Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the timecompare method

On Wed, Mar 21, 2012 at 1:09 PM, Keller, Jacob E
[off-list ref] wrote:

quoted

-----Original Message-----
From: Richard Cochran [mailto:richardcochran@gmail.com]
Sent: Wednesday, March 21, 2012 10:00 AM
To: chetan loke
Cc: netdev@vger.kernel.org; e1000-devel@lists.sourceforge.net; Keller, Jacob
E; Kirsher, Jeffrey T; Ronciak, John; john.stultz@linaro.org;
tglx@linutronix.de
Subject: Re: [PATCH net V4 2/2] igb: offer a PTP Hardware Clock instead of the
timecompare method

Can you please explain how using a seqlock could help here?

Thanks,
Richard

My understanding of the seqlock, is that it prevents starvation of the hwtstamp calls in the rx and tx routines if/when a user hammers the gettime ioctl due to bad software design where 100+ apps are wanting direct access to the PHC.

Richard - Intent is to make the readers(get_time) wait (or return last
read value if the seq_counter tripped because you know that this value
was recent) and let the tx/rx path continue. I haven't looked in more
details but as Jake mentioned you will also need to change the way you
read the values(by not using timecounter_read in get_time).

thanks
Chetan

------------------------------------------------------------------------------
This SF email is sponsosred by:
Try Windows Azure free for 90 days Click Here 
http://p.sf.net/sfu/sfd2d-msazure
_______________________________________________
E1000-devel mailing list
E1000-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/e1000-devel
To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired