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Message-Id: <20221208105947.2399894-26-niklas.cassel@wdc.com>
Date: Thu, 8 Dec 2022 11:59:41 +0100
From: Niklas Cassel <niklas.cassel@....com>
To: linux-kernel@...r.kernel.org
Cc: Hannes Reinecke <hare@...e.de>, linux-scsi@...r.kernel.org,
Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Subject: [PATCH 25/25] Documentation: sysfs-block-device: document command duration limits
From: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Document ABI/testing/sysfs-block-device the sysfs attributes present
under /sys/block/*/device/duration_limits for ATA and SCSI devices
supporting the command duration limits feature.
Signed-off-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
---
Documentation/ABI/testing/sysfs-block-device | 143 +++++++++++++++++++
1 file changed, 143 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-block-device b/Documentation/ABI/testing/sysfs-block-device
index 7ac7b19b2f72..44841f91c69b 100644
--- a/Documentation/ABI/testing/sysfs-block-device
+++ b/Documentation/ABI/testing/sysfs-block-device
@@ -95,3 +95,146 @@ Description:
This file does not exist if the HBA driver does not implement
support for the SATA NCQ priority feature, regardless of the
device support for this feature.
+
+
+What: /sys/block/*/device/duration_limits/enable
+Date: Dec, 2022
+KernelVersion: v6.3
+Contact: linux-scsi@...r.kernel.org
+Description:
+ (RW) For ATA and SCSI devices supporting the command duration
+ limits feature, write to the file to turn on or off the
+ feature. By default this feature is turned off. If the device
+ does not support the command duration limits feature, this
+ attribute does not exist (the directory
+ "/sys/block/*/device/duration_limits" does not exist).
+ Writing "1" to this file enables the use of command duration
+ limits for read and write commands in the kernel and turns on
+ the feature on the device. Writing "0" disables the feature.
+
+
+What: /sys/block/*/device/duration_limits/read/[1-7]/*
+Date: Dec, 2022
+KernelVersion: v6.3
+Contact: linux-scsi@...r.kernel.org
+Description:
+ (RO) For ATA and SCSI devices supporting the command duration
+ limits feature, this shows the set of 7 command duration limits
+ descriptors for read commands currently set on the device. For
+ each of the 7 descritors, the following read-only attributes
+ are present:
+
+ - duration_guideline: specifies the preferred length of time
+ in microseconds for the completion of a command.
+
+ - duration_guideline_policy: specifies the policy action
+ taken if the duration_guideline attribute specifies a
+ non-zero command duration guideline that the device is
+ unable to achieve for a command.
+
+ Possible values are:
+
+ - 0x0: The device will complete the command at the
+ earliest possible time consistent with the
+ specified command duration guideline.
+ - 0x1: If the specified command duration guideline has
+ not been achieved and the command duration
+ guideline policy field is not the seventh command
+ duration limits descriptor, then the device
+ continues processing that command using the
+ command duration limits descriptor that has
+ the next higher number.
+ - 0x2: The device will continue processing the command
+ as with no command duration limits descriptor
+ being used.
+ - 0xD: The device will complete the command and an IO
+ failure will be reported to the user with the ETIME
+ error code.
+ - 0xF: Same as 0xD.
+
+ - max_active_time: specifies an upper limit in microseconds
+ on the time that elapses from the time at which the device
+ initiates actions to access, transfer, or act upon the
+ specified data until the time the device returns status for
+ the command.
+
+ - max_active_time_policy: specifies the policy action taken
+ if the time used to process a command exceeds a non-zero
+ time specified by the max_active_time attribute.
+
+ Possible values are:
+
+ - 0x0: The device will complete the command at the
+ earliest possible time (i.e, do nothing based on
+ the max limit not being met).
+ - 0xD: The device will complete the command and an IO
+ failure will be reported to the user with the ETIME
+ error code.
+ - 0xE: Same as 0xD.
+ - 0xF: Same as 0xD.
+
+ - max_inactive_time: specifies an upper limit in microseconds
+ on the time that elapses from the time at which the device
+ receives the command until the time at which the device
+ initiates actions to access, transfer, or act upon the
+ specified data.
+
+ - max_inactive_time_policy: specifies the policy action taken
+ if a non-zero max_inactive_time limit is not met.
+
+ Possible values are:
+
+ - 0x0: The device will complete the command at the
+ earliest possible time (i.e, do nothing based on
+ the time limit not being met).
+ - 0xD: The device will complete the command and an IO
+ failure will be reported to the user with the ETIME
+ error code.
+ - 0xF: Same as 0xD.
+
+
+What: /sys/block/*/device/duration_limits/read/page
+Date: Dec, 2022
+KernelVersion: v6.3
+Contact: linux-scsi@...r.kernel.org
+Description:
+ (RO) For ATA and SCSI devices supporting the command duration
+ limits feature, this shows the name of the device VPD page
+ specifying the set of 7 command duration limits descriptors for
+ read commands. Possible values are "T2A" and "T2B".
+
+
+What: /sys/block/*/device/duration_limits/write/[1-7]/*
+Date: Dec, 2022
+KernelVersion: v6.3
+Contact: linux-scsi@...r.kernel.org
+Description:
+ (RO) For ATA and SCSI devices supporting the command duration
+ limits feature, this shows the set of 7 command duration limits
+ descriptors for write commands currently set on the device. For
+ each of the 7 descritors, the same set of read-only attributes
+ as for read commands is present.
+
+
+What: /sys/block/*/device/duration_limits/write/page
+Date: Dec, 2022
+KernelVersion: v6.3
+Contact: linux-scsi@...r.kernel.org
+Description:
+ (RO) For ATA and SCSI devices supporting the command duration
+ limits feature, this shows the name of the device VPD page
+ specifying the set of 7 command duration limits descriptors for
+ write commands. Possible values are "T2A" and "T2B".
+
+
+What: /sys/block/*/device/duration_limits/perf_vs_duration_guideline
+Date: Dec, 2022
+KernelVersion: v6.3
+Contact: linux-scsi@...r.kernel.org
+Description:
+ (RO) For ATA and SCSI devices supporting the command duration
+ limits feature, this specifies the maximum percentage increase
+ in average command completion times (reduction in IOPS) that
+ is allowed for the device to perform actions based on the
+ contents of the duration guideline field in every command
+ duration limit descriptor for both read and write commands.
--
2.38.1
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