linux-kernel - Re: [RFC PATCH 00/17] virtual-bus

lists.openwall.net		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 linux-cve-announce 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]

Message-ID: <49D4CC61.6010105@redhat.com>
Date:	Thu, 02 Apr 2009 17:32:01 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Gregory Haskins <ghaskins@...ell.com>
CC:	Anthony Liguori <anthony@...emonkey.ws>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	agraf@...e.de, pmullaney@...ell.com, pmorreale@...ell.com,
	rusty@...tcorp.com.au, netdev@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [RFC PATCH 00/17] virtual-bus

Gregory Haskins wrote:
>> If you have a request-response workload with the wire idle and latency
>> critical, then there's no problem having an exit per packet because
>> (a) there aren't that many packets and (b) the guest isn't doing any
>> batching, so guest overhead will swamp the hypervisor overhead.
>>     
> Right, so the trick is to use an algorithm that adapts here.  Batching
> solves the first case, but not the second.  The bidir napi thing solves
> both, but it does assume you have ample host processing power to run the
> algorithm concurrently.  This may or may not be suitable to all
> applications, I admit.
>   

The alternative is to get a notification from the stack that the packet 
is done processing.  Either an skb destructor in the kernel, or my new 
API that everyone is not rushing out to implement.

>>> Right now its way way way worse than 2us.  In fact, at my last reading
>>> this was more like 3060us (3125-65).  So shorten that 3125 to 67 (while
>>> maintaining line-rate) and I will be impressed.  Heck, shorten it to
>>> 80us and I will be impressed.
>>>   
>>>       
>> The 3060us thing is a timer, not cpu time.
>>     
> Agreed, but its still "state of the art" from an observer perspective. 
> The reason "why", though easily explainable, is inconsequential to most
> people.  FWIW, I have seen virtio-net do a much more respectable 350us
> on an older version, so I know there is plenty of room for improvement.
>   

All I want is the notification, and the timer is headed into the nearest 
landfill.


-- 
error compiling committee.c: too many arguments to function

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/