is built on patches 3 - 7 which allow vhost-scsi to know which vqs to allocate cmd resrouces for. [PATCH 03/17] vhost net: use goto error handling in open [PATCH 04/17] vhost: prep vhost_dev_init users to handle failures [PATCH 05/17] vhost: move vq iovec allocation to dev init time [PATCH 06/17] vhost: support delayed vq creation [PATCH 07/17] vhost scsi: support delayed IO vq creation 2. Patch 9 fixes a race where we signal userspace the cmd is done before we were done with it. We can then get IO errors if the VM sends a new IO before we free up the old cmd. 3. Patch 10 adds LUN reset support. Currently, if the real/backing device hits a temp issue, the VM's scsi/block layer cmd timer might fire and send a reset. We don't implement this, so we just fail. The VM's device goes offline and the app in the VM gets IO errors. 4. Patch 11 removes extra flush calls. Patches 12 - 17 are adding support for the thread per VQ which is a perf feature so resend them separately when we figure what is best.