Date: Mon, 20 Oct 2014 18:13:38 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-net@FreeBSD.org Subject: [Bug 194314] [ixgbe] driver makes some dangerous assumptions with struct mbuf sizing with IXGBE_RX_COPY_LEN Message-ID: <bug-194314-2472-ofdNA1Fc5e@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-194314-2472@https.bugs.freebsd.org/bugzilla/> References: <bug-194314-2472@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=194314 --- Comment #12 from Eric Joyner <ricera10@gmail.com> --- (In reply to Garrett Cooper from comment #10) > (In reply to Eric Joyner from comment #8) > > So it sounds like we may just need to change IXGBE_RX_COPY_LEN from a fixed > > value of 160 to something that's calculated based on the length of struct > > m_hdr and struct m_pkthdr combined. > > > > I think they got 160 by adding together the size of the two header structs > > (88 in FreeBSD amd64), adding some number (8) to make that size divisible by > > 32 (96 % 32 == 0), and then subtracted that from MSIZE (256) to get > > IXGBE_RX_COPY_LEN (160), while keeping the padding added as > > IXGBE_RX_COPY_ALIGN. > > A couple questions then: > > - What architectures is this driver supported on? > - Is this optimization only valid for amd64? > - Why 32? - At least i386 and amd64, but it should theoretically work on anything with a PCI-E slot - This optimization specifically was contributed by scottl/luigi, looking at the commit logs. You should ask either of those two for details. - Doesn't the comment in the code you posted answer that? -- You are receiving this mail because: You are the assignee for the bug.
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