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From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: Damien Le Moal <Damien.LeMoal@wdc.com>,
	"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
	Jens Axboe <axboe@kernel.dk>,
	"linux-nvme@lists.infradead.org" <linux-nvme@lists.infradead.org>,
	Keith Busch <kbusch@kernel.org>,
	"dm-devel@redhat.com" <dm-devel@redhat.com>,
	Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH] block: Improve io_opt limit stacking
Date: Fri, 22 May 2020 09:36:18 -0400
Message-ID: <yq1ftbsp06e.fsf@ca-mkp.ca.oracle.com> (raw)
In-Reply-To: <yq1lflkp0b9.fsf@ca-mkp.ca.oracle.com> (Martin K. Petersen's message of "Fri, 22 May 2020 09:28:36 -0400")


>>> +	if (t->io_opt & (t->physical_block_size - 1))
>>> +		t->io_opt = lcm(t->io_opt, t->physical_block_size);
>
>> Any comment on this patch ?  Note: the patch the patch "nvme: Fix
>> io_opt limit setting" is already queued for 5.8.
>
> Setting io_opt to the physical block size is not correct.

Oh, missed the lcm(). But I'm still concerned about twiddling io_opt to
a value different than the one reported by an underlying device.

Setting io_opt to something that's less than a full stripe width in a
RAID, for instance, doesn't produce the expected result. So I think I'd
prefer not to set io_opt at all if it isn't consistent across all the
stacked devices.

Let me chew on it for a bit...

-- 
Martin K. Petersen	Oracle Linux Engineering

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-14  6:58 Damien Le Moal
2020-05-22  7:27 ` Damien Le Moal
2020-05-22 13:28   ` Martin K. Petersen
2020-05-22 13:36     ` Martin K. Petersen [this message]
2020-05-22 14:14       ` Keith Busch

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