On Thu, Feb 18, 2021 at 03:19:32PM +0200, Avri Altman wrote: > We can make use of this commit, to elaborate some more of the host > control mode logic, explaining what role play each and every variable. > > While at it, allow those parameters to be configurable. > > Signed-off-by: Avri Altman <avri.altman@xxxxxxx> > --- > Documentation/ABI/testing/sysfs-driver-ufs | 68 ++++++ > drivers/scsi/ufs/ufshpb.c | 254 +++++++++++++++++++-- > drivers/scsi/ufs/ufshpb.h | 18 ++ > 3 files changed, 326 insertions(+), 14 deletions(-) > > diff --git a/Documentation/ABI/testing/sysfs-driver-ufs b/Documentation/ABI/testing/sysfs-driver-ufs > index 0017eaf89cbe..1d72201c4953 100644 > --- a/Documentation/ABI/testing/sysfs-driver-ufs > +++ b/Documentation/ABI/testing/sysfs-driver-ufs > @@ -1322,3 +1322,71 @@ Description: This entry shows the maximum HPB data size for using single 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@xxxxxxx> > +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@xxxxxxx> > +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 concern a > + 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 exhaust its reads - inactivate it. > + > +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/eviction_thld_enter > +Date: February 2021 > +Contact: Avri Altman <avri.altman@xxxxxxx> > +Description: Region deactivation is often due to the fact that eviction took > + place: a region become active on the expense of another. This is > + happening when the max-active-regions limit has 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 less reads. eviction_thld_enter is > + the min reads that a region must have in order to be considered > + as a candidate to evict other region. > + > +What: /sys/class/scsi_device/*/device/hpb_param_sysfs/eviction_thld_exit > +Date: February 2021 > +Contact: Avri Altman <avri.altman@xxxxxxx> > +Description: same as above for the exiting region. A region is consider to > + be a candidate to be evicted, only if it has less 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@xxxxxxx> > +Description: In order not to hang on to “cold” regions, we shall 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@xxxxxxx> > +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@xxxxxxx> > +Description: the frequency in which the delayed worker that checks the > + read_timeouts is awaken. > +>>>>>>> ef6bf08e666d... scsi: ufshpb: Make host mode parameters configurable Did you mean for this last line to be here?
