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Date: Fri, 22 Nov 2024 11:16:31 -0700
From: Keith Busch <kbusch@kernel.org>
To: John Meneghini <jmeneghi@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>, Bryan Gurney <bgurney@redhat.com>,
	linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	sagi@grimberg.me, axboe@kernel.dk, mpe@ellerman.id.au,
	naveen@kernel.org, maddy@linux.ibm.com, kernel@xen0n.name,
	bmarzins@redhat.com
Subject: Re: [PATCH 1/1] nvme: always enable multipath
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On Fri, Nov 22, 2024 at 12:52:51PM -0500, John Meneghini wrote:
> On 11/22/24 10:39, Keith Busch wrote:
> > Anyway, we only use the one physical function, so they're certainly not
> > multipath devices here. We disable the CONFIG option because while the
> > nvme multipath IO overhead is low, it's not zero.
> 
> Do we know what the performance impact is?  Has anybody measured the difference?

It doesn't benefit single path devices, so any cost for it is too high.
It's clearly not free.