> >On Wed, Jul 12, 2017 at 10:38:30AM +0000, Bodireddy, Bhanuprakash wrote: >> Hi Ben, >> >> >On Thu, Jun 22, 2017 at 10:10:49PM +0100, Bhanuprakash Bodireddy wrote: >> >> pkt_metadata_init() is called for every packet in userspace >> >> datapath and initializes few members in pkt_metadata. Before this >> >> the members that needs to be initialized are prefetched using >> >pkt_metadata_prefetch_init(). >> >> >> >> The above functions are critical to the userspace datapath >> >> performance and should be in sync. Any changes to the pkt_metadata >> >> should also include changes to metadata_init() and prefetch_init() if >necessary. >> >> >> >> This commit slightly refactors the pkt_metadata structure and >> >> introduces cache line markers to catch any violations to the >> >> structure. Also only prefetch the cachelines having the members >> >> that needs >> >to be zeroed out. >> >> >> >> Signed-off-by: Bhanuprakash Bodireddy >> >> <[email protected]> >> > >> >OVS has a PADDED_MEMBERS macro that makes this easier. >Unfortunately >> >it isn't currently adequate for use more than once per struct. But >> >it's fixable, so I sent a patch to fix it: >> > >> >https://mail.openvswitch.org/pipermail/ovs-dev/2017-July/335204.html >> >> Thanks for this patch. PADDED_MEMBERS macro is pretty handy. >> >> >and a fixed-up version of the original patch: >> > >> >https://mail.openvswitch.org/pipermail/ovs-dev/2017-July/335205.html >> >> Thanks for improving the patch. >> >> > >> >However, even with the fix, this is going to cause problems with >> >MSVC, because it does not allow 0-length arrays. Maybe you can find >> >another way to mark the beginning of a cache line. >> >> Microsoft links mentions that the warning "zero-sized array in >> struct/union" we encountered is a 'Level-4' warning and is numbered >'C4200'. >> >> C4200: https://msdn.microsoft.com/en-us/library/79wf64bc.aspx >> >> I can't think of alternate ways to mark the cachelines, so how about >> this incremental change in lib/util.h that disables the warning when building >with MSVC? >> >> I am currently on vacation and have limited access to lab to download and >test the changes with Microsoft compiliers. >> Apologies for this. >> >> --8<--------------------------cut here-------------------------->8-- >> >> #define CACHE_LINE_SIZE 64 >> BUILD_ASSERT_DECL(IS_POW2(CACHE_LINE_SIZE)); >> #ifndef _MSC_VER >> typedef void *OVS_CACHE_LINE_MARKER[0]; #else __pragma >(warning(push)) >> __pragma (warning(disable:4200)) typedef void >> *OVS_CACHE_LINE_MARKER[0]; __pragma (warning(pop)) #endif >> >> - Bhanuprakash. > >I doubt that this is about a warning, because as I understand it OVS on MSVC >causes a lot of warnings, so it's probably a more serious issue.
In will try to get MSVC installed and verify the OvS build. Will get back to you on this. - Bhanuprakash. _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
