On Tue, May 26, 2020 at 12:42:16PM +0200, Arnd Bergmann wrote: > On Thu, May 21, 2020 at 10:21 PM 'Nick Desaulniers' via Clang Built > Linux <[email protected]> wrote: > > > > On Thu, May 21, 2020 at 7:22 AM 'Marco Elver' via Clang Built Linux > > <[email protected]> wrote: > > > > > > It appears that compilers have trouble with nested statement > > > expressions. Therefore remove one level of statement expression nesting > > > from the data_race() macro. This will help us avoid potential problems > > > in future as its usage increases. > > > > > > Link: https://lkml.kernel.org/r/[email protected] > > > Acked-by: Will Deacon <[email protected]> > > > Signed-off-by: Marco Elver <[email protected]> > > > > Thanks Marco, I can confirm this series fixes the significant build > > time regressions. > > > > Tested-by: Nick Desaulniers <[email protected]> > > > > More measurements in: https://github.com/ClangBuiltLinux/linux/issues/1032 > > > > Might want: > > Reported-by: Borislav Petkov <[email protected]> > > Reported-by: Nathan Chancellor <[email protected]> > > too. > > I find this patch only solves half the problem: it's much faster than > without the > patch, but still much slower than the current mainline version. As far as I'm > concerned, I think the build speed regression compared to mainline is not yet > acceptable, and we should try harder. > > I have not looked too deeply at it yet, but this is what I found from looking > at a file in a randconfig build: > > Configuration: see https://pastebin.com/raw/R9erCwNj
So this .config actually has KCSAN enabled. Do you still see the slowdown with that disabled? Although not ideal, having a longer compiler time when the compiler is being asked to perform instrumentation doesn't seem like a show-stopper to me. Will
