Hi

Il giorno 18 ago 2022, alle ore 17:40, Tyler Erickson [off-list ref] ha scritto:

The libata layer is reporting correctly after the changes I submitted.

The drive reports the actuator ranges as a starting LBA and a count of LBAs for the range.
If the code reading the reported values simply does startingLBA + range, this is an incorrect ending LBA for that actuator. This is because LBAs are zero indexed and this simple addition is not taking that into account.
The proper way to get the endingLBA is startingLBA + range - 1 to get the last LBA value for where to issue a final IO read/write to account for LBA values starting at zero rather than one.

Here is an example from the output in SeaChest/openSeaChest:
====Concurrent Positioning Ranges====

Range#     #Elements            Lowest LBA          # of LBAs      
  0            1                                               0           17578328064
  1            1                         17578328064           17578328064

If using the incorrect formula to get the final LBA for actuator 0, you would get 17578328064, but this is the starting LBA reported by the drive for actuator 1.
So to be consistent for all ranges, the final LBA for a given actuator should be calculated as starting LBA + range - 1.

Ok

I had reached out to Seagate's T10 and T13 representatives for clarification and verification and this is most likely what is causing the error is a missing - 1 somewhere after getting the information reported by the device. They agreed that the reporting from the drive and the SCSI to ATA translation is correct.

I'm not sure where this is being read and calculated, but it is not an error in the low-level libata or sd level of the kernel. It may be in bfq, or it may be in some other place after the sd layer.

This apparent mistake is in the macro bio_end_sector (defined in
include/linux/bio.h), which seems to be translated as sector+size.
Jens, can you shed a light on this point?

Thanks,
Paolo

I know there were some additions to read this and report it up the stack, but I did not think those were wrong as they seemed to pass the drive reported information up the stack.

Tyler Erickson
Seagate Technology


Seagate Internal

-----Original Message-----
From: Rory Chen <redacted> 
Sent: Wednesday, August 10, 2022 6:59 AM
To: Paolo Valente <redacted>
Cc: Arie van der Hoeven <redacted>; Muhammad Ahmad <redacted>; linux-block@vger.kernel.org; linux-kernel@vger.kernel.org; Jan Kara <jack@suse.cz>; andrea.righi@canonical.com; glen.valante@linaro.org; axboe@kernel.dk; Tyler Erickson <redacted>; Michael English <redacted>; Andrew Ring <redacted>; Varun Boddu <redacted>
Subject: Re: [PATCH 0/8] block, bfq: extend bfq to support multi-actuator drives

The block trace shows the start sector is 35156656120 and transfer length is 8 sectors, which is within the max LBA 35156656127 of drive. And this IO is completed successfully from the slice of parsed block trace though reporting the warning message.
8,64   7       13     0.039401337 19176  Q  RA 35156656120 + 8 [systemd-udevd]
 8,64   7       15     0.039403946 19176  P   N [systemd-udevd]
 8,64   7       16     0.039405132 19176  I  RA 35156656120 + 8 [systemd-udevd]
 8,64   7       18     0.039411554 19176  D  RA 35156656120 + 8 [systemd-udevd]
 8,64   0       40     0.039479055     0  C  RA 35156656120 + 8 [0]

It may need to know where calculate "bio_end_sector" value as 35156656128. I have patched libata and sd driver for Dual Actuator.



From: Paolo Valente <redacted>
Sent: Wednesday, August 10, 2022 6:22 PM
To: Rory Chen <redacted>
Cc: Arie van der Hoeven <redacted>; Muhammad Ahmad <redacted>; linux-block@vger.kernel.org <redacted>; linux-kernel@vger.kernel.org <redacted>; Jan Kara <jack@suse.cz>; andrea.righi@canonical.com <redacted>; glen.valante@linaro.org <redacted>; axboe@kernel.dk <axboe@kernel.dk>; Tyler Erickson <redacted>; Michael English <redacted>; Andrew Ring <redacted>; Varun Boddu <redacted>
Subject: Re: [PATCH 0/8] block, bfq: extend bfq to support multi-actuator drives


This message has originated from an External Source. Please use proper judgment and caution when opening attachments, clicking links, or responding to this email.

quoted

Il giorno 9 ago 2022, alle ore 05:47, Rory Chen [off-list ref] ha scritto:

Resend the mail as plain text because previous mail with rich text 
makes some mess and forget to add others at Seagate who worked on 
validating the patch as well(Muhammad, Michael, Andrew, Varun,Tyler)

Hi Paolo,

Hi

quoted

I am from Seagate China and face a problem when I'm evaluating the bfq patches. Could you please check?
Thanks

Issue statement
When running performance test on bfq patch, I observed warning message "bfq_actuator_index: bio sector out of ranges: end=35156656128" and OS hung suddenly after some hours.
The warning message is reported from function bfq_actuator_index which determines IO request is in which index of actuators.  The bio_end_sector is 35156656128 but the max LBA for the drive is 35156656127 so it's beyond the LBA range.

Yep, this sanity check fails if the end sector of a new IO does not belong to any sector range.

quoted

I captured the block trace and didn't found request LBA 35156656128 instead only found max request LBA 35156656127.

Maybe in the trace you see only start sectors?  The failed check si performed on end sectors instead.

At any rate, there seems to be an off-by-one error in the value(s) stored in the sector field(s) of the blk_independent_access_range data structure.

I guess we may need some help/feedback from people competent on this stuff.

quoted

I'm not sure if this warning message is related to later OS hung.

Not easy to say.  At any rate, we can try with a development version of bfq.  It can help us detect the possible cause of this hang.  But let's see where we get with this sector error first.

Thank you for testing this extended version of bfq, Paolo

quoted

Problem environment
Kernel base is 5.18.9
Test HDD drive is Seagate ST18000NM0092 dual actuator SATA.
Actuator LBA mapping by reading VPD B9 Concurrent positioning ranges 
VPD page:
LBA range number:0
number of storage elements:1
starting LBA:0x0
number of LBAs:0x417c00000 [17578328064] LBA range number:1 number of 
storage elements:1 starting LBA:0x417c00000 number of LBAs:0x417c00000 
[17578328064]





From: Paolo Valente <redacted>
Sent: Thursday, June 23, 2022 8:53 AM
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org <redacted>; 
linux-kernel@vger.kernel.org [off-list ref]; 
jack@suse.cz [off-list ref]; andrea.righi@canonical.com 
[off-list ref]; glen.valante@linaro.org 
[off-list ref]; Arie van der Hoeven 
[off-list ref]; Paolo Valente 
[off-list ref]
Subject: [PATCH 0/8] block, bfq: extend bfq to support multi-actuator 
drives


This message has originated from an External Source. Please use proper judgment and caution when opening attachments, clicking links, or responding to this email.


Hi,
this patch series extends BFQ so as to optimize I/O dispatch to 
multi-actuator drives. In particular, this extension addresses the 
following issue. Multi-actuator drives appear as a single device to 
the I/O subsystem [1].  Yet they address commands to different 
actuators internally, as a function of Logical Block Addressing 
(LBAs). A given sector is reachable by only one of the actuators. For 
example, Seagate's Serial Advanced Technology Attachment (SATA) 
version contains two actuators and maps the lower half of the SATA LBA 
space to the lower actuator and the upper half to the upper actuator.

Evidently, to fully utilize actuators, no actuator must be left idle 
or underutilized while there is pending I/O for it. To reach this 
goal, the block layer must somehow control the load of each actuator 
individually. This series enriches BFQ with such a per-actuator 
control, as a first step. Then it also adds a simple mechanism for 
guaranteeing that actuators with pending I/O are never left idle.

See [1] for a more detailed overview of the problem and of the 
solutions implemented in this patch series. There you will also find 
some preliminary performance results.

Thanks,
Paolo

[1] 
https://secure-web.cisco.com/1hcxnN1C3h1nW7mby7S66_LE8szirQwbQI0fBpYeP
rA0GTWfyuQyl0GpZaOn32xMSkNT0BUQWloDHFzZ23aYDZdi8NfdrEFLY9pQDBblIvn08LR
iTVoIOUC8zWSG_r2PCyLtx3ppZq5cWOib_8azxteRRcbKWGdbLPSqg9hfSJSqltth0ByLO
NHEoI3p3e9QNIn6nVAeQbsT3aOQe-F95XrQvaPrFJXx6RGL9kDXyfkbXIHcdcLBf895gYB
Fn5S2WjBDQq2kzDzZOlc1HekRUhg0qDQcFY6NydVfrqNfLbpAHAth6KyREscQhVTMVREEV
a1b6bQByX6grF5pn3pTIo0lODyfX6yRmcbReSYNfOZ65ZPvp-nH530FQ-5nXoRxFf74WIK
DrNTALs3xQvg03DH4jLez-T2M9xEu-sfEDAEdTGF7BcnmBW6vrPO4_p3k4/https%3A%2F
%2Fwww.linaro.org%2Fblog%2Fbudget-fair-queueing-bfq-linux-io-scheduler
-optimizations-for-multi-actuator-sata-hard-drives%2F

Davide Zini (3):
block, bfq: split also async bfq_queues on a per-actuator basis  
block, bfq: inject I/O to underutilized actuators  block, bfq: balance 
I/O injection among underutilized actuators

Federico Gavioli (1):
block, bfq: retrieve independent access ranges from request queue

Paolo Valente (4):
block, bfq: split sync bfq_queues on a per-actuator basis  block, 
bfq: forbid stable merging of queues associated with different
  actuators
block, bfq: turn scalar fields into arrays in bfq_io_cq  block, bfq: 
turn BFQ_NUM_ACTUATORS into BFQ_MAX_ACTUATORS

block/bfq-cgroup.c  |  97 +++++----
block/bfq-iosched.c | 488 +++++++++++++++++++++++++++++---------------
block/bfq-iosched.h | 149 ++++++++++----
block/bfq-wf2q.c    |   2 +-
4 files changed, 493 insertions(+), 243 deletions(-)

--
2.20.1


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