To complete a command several drivers just drop their reference and add
it to list to be processed by a driver specific thread. So there's no
need to go from backend context to the LIO thread then to the driver's
thread. When avoiding the LIO thread, IOPS can increase from 20-30% for
workloads like:
fio --filename=/dev/sdb --direct=1 --rw=randrw --bs=8K \
--ioengine=libaio --iodepth=128 --numjobs=$jobs
where increasing jobs increases the performance improvement (this is
using NVMe drives with LIO's submit_type=1 to directly submit).
Add the infrastructure so drivers and userspace can control how to
complete a command like is done for the submission path. In this commit
there is no behavior change and we continue to defer to the LIO
workqueue thread. In the subsequent commits we will allow drivers to
report what they support and allow userspace to control the behavior.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://patch.msgid.link/20260222232946.7637-2-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Add emulation for REPORT IDENTIFYING INFORMATION command using the
configfs file 'pd_text_id_info' in target core module. The configfs file
is created in /sys/kernel/config/target/core/<backend type>/
<backing_store_name>/wwn/.
An emulation function, spc_emulate_report_id_info(), is defined to
return the identification string based on the contents of
'pd_text_id_info'.
The details of the REPORT IDENTIFYING INFORMATION command is defined in
section 6.32 of SPC4.
[mkp: checkpatch tweaks]
Signed-off-by: Gulam Mohamed <gulam.mohamed@oracle.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://patch.msgid.link/20251201110716.227588-1-gulam.mohamed@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
The atomic use in the main I/O path is causing perf issues when using
higher performance backend devices and multiple queues (more than
10 when using vhost-scsi) like with this fio workload:
[global]
bs=4K
iodepth=128
direct=1
ioengine=libaio
group_reporting
time_based
runtime=120
name=standard-iops
rw=randread
numjobs=16
cpus_allowed=0-15
To fix this issue, move the LUN stats to per CPU.
Note: I forgot to include this patch with the delayed/ordered per CPU
tracking and per device/device entry per CPU stats. With this patch you
get the full 33% improvements when using fast backends, multiple queues
and multiple IO submiters.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Dmitry Bogdanov <d.bogdanov@yadro.com>
Link: https://patch.msgid.link/20250917221338.14813-4-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
asm/unaligned.h is always an include of asm-generic/unaligned.h;
might as well move that thing to linux/unaligned.h and include
that - there's nothing arch-specific in that header.
auto-generated by the following:
for i in `git grep -l -w asm/unaligned.h`; do
sed -i -e "s/asm\/unaligned.h/linux\/unaligned.h/" $i
done
for i in `git grep -l -w asm-generic/unaligned.h`; do
sed -i -e "s/asm-generic\/unaligned.h/linux\/unaligned.h/" $i
done
git mv include/asm-generic/unaligned.h include/linux/unaligned.h
git mv tools/include/asm-generic/unaligned.h tools/include/linux/unaligned.h
sed -i -e "/unaligned.h/d" include/asm-generic/Kbuild
sed -i -e "s/__ASM_GENERIC/__LINUX/" include/linux/unaligned.h tools/include/linux/unaligned.h
This allows userspace to request the fabric drivers do direct submissions
if they support it. With the new device file, submit_type, users can
write 0 - 2 to control how commands are submitted to the backend:
0 - TARGET_FABRIC_DEFAULT_SUBMIT - LIO will use the fabric's default
submission type. This is the default for compat.
1 - TARGET_DIRECT_SUBMIT - LIO will submit the cmd to the backend from the
calling context if the fabric the cmd was received on supports it,
else it will use the fabric's default type.
2 - TARGET_QUEUE_SUBMIT - LIO will queue the cmd to the LIO submission
workqueue which will pass it to the backend.
When using an NVMe drive and vhost-scsi with direct submission we see
around a 20% improvement in 4K I/Os:
fio jobs 1 2 4 8 10
--------------------------------------------------
defer 94K 190K 394K 770K 890K
direct 128K 252K 488K 950K -
And when using the queueing mode, we now no longer see issues like where
the iSCSI tx thread is blocked in the block layer waiting on a tag so it
can't respond to a nop or perform I/Os for other LUs.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230928020907.5730-6-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Move core_alua_check_nonop_delay() to transport_handle_cdb_direct() so the
iSCSI target driver doesn't have to call as many core functions
directly. We will eventually merge transport_handle_cdb_direct and
target_submit so iSCSI and the other drivers call a common function.
It will also be helpful as preparation for future changes which allow the
iSCSI target to defer command submission to the LIO submission workqueue,
because we will have a common submission function for that which will be
based on transport_handle_cdb_direct()/target_submit().
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230928020907.5730-3-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
In some cases, like with multiple LUN targets or where the target has to
respond to transport level requests from the receiving context it can be
better to defer cmd submission to a helper thread. If the backend driver
blocks on something like request/tag allocation it can block the entire
target submission path and other LUs and transport IO on that session.
In other cases like single LUN targets with storage that can support all
the commands that the target can queue, then it's best to submit the cmd
to the backend from the target's cmd receiving context.
Subsequent commits will allow the user to config what they prefer, but
drivers like loop can't directly submit because they can be called from a
context that can't sleep. And, drivers like vhost-scsi can support direct
submission, but need to keep their default behavior of deferring execution
to avoid possible regressions where the backend can block.
Make the drivers tell LIO core if they support direct submissions and their
current default, so we can prevent users from misconfiguring the system and
initialize devices correctly.
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Link: https://lore.kernel.org/r/20230928020907.5730-2-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Pull SCSI updates from James Bottomley:
"Updates to the usual drivers (ufs, pm80xx, libata-scsi, smartpqi,
lpfc, qla2xxx).
We have a couple of major core changes impacting other systems:
- Command Duration Limits, which spills into block and ATA
- block level Persistent Reservation Operations, which touches block,
nvme, target and dm
Both of these are added with merge commits containing a cover letter
explaining what's going on"
* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (187 commits)
scsi: core: Improve warning message in scsi_device_block()
scsi: core: Replace scsi_target_block() with scsi_block_targets()
scsi: core: Don't wait for quiesce in scsi_device_block()
scsi: core: Don't wait for quiesce in scsi_stop_queue()
scsi: core: Merge scsi_internal_device_block() and device_block()
scsi: sg: Increase number of devices
scsi: bsg: Increase number of devices
scsi: qla2xxx: Remove unused nvme_ls_waitq wait queue
scsi: ufs: ufs-pci: Add support for Intel Arrow Lake
scsi: sd: sd_zbc: Use PAGE_SECTORS_SHIFT
scsi: ufs: wb: Add explicit flush_threshold sysfs attribute
scsi: ufs: ufs-qcom: Switch to the new ICE API
scsi: ufs: dt-bindings: qcom: Add ICE phandle
scsi: ufs: ufs-mediatek: Set UFSHCD_QUIRK_MCQ_BROKEN_RTC quirk
scsi: ufs: ufs-mediatek: Set UFSHCD_QUIRK_MCQ_BROKEN_INTR quirk
scsi: ufs: core: Add host quirk UFSHCD_QUIRK_MCQ_BROKEN_RTC
scsi: ufs: core: Add host quirk UFSHCD_QUIRK_MCQ_BROKEN_INTR
scsi: ufs: core: Remove dedicated hwq for dev command
scsi: ufs: core: mcq: Fix the incorrect OCS value for the device command
scsi: ufs: dt-bindings: samsung,exynos: Drop unneeded quotes
...
Mike Christie <michael.christie@oracle.com> says:
The patches in this thread allow us to use the block pr_ops with LIO's
target_core_iblock module to support cluster applications in VMs. They
were built over Linus's tree. They also apply over linux-next and
Martin's tree and Jens's trees.
Currently, to use windows clustering or linux clustering (pacemaker +
cluster labs scsi fence agents) in VMs with LIO and vhost-scsi, you
have to use tcmu or pscsi or use a cluster aware FS/framework for the
LIO pr file. Setting up a cluster FS/framework is pain and waste when
your real backend device is already a distributed device, and pscsi
and tcmu are nice for specific use cases, but iblock gives you the
best performance and allows you to use stacked devices like
dm-multipath. So these patches allow iblock to work like pscsi/tcmu
where they can pass a PR command to the backend module. And then
iblock will use the pr_ops to pass the PR command to the real devices
similar to what we do for unmap today.
The patches are separated in the following groups:
Patch 1 - 2:
- Add block layer callouts for reading reservations and rename reservation
error code.
Patch 3 - 5:
- SCSI support for new callouts.
Patch 6:
- DM support for new callouts.
Patch 7 - 13:
- NVMe support for new callouts.
Patch 14 - 18:
- LIO support for new callouts.
This patchset has been tested with the libiscsi PGR ops and with
window's failover cluster verification test. Note that for scsi
backend devices we need this patchset:
https://lore.kernel.org/linux-scsi/20230123221046.125483-1-michael.christie@oracle.com/T/#m4834a643ffb5bac2529d65d40906d3cfbdd9b1b7
to handle UAs. To reduce the size of this patchset that's being done
separately to make reviewing easier. And to make merging easier this
patchset and the one above do not have any conflicts so can be merged
in different trees.
Link: https://lore.kernel.org/r/20230407200551.12660-1-michael.christie@oracle.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
