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Subject: Re: [PATCH 0/8] block, bfq: extend bfq to support multi-actuator
 drives
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <SJ0PR20MB44093D6FB740E543EDAAC002A0629@SJ0PR20MB4409.namprd20.prod.outlook.com>
Date:   Wed, 10 Aug 2022 12:22:55 +0200
Cc:     Arie van der Hoeven <arie.vanderhoeven@seagate.com>,
        Muhammad Ahmad <muhammad.ahmad@seagate.com>,
        "linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Jan Kara <jack@suse.cz>,
        "andrea.righi@canonical.com" <andrea.righi@canonical.com>,
        "glen.valante@linaro.org" <glen.valante@linaro.org>,
        "axboe@kernel.dk" <axboe@kernel.dk>,
        Tyler Erickson <tyler.erickson@seagate.com>,
        Michael English <michael.english@seagate.com>,
        Andrew Ring <andrew.ring@seagate.com>,
        Varun Boddu <varunreddy.boddu@seagate.com>
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Message-Id: <74F8D5E8-0D56-413B-A3CA-7462D9C862D6@linaro.org>
References: <20220623155335.6147-1-paolo.valente@linaro.org>
 <PH7PR20MB505849512979A89E8A66FB24F18E9@PH7PR20MB5058.namprd20.prod.outlook.com>
 <SJ0PR20MB44093D6FB740E543EDAAC002A0629@SJ0PR20MB4409.namprd20.prod.outlook.com>
To:     Rory Chen <rory.c.chen@seagate.com>
Precedence: bulk


> Il giorno 9 ago 2022, alle ore 05:47, Rory Chen =
<rory.c.chen@seagate.com> ha scritto:
>=20
> 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)
>=20
> Hi Paolo,
>=20

Hi

> I am from Seagate China and face a problem when I=E2=80=99m evaluating =
the bfq patches. Could you please check?
> Thanks
>=20
> Issue statement
> When running performance test on bfq patch, I observed warning message =
"bfq_actuator_index: bio sector out of ranges: end=3D35156656128" 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=E2=80=99s beyond the LBA range.

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

>  I captured the block trace and didn=E2=80=99t 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.

> I=E2=80=99m not sure if this warning message is related to later OS =
hung.
>=20

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

>=20
> 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]
>=20
>=20
>=20
>=20
>=20
> From: Paolo Valente <paolo.valente@linaro.org>
> Sent: Thursday, June 23, 2022 8:53 AM
> To: Jens Axboe <axboe@kernel.dk>
> Cc: linux-block@vger.kernel.org <linux-block@vger.kernel.org>; =
linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>; =
jack@suse.cz <jack@suse.cz>; andrea.righi@canonical.com =
<andrea.righi@canonical.com>; glen.valante@linaro.org =
<glen.valante@linaro.org>; Arie van der Hoeven =
<arie.vanderhoeven@seagate.com>; Paolo Valente =
<paolo.valente@linaro.org>
> Subject: [PATCH 0/8] block, bfq: extend bfq to support multi-actuator =
drives
>=20
>=20
> This message has originated from an External Source. Please use proper =
judgment and caution when opening attachments, clicking links, or =
responding to this email.
>=20
>=20
> 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=E2=80=99s 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.
>=20
> 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.
>=20
> 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.
>=20
> Thanks,
> Paolo
>=20
> [1] =
https://secure-web.cisco.com/1hcxnN1C3h1nW7mby7S66_LE8szirQwbQI0fBpYePrA0G=
TWfyuQyl0GpZaOn32xMSkNT0BUQWloDHFzZ23aYDZdi8NfdrEFLY9pQDBblIvn08LRiTVoIOUC=
8zWSG_r2PCyLtx3ppZq5cWOib_8azxteRRcbKWGdbLPSqg9hfSJSqltth0ByLONHEoI3p3e9QN=
In6nVAeQbsT3aOQe-F95XrQvaPrFJXx6RGL9kDXyfkbXIHcdcLBf895gYBFn5S2WjBDQq2kzDz=
ZOlc1HekRUhg0qDQcFY6NydVfrqNfLbpAHAth6KyREscQhVTMVREEVa1b6bQByX6grF5pn3pTI=
o0lODyfX6yRmcbReSYNfOZ65ZPvp-nH530FQ-5nXoRxFf74WIKDrNTALs3xQvg03DH4jLez-T2=
M9xEu-sfEDAEdTGF7BcnmBW6vrPO4_p3k4/https%3A%2F%2Fwww.linaro.org%2Fblog%2Fb=
udget-fair-queueing-bfq-linux-io-scheduler-optimizations-for-multi-actuato=
r-sata-hard-drives%2F
>=20
> 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
>=20
> Federico Gavioli (1):
>  block, bfq: retrieve independent access ranges from request queue
>=20
> 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
>=20
> 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(-)
>=20
> --
> 2.20.1
>=20
>=20
> Seagate Internal
>=20
> Seagate Internal