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 >> <bhanuprakash.bodire...@intel.com> > >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. _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
