What: /sys/
class/bdi/<bdi>/
Date: January 2008
Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
Provide a place in sysfs
for the backing_dev_info object.
This allows
setting
and retrieving various BDI specific variables.
The <bdi> identifier can be either of the following:
MAJOR:MINOR
Device number
for block devices,
or value of st_dev on
non-block filesystems which provide their own BDI, such as NFS
and FUSE.
MAJOR:MINOR-fuseblk
Value of st_dev on fuseblk filesystems.
default
The
default backing dev, used
for non-block device backed
filesystems which
do not provide their own BDI.
What: /sys/
class/bdi/<bdi>/read_ahead_kb
Date: January 2008
Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
Size of the read-ahead window in kilobytes
(read-write)
What: /sys/
class/bdi/<bdi>/min_ratio
Date: January 2008
Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
Under normal circumstances each device is given a part of the
total write-back cache that relates to its current average
writeout speed in relation to the other devices.
The
'min_ratio' parameter allows assigning a minimum
percentage of the write-back cache to a particular device.
For example,
this is useful
for providing a minimum QoS.
(read-write)
What: /sys/
class/bdi/<bdi>/min_ratio_fine
Date: November 2022
Contact: Stefan Roesch <shr@devkernel.io>
Description:
Under normal circumstances each device is given a part of the
total write-back cache that relates to its current average
writeout speed in relation to the other devices.
The
'min_ratio_fine' parameter allows assigning a minimum reserve
of the write-back cache to a particular device. The value is
expressed as part of 1 million.
For example,
this is useful
for
providing a minimum QoS.
(read-write)
What: /sys/
class/bdi/<bdi>/max_ratio
Date: January 2008
Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
Allows limiting a particular device to use
not more than the
given percentage of the write-back cache.
This is useful in
situations where we want to avoid one device taking all
or
most of the write-back cache.
For example in
case of an NFS
mount that is prone to get stuck,
or a FUSE mount which cannot
be trusted to play fair.
(read-write)
What: /sys/
class/bdi/<bdi>/max_ratio_fine
Date: November 2022
Contact: Stefan Roesch <shr@devkernel.io>
Description:
Allows limiting a particular device to use
not more than the
given value of the write-back cache. The value is given as part
of 1 million.
This is useful in situations where we want to avoid
one device taking all
or most of the write-back cache.
For example
in
case of an NFS mount that is prone to get stuck,
or a FUSE mount
which cannot be trusted to play fair.
(read-write)
What: /sys/
class/bdi/<bdi>/min_bytes
Date: October 2022
Contact: Stefan Roesch <shr@devkernel.io>
Description:
Under normal circumstances each device is given a part of the
total write-back cache that relates to its current average
writeout speed in relation to the other devices.
The
'min_bytes' parameter allows assigning a minimum
percentage of the write-back cache to a particular device
expressed in bytes.
For example,
this is useful
for providing a minimum QoS.
(read-write)
What: /sys/
class/bdi/<bdi>/max_bytes
Date: October 2022
Contact: Stefan Roesch <shr@devkernel.io>
Description:
Allows limiting a particular device to use
not more than the
given
'max_bytes' of the write-back cache.
This is useful in
situations where we want to avoid one device taking all
or
most of the write-back cache.
For example in
case of an NFS
mount that is prone to get stuck, a FUSE mount which cannot be
trusted to play fair,
or a nbd device.
(read-write)
What: /sys/
class/bdi/<bdi>/strict_limit
Date: October 2022
Contact: Stefan Roesch <shr@devkernel.io>
Description:
Forces per-BDI checks
for the share of given device in the write-back
cache even before the global background dirty limit is reached.
This
is useful in situations where the global limit is much higher than
affordable
for given relatively slow (
or untrusted) device. Turning
strictlimit on has no visible effect
if max_ratio is equal to 100%.
(read-write)
What: /sys/
class/bdi/<bdi>/stable_pages_required
Date: January 2008
Contact: Peter Zijlstra <a.p.zijlstra@chello.nl>
Description:
If set, the backing device requires that all pages comprising a write
request must
not be changed until writeout is complete.
(read-only)
