We've seen cases where after creating a ZVOL, the ZVOL device node in
"/dev" isn't generated after 20 seconds of waiting, which is the point
at which our applications gives up on waiting and reports an error.
The workload when this occurs is to "refresh" 400+ ZVOLs roughly at the
same time, based on a policy set by the user. This refresh operation
will destroy the ZVOL, and re-create it based on a snapshot.
When this occurs, we see many hundreds of entries on the "z_zvol" taskq
(based on inspection of the /proc/spl/taskq-all file). Many of the
entries on the taskq end up in the "zvol_remove_minors_impl" function,
and I've measured the latency of that function:
Function = zvol_remove_minors_impl
msecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 1 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 1 | |
128 -> 255 : 45 |****************************************|
256 -> 511 : 5 |**** |
That data is from a 10 second sample, using the BCC "funclatency" tool.
As we can see, in this 10 second sample, most calls took 128ms at a
minimum. Thus, some basic math tells us that in any 20 second interval,
we could only process at most about 150 removals, which is much less
than the 400+ that'll occur based on the workload.
As a result of this, and since all ZVOL minor operations will go through
the single threaded "z_zvol" taskq, the latency for creating a single
ZVOL device can be unreasonably large due to other ZVOL activity on the
system. In our case, it's large enough to cause the application to
generate an error and fail the operation.
When profiling the "zvol_remove_minors_impl" function, I saw that most
of the time in the function was spent off-cpu, blocked in the function
"taskq_wait_outstanding". How this works, is "zvol_remove_minors_impl"
will dispatch calls to "zvol_free" using the "system_taskq", and then
the "taskq_wait_outstanding" function is used to wait for all of those
dispatched calls to occur before "zvol_remove_minors_impl" will return.
As far as I can tell, "zvol_remove_minors_impl" doesn't necessarily have
to wait for all calls to "zvol_free" to occur before it returns. Thus,
this change removes the call to "taskq_wait_oustanding", so that calls
to "zvol_free" don't affect the latency of "zvol_remove_minors_impl".
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Gallagher <john.gallagher@delphix.com>
Signed-off-by: Prakash Surya <prakash.surya@delphix.com>
Closes#9380
Refactor the zfs ioctls in to platform dependent and independent bits.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Sean Eric Fagan <sef@ixsystems.com>
Signed-off-by: Matthew Macy <mmacy@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes#9301
Originally the zfs_vdev_elevator module option was added as a
convenience so the requested elevator would be automatically set
on the underlying block devices. At the time this was simple
because the kernel provided an API function which did exactly this.
This API was then removed in the Linux 4.12 kernel which prompted
us to add compatibly code to set the elevator via a usermodehelper.
While well intentioned this introduced a bug which could cause a
system hang, that issue was subsequently fixed by commit 2a0d4188.
In order to avoid future bugs in this area, and to simplify the code,
this functionality is being deprecated. A console warning has been
added to notify any existing consumers and the documentation updated
accordingly. This option will remain for the lifetime of the 0.8.x
series for compatibility but if planned to be phased out of master.
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: loli10K <ezomori.nozomu@gmail.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #8664Closes#9317
Refactor the zvol in to platform dependent and independent bits.
Reviewed-by: Allan Jude <allanjude@freebsd.org>
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes#9295
Originally the zfs_vdev_elevator module option was added as a
convenience so the requested elevator would be automatically set
on the underlying block devices. At the time this was simple
because the kernel provided an API function which did exactly this.
This API was then removed in the Linux 4.12 kernel which prompted
us to add compatibly code to set the elevator via a usermodehelper.
Unfortunately changing the evelator via usermodehelper requires reading
some userland binaries, most notably modprobe(8) or sh(1), from a zfs
dataset on systems with root-on-zfs. This can deadlock the system if
used during the following call path because it may need, if the data
is not already cached in the ARC, reading directly from disk while
holding the spa config lock as a writer:
zfs_ioc_pool_scan()
-> spa_scan()
-> spa_scan()
-> vdev_reopen()
-> vdev_elevator_switch()
-> call_usermodehelper()
While the usermodehelper waits sh(1), modprobe(8) is blocked in the
ZIO pipeline trying to read from disk:
INFO: task modprobe:2650 blocked for more than 10 seconds.
Tainted: P OE 5.2.14
modprobe D 0 2650 206 0x00000000
Call Trace:
? __schedule+0x244/0x5f0
schedule+0x2f/0xa0
cv_wait_common+0x156/0x290 [spl]
? do_wait_intr_irq+0xb0/0xb0
spa_config_enter+0x13b/0x1e0 [zfs]
zio_vdev_io_start+0x51d/0x590 [zfs]
? tsd_get_by_thread+0x3b/0x80 [spl]
zio_nowait+0x142/0x2f0 [zfs]
arc_read+0xb2d/0x19d0 [zfs]
...
zpl_iter_read+0xfa/0x170 [zfs]
new_sync_read+0x124/0x1b0
vfs_read+0x91/0x140
ksys_read+0x59/0xd0
do_syscall_64+0x4f/0x130
entry_SYSCALL_64_after_hwframe+0x44/0xa9
This commit changes how we use the usermodehelper functionality from
synchronous (UMH_WAIT_PROC) to asynchronous (UMH_NO_WAIT) which prevents
scrubs, and other vdev_elevator_switch() consumers, from triggering the
aforementioned issue.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Issue #8664Closes#9321
1. Fix issue: Kernel BUG with QAT during decompression #9276.
Now it is uninterruptible for a specific given QAT request,
but Ctrl-C interrupt still works in user-space process.
2. Copy the digest result to the buffer only when doing encryption,
and vise-versa for decryption.
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chengfei Zhu <chengfeix.zhu@intel.com>
Closes#9276Closes#9303
objnode is OS agnostic and used only by dmu_redact.c.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes#9315
Move Linux specific tracing headers and source to platform directories
and update the build system.
Reviewed-by: Allan Jude <allanjude@freebsd.org>
Reviewed-by: Ryan Moeller <ryan@ixsystems.com>
Reviewed by: Brad Lewis <brad.lewis@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Closes#9290
When adding the SIMD compatibility code in e5db313 the decryption of a
dataset wrapping key was left in a user thread context. This was done
intentionally since it's a relatively infrequent operation. However,
this also meant that the encryption context templates were initialized
using the generic operations. Therefore, subsequent encryption and
decryption operations would use the generic implementation even when
executed by an I/O pipeline thread.
Resolve the issue by initializing the context templates in an I/O
pipeline thread. And by updating zio_do_crypt_uio() to dispatch any
encryption operations to a pipeline thread when called from the user
context. For example, when performing a read from the ARC.
Tested-by: Attila Fülöp <attila@fueloep.org>
Reviewed-by: Tom Caputi <tcaputi@datto.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes#9215Closes#9296
Move platform specific Linux source under module/os/linux/
and update the build system accordingly. Additional code
restructuring will follow to make the common code fully
portable.
Reviewed-by: Jorgen Lundman <lundman@lundman.net>
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matthew Macy <mmacy@FreeBSD.org>
Closes#9206
