What does Fedora Workstation 29 use as the default I/O scheduler?
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If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
Background information
The Fedora 29 release includes a Linux kernel from the 4.19 series. EDIT: The initial Fedora 29 release installs a kernel from the 4.18 series. However, a subsequent software update installs a 4.19 kernel.
Starting in version 4.19, the mainline kernel has CONFIG_SCSI_MQ_DEFAULT as default y. This means SCSI devices, including SATA, will use the new multi-queue (MQ) block layer.
(Linux treats SATA devices as being SCSI, using a translation like the SAT standard).
Block devices using the new MQ system use a new set of I/O schedulers. These include none, mq-deadline, bfq.
The mainline 4.19 kernel initializes the I/O scheduler to mq-deadline for all MQ devices. https://elixir.bootlin.com/linux/v4.19/source/block/elevator.c#L970
The default scheduler for the legacy SQ block layer is CFQ, which BFQ was based on. A suggestion has been made to automatically switch the I/O scheduler to BFQ, for block devices which use MQ but only have a single hardware queue. This suggestion was not accepted for 4.19.
=> The kernel's default I/O scheduler can vary, depending on the type of device: SCSI/SATA, MMC/eMMC, etc.
CFQ attempts to support some level of "fairness" and I/O priorities (ionice). It has various complexities. BFQ is even more complex; it supports ionice but also has heuristics to classify and prioritize some I/O automatically. deadline style scheduling is simpler; it does not support ionice at all.
=> Users with the Linux default kernel configuration, SATA devices, and no additional userspace policy (e.g. no udev rules), will be subject to a change in behaviour in 4.19. Where ionice used to work, it will no longer have any effect.
However Fedora includes specific kernel patches / configuration. Fedora also includes userspace policies such as default udev rules.
What does Fedora Workstation 29 use as the default I/O scheduler? If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
fedora linux-kernel io scsi
asked Nov 24 at 15:47
sourcejedi
22.1k43397
add a comment |
up vote
2
down vote
favorite
If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
Background information
The Fedora 29 release includes a Linux kernel from the 4.19 series. EDIT: The initial Fedora 29 release installs a kernel from the 4.18 series. However, a subsequent software update installs a 4.19 kernel.
Starting in version 4.19, the mainline kernel has CONFIG_SCSI_MQ_DEFAULT as default y. This means SCSI devices, including SATA, will use the new multi-queue (MQ) block layer.
(Linux treats SATA devices as being SCSI, using a translation like the SAT standard).
Block devices using the new MQ system use a new set of I/O schedulers. These include none, mq-deadline, bfq.
The mainline 4.19 kernel initializes the I/O scheduler to mq-deadline for all MQ devices. https://elixir.bootlin.com/linux/v4.19/source/block/elevator.c#L970
The default scheduler for the legacy SQ block layer is CFQ, which BFQ was based on. A suggestion has been made to automatically switch the I/O scheduler to BFQ, for block devices which use MQ but only have a single hardware queue. This suggestion was not accepted for 4.19.
=> The kernel's default I/O scheduler can vary, depending on the type of device: SCSI/SATA, MMC/eMMC, etc.
CFQ attempts to support some level of "fairness" and I/O priorities (ionice). It has various complexities. BFQ is even more complex; it supports ionice but also has heuristics to classify and prioritize some I/O automatically. deadline style scheduling is simpler; it does not support ionice at all.
=> Users with the Linux default kernel configuration, SATA devices, and no additional userspace policy (e.g. no udev rules), will be subject to a change in behaviour in 4.19. Where ionice used to work, it will no longer have any effect.
However Fedora includes specific kernel patches / configuration. Fedora also includes userspace policies such as default udev rules.
What does Fedora Workstation 29 use as the default I/O scheduler? If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
fedora linux-kernel io scsi
asked Nov 24 at 15:47
sourcejedi
22.1k43397
add a comment |
up vote
2
down vote
favorite
up vote
2
down vote
favorite
If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
Background information
The Fedora 29 release includes a Linux kernel from the 4.19 series. EDIT: The initial Fedora 29 release installs a kernel from the 4.18 series. However, a subsequent software update installs a 4.19 kernel.
Starting in version 4.19, the mainline kernel has CONFIG_SCSI_MQ_DEFAULT as default y. This means SCSI devices, including SATA, will use the new multi-queue (MQ) block layer.
(Linux treats SATA devices as being SCSI, using a translation like the SAT standard).
Block devices using the new MQ system use a new set of I/O schedulers. These include none, mq-deadline, bfq.
The mainline 4.19 kernel initializes the I/O scheduler to mq-deadline for all MQ devices. https://elixir.bootlin.com/linux/v4.19/source/block/elevator.c#L970
The default scheduler for the legacy SQ block layer is CFQ, which BFQ was based on. A suggestion has been made to automatically switch the I/O scheduler to BFQ, for block devices which use MQ but only have a single hardware queue. This suggestion was not accepted for 4.19.
=> The kernel's default I/O scheduler can vary, depending on the type of device: SCSI/SATA, MMC/eMMC, etc.
CFQ attempts to support some level of "fairness" and I/O priorities (ionice). It has various complexities. BFQ is even more complex; it supports ionice but also has heuristics to classify and prioritize some I/O automatically. deadline style scheduling is simpler; it does not support ionice at all.
=> Users with the Linux default kernel configuration, SATA devices, and no additional userspace policy (e.g. no udev rules), will be subject to a change in behaviour in 4.19. Where ionice used to work, it will no longer have any effect.
However Fedora includes specific kernel patches / configuration. Fedora also includes userspace policies such as default udev rules.
What does Fedora Workstation 29 use as the default I/O scheduler? If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
fedora linux-kernel io scsi
asked Nov 24 at 15:47
sourcejedi
22.1k43397
If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
Background information
The Fedora 29 release includes a Linux kernel from the 4.19 series. EDIT: The initial Fedora 29 release installs a kernel from the 4.18 series. However, a subsequent software update installs a 4.19 kernel.
Starting in version 4.19, the mainline kernel has CONFIG_SCSI_MQ_DEFAULT as default y. This means SCSI devices, including SATA, will use the new multi-queue (MQ) block layer.
(Linux treats SATA devices as being SCSI, using a translation like the SAT standard).
Block devices using the new MQ system use a new set of I/O schedulers. These include none, mq-deadline, bfq.
The mainline 4.19 kernel initializes the I/O scheduler to mq-deadline for all MQ devices. https://elixir.bootlin.com/linux/v4.19/source/block/elevator.c#L970
The default scheduler for the legacy SQ block layer is CFQ, which BFQ was based on. A suggestion has been made to automatically switch the I/O scheduler to BFQ, for block devices which use MQ but only have a single hardware queue. This suggestion was not accepted for 4.19.
=> The kernel's default I/O scheduler can vary, depending on the type of device: SCSI/SATA, MMC/eMMC, etc.
CFQ attempts to support some level of "fairness" and I/O priorities (ionice). It has various complexities. BFQ is even more complex; it supports ionice but also has heuristics to classify and prioritize some I/O automatically. deadline style scheduling is simpler; it does not support ionice at all.
=> Users with the Linux default kernel configuration, SATA devices, and no additional userspace policy (e.g. no udev rules), will be subject to a change in behaviour in 4.19. Where ionice used to work, it will no longer have any effect.
However Fedora includes specific kernel patches / configuration. Fedora also includes userspace policies such as default udev rules.
What does Fedora Workstation 29 use as the default I/O scheduler? If it depends on the exact type of block device, then what is the default I/O scheduler for each type of device?
fedora linux-kernel io scsi
fedora linux-kernel io scsi
asked Nov 24 at 15:47
sourcejedi
22.1k43397
asked Nov 24 at 15:47
sourcejedi
22.1k43397
edited Nov 24 at 16:22
asked Nov 24 at 15:47
sourcejedi
22.1k43397
asked Nov 24 at 15:47
sourcejedi
22.1k43397
asked Nov 24 at 15:47
sourcejedi
22.1k43397
22.1k43397
add a comment |
add a comment |
1 Answer
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Fedora 29 ships with the 4.18.16 kernel. It appears that CFQ is the default.
$ grep CONFIG_DEFAULT_IOSCHED= /boot/config-4.18.16-300.fc29.x86_64
CONFIG_DEFAULT_IOSCHED="cfq"
$ grep CONFIG_SCSI_MQ_DEFAULT /boot/config-4.18.16-300.fc29.x86_64
# CONFIG_SCSI_MQ_DEFAULT is not set
$ cat /sys/block/sda/queue/scheduler
noop deadline [cfq]
As of this writing (November 24, 2018), 4.19.3 is available as update for F29. But, the config options do not appear to have changed.
4.20.0 (RC1) is in the "Rawhide" devel tree. In that devel-tree kernel, CFQ is still the default, and CONFIG_SCSI_MQ_DEFAULT is still unset. The Fedora Kernel list at https://lists.fedoraproject.org/archives/list/kernel@lists.fedoraproject.org/ is the best place to discuss whether this should change.
answered Nov 24 at 16:07
mattdm
27.7k1172111
I don't think we have any udev rules to change this; there'd need to be a special circumstance for us to do it that way rather than with kernel config, I think.
– mattdm
Nov 24 at 16:10
Thanks again! I asked because I have a spinning HDD and was not really convinced about the upstream default of mq-deadline :-). I'm not hoping for Fedora to change - yet. Because I haven't tried BFQ yet. That might change soon :-).
– sourcejedi
Nov 24 at 16:26
add a comment |
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
accepted
Fedora 29 ships with the 4.18.16 kernel. It appears that CFQ is the default.
$ grep CONFIG_DEFAULT_IOSCHED= /boot/config-4.18.16-300.fc29.x86_64
CONFIG_DEFAULT_IOSCHED="cfq"
$ grep CONFIG_SCSI_MQ_DEFAULT /boot/config-4.18.16-300.fc29.x86_64
# CONFIG_SCSI_MQ_DEFAULT is not set
$ cat /sys/block/sda/queue/scheduler
noop deadline [cfq]
As of this writing (November 24, 2018), 4.19.3 is available as update for F29. But, the config options do not appear to have changed.
4.20.0 (RC1) is in the "Rawhide" devel tree. In that devel-tree kernel, CFQ is still the default, and CONFIG_SCSI_MQ_DEFAULT is still unset. The Fedora Kernel list at https://lists.fedoraproject.org/archives/list/kernel@lists.fedoraproject.org/ is the best place to discuss whether this should change.
answered Nov 24 at 16:07
mattdm
27.7k1172111
I don't think we have any udev rules to change this; there'd need to be a special circumstance for us to do it that way rather than with kernel config, I think.
– mattdm
Nov 24 at 16:10
Thanks again! I asked because I have a spinning HDD and was not really convinced about the upstream default of mq-deadline :-). I'm not hoping for Fedora to change - yet. Because I haven't tried BFQ yet. That might change soon :-).
– sourcejedi
Nov 24 at 16:26
add a comment |
up vote
3
down vote
accepted
Fedora 29 ships with the 4.18.16 kernel. It appears that CFQ is the default.
$ grep CONFIG_DEFAULT_IOSCHED= /boot/config-4.18.16-300.fc29.x86_64
CONFIG_DEFAULT_IOSCHED="cfq"
$ grep CONFIG_SCSI_MQ_DEFAULT /boot/config-4.18.16-300.fc29.x86_64
# CONFIG_SCSI_MQ_DEFAULT is not set
$ cat /sys/block/sda/queue/scheduler
noop deadline [cfq]
As of this writing (November 24, 2018), 4.19.3 is available as update for F29. But, the config options do not appear to have changed.
4.20.0 (RC1) is in the "Rawhide" devel tree. In that devel-tree kernel, CFQ is still the default, and CONFIG_SCSI_MQ_DEFAULT is still unset. The Fedora Kernel list at https://lists.fedoraproject.org/archives/list/kernel@lists.fedoraproject.org/ is the best place to discuss whether this should change.
answered Nov 24 at 16:07
mattdm
27.7k1172111
I don't think we have any udev rules to change this; there'd need to be a special circumstance for us to do it that way rather than with kernel config, I think.
– mattdm
Nov 24 at 16:10
Thanks again! I asked because I have a spinning HDD and was not really convinced about the upstream default of mq-deadline :-). I'm not hoping for Fedora to change - yet. Because I haven't tried BFQ yet. That might change soon :-).
– sourcejedi
Nov 24 at 16:26
add a comment |
up vote
3
down vote
accepted
up vote
3
down vote
accepted
Fedora 29 ships with the 4.18.16 kernel. It appears that CFQ is the default.
$ grep CONFIG_DEFAULT_IOSCHED= /boot/config-4.18.16-300.fc29.x86_64
CONFIG_DEFAULT_IOSCHED="cfq"
$ grep CONFIG_SCSI_MQ_DEFAULT /boot/config-4.18.16-300.fc29.x86_64
# CONFIG_SCSI_MQ_DEFAULT is not set
$ cat /sys/block/sda/queue/scheduler
noop deadline [cfq]
As of this writing (November 24, 2018), 4.19.3 is available as update for F29. But, the config options do not appear to have changed.
4.20.0 (RC1) is in the "Rawhide" devel tree. In that devel-tree kernel, CFQ is still the default, and CONFIG_SCSI_MQ_DEFAULT is still unset. The Fedora Kernel list at https://lists.fedoraproject.org/archives/list/kernel@lists.fedoraproject.org/ is the best place to discuss whether this should change.
answered Nov 24 at 16:07
mattdm
27.7k1172111
Fedora 29 ships with the 4.18.16 kernel. It appears that CFQ is the default.
$ grep CONFIG_DEFAULT_IOSCHED= /boot/config-4.18.16-300.fc29.x86_64
CONFIG_DEFAULT_IOSCHED="cfq"
$ grep CONFIG_SCSI_MQ_DEFAULT /boot/config-4.18.16-300.fc29.x86_64
# CONFIG_SCSI_MQ_DEFAULT is not set
$ cat /sys/block/sda/queue/scheduler
noop deadline [cfq]
As of this writing (November 24, 2018), 4.19.3 is available as update for F29. But, the config options do not appear to have changed.
4.20.0 (RC1) is in the "Rawhide" devel tree. In that devel-tree kernel, CFQ is still the default, and CONFIG_SCSI_MQ_DEFAULT is still unset. The Fedora Kernel list at https://lists.fedoraproject.org/archives/list/kernel@lists.fedoraproject.org/ is the best place to discuss whether this should change.
answered Nov 24 at 16:07
mattdm
27.7k1172111
edited Nov 24 at 16:22
answered Nov 24 at 16:07
mattdm
27.7k1172111
answered Nov 24 at 16:07
mattdm
27.7k1172111
answered Nov 24 at 16:07
mattdm
27.7k1172111
27.7k1172111
I don't think we have any udev rules to change this; there'd need to be a special circumstance for us to do it that way rather than with kernel config, I think.
– mattdm
Nov 24 at 16:10
Thanks again! I asked because I have a spinning HDD and was not really convinced about the upstream default of mq-deadline :-). I'm not hoping for Fedora to change - yet. Because I haven't tried BFQ yet. That might change soon :-).
– sourcejedi
Nov 24 at 16:26
add a comment |
I don't think we have any udev rules to change this; there'd need to be a special circumstance for us to do it that way rather than with kernel config, I think.
– mattdm
Nov 24 at 16:10
Thanks again! I asked because I have a spinning HDD and was not really convinced about the upstream default of mq-deadline :-). I'm not hoping for Fedora to change - yet. Because I haven't tried BFQ yet. That might change soon :-).
– sourcejedi
Nov 24 at 16:26
I don't think we have any udev rules to change this; there'd need to be a special circumstance for us to do it that way rather than with kernel config, I think.
– mattdm
Nov 24 at 16:10
I don't think we have any udev rules to change this; there'd need to be a special circumstance for us to do it that way rather than with kernel config, I think.
– mattdm
Nov 24 at 16:10
Thanks again! I asked because I have a spinning HDD and was not really convinced about the upstream default of mq-deadline :-). I'm not hoping for Fedora to change - yet. Because I haven't tried BFQ yet. That might change soon :-).
– sourcejedi
Nov 24 at 16:26
Thanks again! I asked because I have a spinning HDD and was not really convinced about the upstream default of mq-deadline :-). I'm not hoping for Fedora to change - yet. Because I haven't tried BFQ yet. That might change soon :-).
– sourcejedi
Nov 24 at 16:26
add a comment |
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