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
| ||
|
Message-ID: <50287857.2060305@tuffmail.com> Date: Sun, 12 Aug 2012 23:45:27 -0400 From: Robert Vineyard <vineyard@...fmail.com> To: "Michael S. Tsirkin" <mst@...hat.com> CC: Stephen Hemminger <shemminger@...tta.com>, "Peter Huang(Peng)" <peter.huangpeng@...wei.com>, kvm@...r.kernel.org, netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org, avi@...hat.com, xiaohui.xin@...el.com Subject: Re: [Question]About KVM network zero-copy feature! On 08/12/2012 05:37 AM, Michael S. Tsirkin wrote: > AFAIK Xin left Intel and is not working on it. > Contributions are welcome. That's too bad... do you know of anyone else (at Intel or otherwise) who might be familiar enough with the existing codebase to get me started? From the code I've looked at, it appears that among other things they're using the splice(2) / vmsplice(2) system calls to effect "copying" without actually copying data. If I understand the semantics correctly, these calls are basically shuffling pointers around to avoid unnecessary memcpy(3) / mmap(2) calls. I've even seen a "zero-copy" version of sendfile(2) that essentially wraps it around a call to splice(2). I may be able to hack something together based on the current zero-copy TX implementation, but as I'm still wrapping my head around several of the concepts I just described, it may be awhile before I can produce anything useful. I have quite a bit of experience developing for Linux in C, but this would be my first attempt at writing kernel/device-driver code. >> The Release Notes for RHEL 6.2 (originally published on 12/06/2011) >> also specifically mention macvtap/vhost zero-copy capabilities as >> being included as a Technology Preview: >> >> http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/6.2_Release_Notes/virtualization.html > > I think this means TX. It does. I meant to clarify that point in my original email... yes, only TX zero-copy is currently implemented, and it is still marked as "experimental". Outside of the custom solutions like PF_RING that I mentioned, I don't know that I've seen zero-copy for RX. -- Robert Vineyard -- 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
Powered by blists - more mailing lists