netdev - Re: Poor Loopback Interface Performance

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Message-ID: <CAHckoCzwYqbwfyQ07rAtNhWKXdAPOUym78ZiLrKYBYquMfYqNA@mail.gmail.com>
Date:   Fri, 21 Jun 2019 16:13:38 +0800
From:   Li Feng <fengli@...rtx.com>
To:     Storage Performance Development Kit <spdk@...ts.01.org>,
        netdev@...r.kernel.org
Subject: Re: Poor Loopback Interface Performance

Correct CC netdev@...r.kernel.org.

Thanks,

Feng Li

Li Feng <fengli@...rtx.com> 于2019年6月21日周五 下午4:07写道：
>
> Hi, SPDK & Netdev,
>
> When running fio with SPDK iscsi target,
> we find the localhost interface has a bad performance,
> contrast to access from the remote node.
> After upgrade the kernel to 5.1, this issue still exists.
>
>
> There are some fio data of 4k randread, QD=128, jobs = 1:
> iSCSI server run on the NODE1, fio run on NODE1 or NODE2.
>
> Fio +  localhost(NODE1) + openiscsi + SPDK + NVMe
> (3.10.0-693.11.6.el7)          62k
> Fio +  localhost(NODE1) + openiscsi + SPDK + NVMe (5.1 kernel)
>                 86k
> Fio + remote node(NODE2) + openiscsi + SPDK + NVMe
> (3.10.0-693.11.6.el7)    120k
>
> Try 1:
> Connect localhost target with another interface ip (e.g. 10.0.xx.yy),
> the performance is poor. The kernel driver could recognize this is a
> local access, and use loopback directly.
>
> Try 2:
> Setup a new namespace, and add another interface in this ns, and iSCSI
> target listen on this interface.
> Openiscsi connects from the current host, the performance is good.
>
> Question:
> 1. Is this a known issue about the loopback? Any workaround?
> 2. If this is no solution about loopback, how do we force the local
> interface(127.0.0.1, and other nic interfaces) over the wire, not
> directly pass in the host?
>
> Thanks,
> Feng Li

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