Re: [PATCH 1/1] allow using a higher icount

["Alex Bennée" <alex.bennee@linaro.org>]

Elisha Hollander <just4now666666@gmail.com> writes:

> Although it gives `undefined symbol: qemu_plugin_scoreboard_free`. But
> probably I messed something up...

Are you using an older QEMU? We should trigger an API warning if they
are mismatched but maybe thats not working.

>
> On Tue, Aug 27, 2024, 14:59 Elisha Hollander <just4now666666@gmail.com> wrote:
>
>  Oh nice, I didn't know that
>
>  On Tue, Aug 27, 2024, 12:39 Alex Bennée <alex.bennee@linaro.org> wrote:
>
>  Elisha Hollander <just4now666666@gmail.com> writes:
>
>  > Signed-off-by: Elisha Hollander <just4now666666@gmail.com>
>
>  What is the use-case for this patch?
>
>  If you are simply looking to slow the emulated system down please have a
>  look at:
>
>    https://qemu.readthedocs.io/en/master/about/emulation.html#limit-instructions-per-second
>
>  which uses the plugin system to limit the run rate and sleep if its
>  running too fast. The longer term goal is to deprecate the icount clock
>  alignment feature from the core code and leave icount to just provide
>  the deterministic execution needed for record/replay and reverse
>  debugging.
>
>  > ---
>  >  accel/tcg/cpu-exec.c      | 4 +---
>  >  accel/tcg/icount-common.c | 4 ++--
>  >  2 files changed, 3 insertions(+), 5 deletions(-)
>  >
>  > diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
>  > index 8163295f34..4c2baf8ed4 100644
>  > --- a/accel/tcg/cpu-exec.c
>  > +++ b/accel/tcg/cpu-exec.c
>  > @@ -95,11 +95,10 @@ static void align_clocks(SyncClocks *sc, CPUState *cpu)
>  >  static void print_delay(const SyncClocks *sc)
>  >  {
>  >      static float threshold_delay;
>  > -    static int64_t last_realtime_clock;
>  >      static int nb_prints;
>  >  
>  >      if (icount_align_option &&
>  > -        sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
>  > +        sc->diff_clk >= MAX_DELAY_PRINT_RATE &&
>  >          nb_prints < MAX_NB_PRINTS) {
>  >          if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
>  >              (-sc->diff_clk / (float)1000000000LL <
>  > @@ -109,7 +108,6 @@ static void print_delay(const SyncClocks *sc)
>  >                          threshold_delay - 1,
>  >                          threshold_delay);
>  >              nb_prints++;
>  > -            last_realtime_clock = sc->realtime_clock;
>  >          }
>  >      }
>  >  }
>  > diff --git a/accel/tcg/icount-common.c b/accel/tcg/icount-common.c
>  > index 8d3d3a7e9d..f07f8baf4d 100644
>  > --- a/accel/tcg/icount-common.c
>  > +++ b/accel/tcg/icount-common.c
>  > @@ -46,8 +46,8 @@
>  >   * is TCG-specific, and does not need to be built for other accels.
>  >   */
>  >  static bool icount_sleep = true;
>  > -/* Arbitrarily pick 1MIPS as the minimum allowable speed.  */
>  > -#define MAX_ICOUNT_SHIFT 10
>  > +/* Arbitrarily pick the minimum allowable speed.  */
>  > +#define MAX_ICOUNT_SHIFT 30
>  >  
>  >  /* Do not count executed instructions */
>  >  ICountMode use_icount = ICOUNT_DISABLED;
>
>  -- 
>  Alex Bennée
>  Virtualisation Tech Lead @ Linaro

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro