From: Jakub Kicinski <kuba@kernel.org>
To: Joerg Roedel <joro@8bytes.org>,
Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: iommu@lists.linux.dev,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Willem de Bruijn <willemb@google.com>,
Saeed Mahameed <saeed@kernel.org>
Subject: AMD IOMMU problem after NIC uses multi-page allocation
Date: Wed, 29 Mar 2023 18:14:07 -0700 [thread overview]
Message-ID: <20230329181407.3eed7378@kernel.org> (raw)
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 reply other threads:[~2023-03-30 1:14 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-30 1:14 Jakub Kicinski [this message]
2023-03-30 2:36 ` AMD IOMMU problem after NIC uses multi-page allocation Yunsheng Lin
2023-03-30 7:41 ` Joerg Roedel
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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