netdev - Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM virtio-net.

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]

Date:	Mon, 02 Aug 2010 09:01:58 -0700
From:	Shirley Ma <mashirle@...ibm.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	xiaohui.xin@...el.com, netdev@...r.kernel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, mst@...hat.com, mingo@...e.hu,
	davem@...emloft.net, herbert@...dor.hengli.com.au,
	jdike@...ux.intel.com
Subject: Re: [RFC PATCH v8 00/16] Provide a zero-copy method on KVM
 virtio-net.

Hello Avi,

On Sun, 2010-08-01 at 11:18 +0300, Avi Kivity wrote:
> I don't understand.  Under what conditions do you use
> get_user_pages() 
> instead of get_user_pages_fast()?  Why?

The code always calls get_user_pages_fast, however, the page will be
unpinned in skb_free if the same page is not used again for a new
buffer. The reason for unpin the page is we don't want to pin all of the
guest kernel memory(memory over commit). So get_user_pages_fast will
call slow path get_user_pages. 

Your previous comment is suggesting to keep the page pinned for
get_user_pages_fast fast path?

Thanks
Shirley

--
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