From: Jussi Maki <joamaki@gmail.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
jroedel@suse.de, netdev@vger.kernel.org,
bpf <bpf@vger.kernel.org>,
intel-wired-lan@lists.osuosl.org, davem@davemloft.net,
anthony.l.nguyen@intel.com, jesse.brandeburg@intel.com,
hch@lst.de, iommu@lists.linux-foundation.org,
suravee.suthikulpanit@amd.com, gregkh@linuxfoundation.org
Subject: Re: Regression 5.12.0-rc4 net: ice: significant throughput drop
Date: Thu, 3 Jun 2021 14:32:35 +0200 [thread overview]
Message-ID: <CAHn8xc=1g8bzV-uxaJAYpJ114rR7MLzth=4jyDG329ZwEG+kpg@mail.gmail.com> (raw)
In-Reply-To: <705f90c3-b933-8863-2124-3fea7fdbd81a@arm.com>
On Wed, Jun 2, 2021 at 2:49 PM Robin Murphy <robin.murphy@arm.com> wrote:
> >> Thanks for the quick response & patch. I tried it out and indeed it
> >> does solve the issue:
>
> Cool, thanks Jussi. May I infer a Tested-by tag from that?
Of course!
> Given that the race looks to have been pretty theoretical until now, I'm
> not convinced it's worth the bother of digging through the long history
> of default domain and DMA ops movement to figure where it started, much
> less attempt invasive backports. The flush queue change which made it
> apparent only landed in 5.13-rc1, so as long as we can get this in as a
> fix in the current cycle we should be golden - in the meantime, note
> that booting with "iommu.strict=0" should also restore the expected
> behaviour.
>
> FWIW I do still plan to resend the patch "properly" soon (in all honesty
> it wasn't even compile-tested!)
BTW, even with the patch there's quite a bit of spin lock contention
coming from ice_xmit_xdp_ring->dma_map_page_attrs->...->alloc_iova.
CPU load drops from 85% to 20% (~80Mpps, 64b UDP) when iommu is
disabled. Is this type of overhead to be expected?
next prev parent reply other threads:[~2021-06-03 12:34 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-28 8:34 Regression 5.12.0-rc4 net: ice: significant throughput drop Jussi Maki
2021-06-01 6:57 ` Daniel Borkmann
2021-06-01 12:39 ` Robin Murphy
2021-06-01 17:42 ` Jussi Maki
2021-06-02 8:09 ` Daniel Borkmann
2021-06-02 12:48 ` Robin Murphy
2021-06-03 12:32 ` Jussi Maki [this message]
2021-06-03 13:09 ` Robin Murphy
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