lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 22 Dec 2020 12:41:14 +0800
From:   Jason Wang <>
To:     Willem de Bruijn <>,
        wangyunjian <>
Cc:     Network Development <>,
        "Michael S. Tsirkin" <>,,
        "Lilijun (Jerry)" <>,
        chenchanghu <>,
        xudingke <>,
        "huangbin (J)" <>
Subject: Re: [PATCH net v2 2/2] vhost_net: fix high cpu load when sendmsg

On 2020/12/22 上午7:07, Willem de Bruijn wrote:
> On Wed, Dec 16, 2020 at 3:20 AM wangyunjian<>  wrote:
>> From: Yunjian Wang<>
>> Currently we break the loop and wake up the vhost_worker when
>> sendmsg fails. When the worker wakes up again, we'll meet the
>> same error.
> The patch is based on the assumption that such error cases always
> return EAGAIN. Can it not also be ENOMEM, such as from tun_build_skb?
>> This will cause high CPU load. To fix this issue,
>> we can skip this description by ignoring the error. When we
>> exceeds sndbuf, the return value of sendmsg is -EAGAIN. In
>> the case we don't skip the description and don't drop packet.
> the -> that
> here and above: description -> descriptor
> Perhaps slightly revise to more explicitly state that
> 1. in the case of persistent failure (i.e., bad packet), the driver
> drops the packet
> 2. in the case of transient failure (e.g,. memory pressure) the driver
> schedules the worker to try again later

If we want to go with this way, we need a better time to wakeup the 
worker. Otherwise it just produces more stress on the cpu that is what 
this patch tries to avoid.



Powered by blists - more mailing lists