As Kostya said, ASan overhead is not limited to instrumentation of memory access instructions. One other case that comes to mind: too many unique malloc/free stack traces can put pressure on StackDepot.
I'd recommend looking at some of the outliers with a CPU profiler. On Mon, Sep 3, 2018 at 10:53 PM, Konstantin Serebryany <konstantin.s.serebry...@gmail.com> wrote: > Hi Guilherme, > > Instrumenting all memory accesses is only one cause of slowdown. > Another equally important cause is poisoning the heap memory on malloc/free > and poisoning the stack memory on function entry/exit. > Yet another one, is the growth of total memory usage due to redzones and > quarantine (extra RAM usage typically costs extra CPU cycles) > If you don't look at these factors you are unlikely to get a good model. > > > > --kcc > > On Mon, Sep 3, 2018 at 12:28 PM Guilherme <guilhermeleo...@gmail.com> wrote: >> >> Hi all, >> >> We are running a few experiments to try to predict the performance >> slowdown of Address Sanitizer. Our hypothesis is that an executable with >> more memory accesses would take longer than one with fewer. We tried to >> correlate the number of loads/stores in the LLVM IR with the slowdown >> introduced by ASAN but the correlation we've found is too weak to support >> our hypothesis. >> >> I am attaching a chart showing the correlation we've computed. We've used >> the following notation: >> >> time_ratio = (time without asan) / (time with asan) >> stores_visible = stores_instructions_IR / stores_total >> loads_visible = loads_instructions_IR / loads_total >> >> However, the hypothesis still makes sense for us. Therefore, we think we >> might be missing a few factors. So, if we would like to predict the ASAN >> performance overhead on a program, which instructions, other than >> loads/stores, are more likely to cause Address Sanitizer to slowdown the >> program? >> >> Regards, >> >> Guilherme >> >> -- >> You received this message because you are subscribed to the Google Groups >> "address-sanitizer" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to address-sanitizer+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. > > -- > You received this message because you are subscribed to the Google Groups > "address-sanitizer" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to address-sanitizer+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "address-sanitizer" group. To unsubscribe from this group and stop receiving emails from it, send an email to address-sanitizer+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
