From: Joerg Roedel <joro@8bytes.org>
To: Jakub Kicinski <kuba@kernel.org>,
Vasant Hegde <vasant.hegde@amd.com>,
Robin Murphy <robin.murphy@arm.com>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
iommu@lists.linux.dev,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Willem de Bruijn <willemb@google.com>,
Saeed Mahameed <saeed@kernel.org>
Subject: Re: AMD IOMMU problem after NIC uses multi-page allocation
Date: Thu, 30 Mar 2023 09:41:29 +0200 [thread overview]
Message-ID: <ZCU9KZMlGMWb2ezZ@8bytes.org> (raw)
In-Reply-To: <20230329181407.3eed7378@kernel.org>
Also adding Vasant and Robin.
Vasant, Robin, any idea?
On Wed, Mar 29, 2023 at 06:14:07PM -0700, Jakub Kicinski wrote:
> Hi Joerg, Suravee,
>
> I see an odd NIC behavior with AMD IOMMU in lazy mode (on 5.19).
>
> The NIC allocates a buffer for Rx packets which is MTU rounded up
> to page size. If I run it with 1500B MTU or 9000 MTU everything is
> fine, slight but manageable perf hit.
>
> But if I flip the MTU to 9k, run some traffic and then go back to 1.5k
> - 70%+ of CPU cycles are spent in alloc_iova (and children).
>
> Does this ring any bells?
next prev parent reply other threads:[~2023-03-30 7:41 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-30 1:14 AMD IOMMU problem after NIC uses multi-page allocation Jakub Kicinski
2023-03-30 2:36 ` Yunsheng Lin
2023-03-30 7:41 ` Joerg Roedel [this message]
2023-03-30 12:07 ` Vasant Hegde
2023-03-30 13:04 ` Robin Murphy
2023-03-30 13:10 ` Robin Murphy
2023-03-31 4:06 ` Jakub Kicinski
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