From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: Xiao Ni <xni@redhat.com>,
linux-raid@vger.kernel.org, Jes Sorensen <jes@trained-monkey.org>,
Guoqing Jiang <guoqing.jiang@linux.dev>,
Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>,
Coly Li <colyli@suse.de>,
Chaitanya Kulkarni <chaitanyak@nvidia.com>,
Jonmichael Hands <jm@chia.net>,
Stephen Bates <sbates@raithlin.com>,
Martin Oliveira <Martin.Oliveira@eideticom.com>,
David Sloan <David.Sloan@eideticom.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH mdadm v4 0/7] Write Zeroes option for Creating Arrays
Date: Wed, 12 Oct 2022 21:33:51 -0400 [thread overview]
Message-ID: <yq15ygo4jkv.fsf@ca-mkp.ca.oracle.com> (raw)
In-Reply-To: <8ee5368c-1808-d2bc-9ad2-2f8332d2704e@deltatee.com> (Logan Gunthorpe's message of "Wed, 12 Oct 2022 10:59:45 -0600")
Logan,
> 2) We could split up the fallocate call into multiple calls to zero
> the entire disk. This would allow a quicker ctrl-c to occur, however
> it's not clear what the best size would be to split it into. Even
> zeroing 1GB can take a few seconds,
FWIW, we default to 32MB per request in SCSI unless the device
explicitly advertises wanting something larger.
> (with NVMe, discard only requires a single command to handle the
> entire disk
In NVMe there's a limit of 64K blocks per range and 256 ranges per
request. So 8GB or 64GB per request for discard depending on the block
size. So presumably it will take several operations to deallocate an
entire drive.
> where as write-zeroes requires a minimum of one command per 2MB of
> data to zero).
32MB for 512-byte blocks and 256MB for 4096-byte blocks. Which matches
how it currently works for SCSI devices.
> I was hoping write-zeroes could be made faster in the future, at least
> for NVMe.
Deallocate had a bit of a head start and vendors are still catching up
in the zeroing department. Some drives do support using Deallocate for
zeroing and we quirk those in the driver so they should perform OK with
your change.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2022-10-13 1:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-07 20:10 [PATCH mdadm v4 0/7] Write Zeroes option for Creating Arrays Logan Gunthorpe
2022-10-07 20:10 ` [PATCH mdadm v4 1/7] Create: goto abort_locked instead of return 1 in error path Logan Gunthorpe
2022-10-07 20:10 ` [PATCH mdadm v4 2/7] Create: remove safe_mode_delay local variable Logan Gunthorpe
2022-10-07 20:10 ` [PATCH mdadm v4 3/7] Create: Factor out add_disks() helpers Logan Gunthorpe
2022-10-07 20:10 ` [PATCH mdadm v4 4/7] mdadm: Introduce pr_info() Logan Gunthorpe
2022-10-07 20:10 ` [PATCH mdadm v4 5/7] mdadm: Add --write-zeros option for Create Logan Gunthorpe
2022-10-07 20:10 ` [PATCH mdadm v4 6/7] tests/00raid5-zero: Introduce test to exercise --write-zeros Logan Gunthorpe
2022-10-07 20:10 ` [PATCH mdadm v4 7/7] manpage: Add --write-zeroes option to manpage Logan Gunthorpe
2022-10-12 1:09 ` [PATCH mdadm v4 0/7] Write Zeroes option for Creating Arrays Xiao Ni
2022-10-12 16:59 ` Logan Gunthorpe
2022-10-13 1:33 ` Martin K. Petersen [this message]
2022-10-13 7:51 ` Xiao Ni
2022-10-26 2:41 ` Martin K. Petersen
2022-10-27 8:44 ` Xiao Ni
2022-11-16 17:11 ` Logan Gunthorpe
2022-11-03 8:14 ` Kinga Tanska
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