On Fri, 21 Apr 2023, Reinette Chatre wrote:
> On 4/18/2023 4:44 AM, Ilpo Järvinen wrote:
> >
> > diff --git a/tools/testing/selftests/resctrl/fill_buf.c b/tools/testing/selftests/resctrl/fill_buf.c
> > index 5cdb421a2f6c..6f0438aa71a6 100644
> > --- a/tools/testing/selftests/resctrl/fill_buf.c
> > +++ b/tools/testing/selftests/resctrl/fill_buf.c
> > @@ -24,6 +24,11 @@
> >
> > static unsigned char *startptr;
> >
> > +void free_buffer(void)
> > +{
> > + free(startptr);
> > +}
> > +
>
> >From what I understand startptr is a global variable because there used
> to be a signal handler that attempted to free the buffer as part of
> its cleanup. This was not necessary and this behavior no longer exists,
> yet the global buffer pointer remains.
> See commit 73c55fa5ab55 ("selftests/resctrl: Commonize the signal handler
> register/unregister for all tests")
>
> I do not see why a global buffer pointer with all these indirections
> are needed. Why not just use a local pointer and pass it to functions
> as needed? In the above case, just call free(pointer) directly from the
> test.
OK, I'll try to convert all this into using non-global pointers then. It
requires a bit refactoring but, IIRC, it is doable.
> > static void sb(void)
> > {
> > #if defined(__i386) || defined(__x86_64)
> > @@ -138,36 +143,53 @@ static int fill_cache_write(unsigned char *start_ptr, unsigned char *end_ptr,
> > return 0;
> > }
> >
> > -static int
> > -fill_cache(unsigned long long buf_size, int memflush, int op, char *resctrl_val)
> > +int alloc_buffer(unsigned long long buf_size, int memflush)
> > {
>
> This can be an allocation function that returns a pointer to
> allocated buffer, NULL if error.
>
> > - unsigned char *start_ptr, *end_ptr;
> > - int ret;
> > + unsigned char *start_ptr;
> >
> > start_ptr = malloc_and_init_memory(buf_size);
> > if (!start_ptr)
> > return -1;
> >
> > startptr = start_ptr;
> > - end_ptr = start_ptr + buf_size;
> >
> > /* Flush the memory before using to avoid "cache hot pages" effect */
> > if (memflush)
> > mem_flush(start_ptr, buf_size);
> >
> > + return 0;
> > +}
> > +
> > +int use_buffer(unsigned long long buf_size, int op, char *resctrl_val)
> > +{
> > + unsigned char *end_ptr;
> > + int ret;
> > +
> > + end_ptr = startptr + buf_size;
> > if (op == 0)
> > - ret = fill_cache_read(start_ptr, end_ptr, resctrl_val);
> > + ret = fill_cache_read(startptr, end_ptr, resctrl_val);
> > else
> > - ret = fill_cache_write(start_ptr, end_ptr, resctrl_val);
> > + ret = fill_cache_write(startptr, end_ptr, resctrl_val);
> >
> > - if (ret) {
> > + if (ret)
> > printf("\n Error in fill cache read/write...\n");
> > - return -1;
> > - }
> >
> > - free(startptr);
> > + return ret;
> > +}
> >
>
> This seems like an unnecessary level of abstraction to me. Could
> callers not just call fill_cache_read()/fill_cache_write() directly?
> I think doing so will make tests easier to understand. Looking ahead
> at how cat_val() turns out in the final patch I do think a call
> to fill_cache_read() is easier to follow than this abstraction.
Passing a custom benchmark command with -b would lose some functionality
if this abstraction is removed. CAT test could make a direct call though
as it doesn't care about the benchmark command.
How useful that -b functionality is for selftesting is somewhat
questionable though.
--
i.
