Thanks for the explanation Todd and Dan! I had introduced a new CACHELINE_ALIGNED object into the class which caused this problem. Making the parent classes CACHELINE_ALIGNED too fixed the problem.
On Wed, Feb 14, 2018 at 12:58 PM, Todd Lipcon <t...@cloudera.com> wrote: > This probably means that QueryExecMgr (or one of its descendent members) is > annotated with __attribute__((aligned(64)), perhaps through something like > a CACHELINE_ALIGNED macro. > > The issue is that, as the warning says, normal libc malloc doesn't make any > hard guarantees about the alignment of allocations, and the way that > 'operator new' is implemented by default only gets the size and not the > desired allocation. I believe C++17 is adding support for an 'operator new' > overload that also passes the desired alignment, so that it can call down > into posix_memalign and ensure the appropriate allocation. > > The "correct" fix prior to C++17 is probably to do something like overload > 'operator new' for the type, or to use posix_memalign manually to allocate > aligned memory, and then placement-new it into that memory. > > Another reasonable fix would probably be to add a CHECK in the constructor > that 'this' is aligned as desired so that, if you ever run on an allocator > that isn't guaranteeing what you think it is, you'll know immediately > rather than getting a surprising perf or atomicity regression due to > cross-cacheline loads/stores. > > -Todd > > > On Wed, Feb 14, 2018 at 12:33 PM, Sailesh Mukil <sail...@cloudera.com> > wrote: > > > Does anyone have experience with fixing the following type of > > clang-tidy warning? > > > > > > /home/ubuntu/Impala/be/src/runtime/exec-env.cc:159:21: warning: type > > 'impala::QueryExecMgr' requires 64 bytes of alignment and the default > > allocator only guarantees 16 bytes [clang-diagnostic-over-aligned] > > query_exec_mgr_(new QueryExecMgr()), > > > > > > /home/ubuntu/Impala/be/src/service/impalad-main.cc:80:49: warning: > > type 'impala::ImpalaServer' requires 64 bytes of alignment and the > > default allocator only guarantees 16 bytes > > [clang-diagnostic-over-aligned] > > boost::shared_ptr<ImpalaServer> impala_server(new > > ImpalaServer(&exec_env)); > > > > > > -- > Todd Lipcon > Software Engineer, Cloudera >