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Date: Sat, 13 Apr 2013 20:49:56 -0400 From: Willem de Bruijn <willemb@...gle.com> To: David Miller <davem@...emloft.net> Cc: Daniel Borkmann <dborkman@...hat.com>, Paul Chavent <paul.chavent@...ra.fr>, Richard Cochran <richardcochran@...il.com>, Eric Dumazet <edumazet@...gle.com>, daniel.borkmann@....ee.ethz.ch, xemul@...allels.com, ebiederm@...ssion.com, netdev@...r.kernel.org Subject: Re: [PATCH] net-packet: tx timestamping on tpacket ring On Sat, Apr 13, 2013 at 8:16 PM, Willem de Bruijn <willemb@...gle.com> wrote: > On Sat, Apr 13, 2013 at 8:04 PM, Willem de Bruijn <willemb@...gle.com> wrote: >> On Sat, Apr 13, 2013 at 6:47 PM, David Miller <davem@...emloft.net> wrote: >>> From: Daniel Borkmann <dborkman@...hat.com> >>> Date: Sun, 14 Apr 2013 00:18:48 +0200 >>> >>>>> + flush_dcache_page(pgv_to_page(&h1->tp_sec)); >>>>> + flush_dcache_page(pgv_to_page(&h1->tp_usec)); >>>> >>>> Hmm, not sure, but could we also flush the dcache only once? >>> >>> Indeed, I truly hope that headers never straddle pages. >> >> I should have checked the alignment restrictions on frames. Frames >> must be a multiple of 16 B as well as larger than the header (obviously), >> so this can indeed never happen. > > Actually, 48 B is a multiple of 16, so should be accepted, and 85 > frames on a page leaves half a frame for the next. I'll check whether > this is right. Even if so, it would still not matter for these time > offsets, as they start at 16 or 20 B offset from the start of the > frame. 48 B is too small (Because less than TPACKET_HDRLEN), but it can be triggered with 80 B frames. Daniel, thanks for submitting the selftest: both the timestamp and this alignment question were now very easy to test by just changing a few lines in your code. -- 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
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