netdev - Re: [Xen-devel] [PATCHv1] xen-netfront: always keep the Rx ring full of requests

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: <542D5963.10104@citrix.com>
Date:	Thu, 2 Oct 2014 14:55:47 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Jan Beulich <JBeulich@...e.com>
CC:	<xen-devel@...ts.xenproject.org>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	<netdev@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCHv1] xen-netfront: always keep the Rx ring full
 of requests

On 02/10/14 14:46, Jan Beulich wrote:
>>>> On 02.10.14 at 15:33, <david.vrabel@...rix.com> wrote:
>> A full Rx ring only requires 1 MiB of memory.  This is not enough
>> memory that it is useful to dynamically scale the number of Rx
>> requests in the ring based on traffic rates.
> 
> The performance benefits are nice, but does the above statement
> scale to hundreds of guests with perhaps multiple NICs and/or
> queues?

Yes, because:

a) Even the full 1 MiB is a tiny fraction of a typically modern Linux VM
(for example, the AWS micro instance still has 1 GiB of memory).

b) Netfront would have used up to 1 MiB already even with moderate data
rates (there was no adjustment of target based on memory pressure).

c) Small VMs are going to typically have one VCPU and hence only one queue.

David
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html