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 <3d1834d9-7905-1225-741a-f298dd5b8a8e@linux.dev> <Y6TSgGdCTvkwPiVg@kbusch-mbp.dhcp.thefacebook.com>
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From:   Xinghui Li <korantwork@gmail.com>
Date:   Fri, 23 Dec 2022 16:02:03 +0800
Message-ID: <CAEm4hYUWf+Fx3FV7vNTc8+O9NSb0iQp75MTC6gra6XapXK=cxw@mail.gmail.com>
Subject: Re: [PATCH] PCI: vmd: Do not disable MSI-X remapping in VMD 28C0 controller
To:     Keith Busch <kbusch@kernel.org>
Cc:     Jonathan Derrick <jonathan.derrick@linux.dev>,
        nirmal.patel@linux.intel.com, lpieralisi@kernel.org,
        linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        Xinghui Li <korantli@tencent.com>
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Keith Busch <kbusch@kernel.org> =E4=BA=8E2022=E5=B9=B412=E6=9C=8823=E6=97=
=A5=E5=91=A8=E4=BA=94 05:56=E5=86=99=E9=81=93=EF=BC=9A
>
> With 12 drives and only 6 CPUs, the bypass mode is going to get more irq
> context switching. Sounds like the non-bypass mode is aggregating and
> spreading interrupts across the cores better, but there's probably some
> cpu:drive count tipping point where performance favors the other way.

We found that tunning the interrupt aggregation can also bring the
drive performance back to normal.

> The fio jobs could also probably set their cpus_allowed differently to
> get better performance in the bypass mode.

We used the cpus_allowed in FIO to fix 12 dirves in 6 different CPU.

By the way, sorry for emailing twice, the last one had the format problem.