Quoting Joonas Lahtinen (2017-09-27 09:52:42)
> On Mon, 2017-09-25 at 21:26 +0100, Chris Wilson wrote:
> > Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> > ---
> > benchmarks/gem_syslatency.c | 86
> > +++++++++++++++++++++++++++++++++++++++++++--
> > 1 file changed, 83 insertions(+), 3 deletions(-)
> >
> > diff --git a/benchmarks/gem_syslatency.c b/benchmarks/gem_syslatency.c
> > index 4ed23638..b8788497 100644
> > --- a/benchmarks/gem_syslatency.c
> > +++ b/benchmarks/gem_syslatency.c
> > @@ -29,6 +29,7 @@
> > #include <stdio.h>
> > #include <string.h>
> > #include <fcntl.h>
> > +#include <ftw.h>
> > #include <inttypes.h>
> > #include <pthread.h>
> > #include <sched.h>
> > @@ -51,6 +52,7 @@ static volatile int done;
> > struct gem_busyspin {
> > pthread_t thread;
> > unsigned long count;
> > + bool leak;
> > };
>
> I know we all binary arithmetic, but can I still ask
>
>
> #define M()
> #define K()
>
> Or something.
>
> >
> > struct sys_wait {
> > @@ -93,6 +95,7 @@ static void *gem_busyspin(void *arg)
> > struct gem_busyspin *bs = arg;
> > struct drm_i915_gem_execbuffer2 execbuf;
> > struct drm_i915_gem_exec_object2 obj;
> > + const unsigned sz = bs->leak ? 16 << 20 : 4 << 10;
>
> Beause, this is quite OK still.
>
> > @@ -180,6 +188,33 @@ static void *sys_wait(void *arg)
> > return NULL;
> > }
> >
> > +static void *sys_thp_alloc(void *arg)
> > +{
> > + struct sys_wait *w = arg;
> > + struct timespec now;
> > +
> > + clock_gettime(CLOCK_MONOTONIC, &now);
> > + while (!done) {
> > + const size_t sz = 2 << 20;
> > + const struct timespec start = now;
> > + void *ptr;
> > +
> > + ptr = mmap(NULL, sz,
> > + PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS,
> > + -1, 0);
> > + assert(ptr != MAP_FAILED);
> > + madvise(ptr, sz, MADV_HUGEPAGE);
> > + for (int page = 0; page < 2 << 20 >> 12; page++)
> > + *((volatile uint32_t *)ptr + (page << 12 >> 2)) = 0;
>
> But what's the point in this iteration, we iterate from 0 to 512 page
> index (sz/PAGE_SIZE would be so much easier) and then write to to not
> each page but interleave four page writes per page and 3/4 of pages
> never get written? If this is intentional, please drop a comment.
:) As you later realised, there's an implicit <<2 from the pointer
arithmetic.
-Chris
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