Thread: Re: Improve CRC32C performance on SSE4.2
Jesper Pedersen <jesperpedersen.db@gmail.com> writes: Hi, Thank you Nathan, Tomas and Jesper for the answers. The patch at [0] works for me and I could work with master smoothly now. > On 6/14/25 9:56 AM, Nathan Bossart wrote: >> I'm also genuinely curious why folks are using -O0... >> > > Personally, I use > > -O0 -fno-omit-frame-pointer > > for FlameGraph [1] investigations. Same here. I use clang as compiler because I use clangd for code indexing, gcc sometimes use different compiler options which may broke it. I used '-O0' in my daily coding and only use '-O2' when doing some performance testing. [0] https://www.postgresql.org/message-id/CANWCAZbsuavqUK4tg6UF-0-GVRMaq7BafUx4%2BDyd12y%3D-AuFAA%40mail.gmail.com -- Best Regards Andy Fan
On Sun, Jun 15, 2025 at 8:32 AM Andy Fan <zhihuifan1213@163.com> wrote: > > Jesper Pedersen <jesperpedersen.db@gmail.com> writes: > > Hi, > > Thank you Nathan, Tomas and Jesper for the answers. The patch at [0] > works for me and I could work with master smoothly now. Pushed, thanks for testing! I'll do some more testing to see what versions/levels are affected and file a bug report, but it'll be a few days before I get to it. -- John Naylor Amazon Web Services
Attached is a simple reproducer. It passes with clang v16 -O0, but fails with 17 and 18 only when built with -O0. Build command: clang main.c -O0 Hope this helps. Raghuveer > -----Original Message----- > From: John Naylor <johncnaylorls@gmail.com> > Sent: Sunday, June 15, 2025 7:39 PM > To: Andy Fan <zhihuifan1213@163.com> > Cc: Jesper Pedersen <jesperpedersen.db@gmail.com>; Nathan Bossart > <nathandbossart@gmail.com>; Tomas Vondra <tomas@vondra.me>; Devulapalli, > Raghuveer <raghuveer.devulapalli@intel.com>; pgsql- > hackers@lists.postgresql.org; Shankaran, Akash <akash.shankaran@intel.com> > Subject: Re: Improve CRC32C performance on SSE4.2 > > On Sun, Jun 15, 2025 at 8:32 AM Andy Fan <zhihuifan1213@163.com> wrote: > > > > Jesper Pedersen <jesperpedersen.db@gmail.com> writes: > > > > Hi, > > > > Thank you Nathan, Tomas and Jesper for the answers. The patch at [0] > > works for me and I could work with master smoothly now. > > Pushed, thanks for testing! I'll do some more testing to see what versions/levels > are affected and file a bug report, but it'll be a few days before I get to it. > > -- > John Naylor > Amazon Web Services >