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author | Avri Altman <avri.altman@wdc.com> | 2021-07-12 12:50:39 +0300 |
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committer | Martin K. Petersen <martin.petersen@oracle.com> | 2021-08-01 16:05:15 -0400 |
commit | f95f59a2bb60f917faf516f2f0a679dc4e58f490 (patch) | |
tree | f060195f7ac69eb856b459a634cebb9f9dbd0b1b /Documentation | |
parent | 5dea655a09e6395f461ba0f9d38914c2c0d772e4 (diff) | |
download | linux-f95f59a2bb60f917faf516f2f0a679dc4e58f490.tar.bz2 |
scsi: ufs: ufshpb: Make host mode parameters configurable
Elaborate some more on the host control mode logic parameters, explaining
what they do and how to configure them.
Link: https://lore.kernel.org/r/20210712095039.8093-13-avri.altman@wdc.com
Reviewed-by: Daejun Park <daejun7.park@samsung.com>
Signed-off-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/ABI/testing/sysfs-driver-ufs | 76 |
1 files changed, 75 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/sysfs-driver-ufs b/Documentation/ABI/testing/sysfs-driver-ufs index 929460738651..ec3a7149ced5 100644 --- a/Documentation/ABI/testing/sysfs-driver-ufs +++ b/Documentation/ABI/testing/sysfs-driver-ufs @@ -1449,7 +1449,7 @@ Description: This entry shows the maximum HPB data size for using a single HPB The file is read only. -What: /sys/bus/platform/drivers/ufshcd/*/flags/wb_enable +What: /sys/bus/platform/drivers/ufshcd/*/flags/hpb_enable Date: June 2021 Contact: Daejun Park <daejun7.park@samsung.com> Description: This entry shows the status of HPB. @@ -1460,3 +1460,77 @@ Description: This entry shows the status of HPB. == ============================ The file is read only. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/activation_thld +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: In host control mode, reads are the major source of activation + trials. Once this threshold hs met, the region is added to the + "to-be-activated" list. Since we reset the read counter upon + write, this include sending a rb command updating the region + ppn as well. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/normalization_factor +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: In host control mode, we think of the regions as "buckets". + Those buckets are being filled with reads, and emptied on write. + We use entries_per_srgn - the amount of blocks in a subregion as + our bucket size. This applies because HPB1.0 only handles + single-block reads. Once the bucket size is crossed, we trigger + a normalization work - not only to avoid overflow, but mainly + because we want to keep those counters normalized, as we are + using those reads as a comparative score, to make various decisions. + The normalization is dividing (shift right) the read counter by + the normalization_factor. If during consecutive normalizations + an active region has exhausted its reads - inactivate it. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/eviction_thld_enter +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: Region deactivation is often due to the fact that eviction took + place: A region becomes active at the expense of another. This is + happening when the max-active-regions limit has been crossed. + In host mode, eviction is considered an extreme measure. We + want to verify that the entering region has enough reads, and + the exiting region has much fewer reads. eviction_thld_enter is + the min reads that a region must have in order to be considered + a candidate for evicting another region. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/eviction_thld_exit +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: Same as above for the exiting region. A region is considered to + be a candidate for eviction only if it has fewer reads than + eviction_thld_exit. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/read_timeout_ms +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: In order not to hang on to "cold" regions, we inactivate + a region that has no READ access for a predefined amount of + time - read_timeout_ms. If read_timeout_ms has expired, and the + region is dirty, it is less likely that we can make any use of + HPB reading it so we inactivate it. Still, deactivation has + its overhead, and we may still benefit from HPB reading this + region if it is clean - see read_timeout_expiries. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/read_timeout_expiries +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: If the region read timeout has expired, but the region is clean, + just re-wind its timer for another spin. Do that as long as it + is clean and did not exhaust its read_timeout_expiries threshold. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/timeout_polling_interval_ms +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: The frequency with which the delayed worker that checks the + read_timeouts is awakened. + +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/inflight_map_req +Date: February 2021 +Contact: Avri Altman <avri.altman@wdc.com> +Description: In host control mode the host is the originator of map requests. + To avoid flooding the device with map requests, use a simple throttling + mechanism that limits the number of inflight map requests. |