Re: [PATCH 3/3] test: slab_arena -- Verify madvise

[Vladimir Davydov <vdavydov.dev@gmail.com>]

[Cc += Alexander re tests]

On Wed, May 01, 2019 at 06:50:06PM +0300, Cyrill Gorcunov wrote:
> Since madvise support depends on sys libraries
> and kernel version we print error if only small
> supports it and /proc/self/smaps provide more
> less decent VmFlags.

TBO I wouldn't bother testing this feature at all, because it's way too
platform dependent.

Alternatively, we could test it by crashing a process and checking the
size of the generated core file, but then again it doesn't look like a
portable way.

Alexander, any ideas?

> 
> Part of #3509
> ---
> https://github.com/tarantool/tarantool/issues/3509
> 
>  test/slab_arena.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 90 insertions(+)
> 
> diff --git a/test/slab_arena.c b/test/slab_arena.c
> index d0a78d1..5c5085c 100644
> --- a/test/slab_arena.c
> +++ b/test/slab_arena.c
> @@ -3,6 +3,7 @@
>  #include <stdio.h>
>  #include <limits.h>
>  #include <stdlib.h>
> +#include <string.h>
>  #include <time.h>
>  #include "unit.h"
>  
> @@ -15,6 +16,93 @@ slab_arena_print(struct slab_arena *arena)
>  	       arena->used, arena->slab_size);
>  }
>  
> +#define is_hex_digit(c)				\
> +	(((c) >= '0' && (c) <= '9')	||	\
> +	 ((c) >= 'a' && (c) <= 'f')	||	\
> +	 ((c) >= 'A' && (c) <= 'F'))
> +
> +static int is_vma_range_fmt(char *line, unsigned long *start, unsigned long *end)
> +{
> +	char *p = line;
> +	while (*line && is_hex_digit(*line))
> +		line++;
> +
> +	if (*line++ != '-')
> +		return 0;
> +
> +	while (*line && is_hex_digit(*line))
> +		line++;
> +
> +	if (*line++ != ' ')
> +		return 0;
> +
> +	sscanf(p, "%lx-%lx", start, end);
> +	return 1;
> +}
> +
> +static void
> +slab_test_madvise(void)
> +{
> +	struct slab_arena arena;
> +	struct quota quota;
> +	FILE *f = NULL;
> +	void *ptr;
> +
> +	quota_init(&quota, 2000000);
> +	slab_arena_create(&arena, &quota, 3000000, 1, MAP_PRIVATE);
> +
> +	/*
> +	 * Will fetch from preallocated area.
> +	 */
> +	ptr = slab_map(&arena);
> +	if (!ptr) {
> +		printf("can't obtain slab\n");
> +		goto out;
> +	}
> +
> +	/*
> +	 * If system supports madvise call, we should try
> +	 * fetch the precise VMA state from smaps file,
> +	 * but if only it exists.
> +	 */
> +	if (!slab_arena_madvise_dontdump(&arena)) {
> +		unsigned long start = 0, end = 0;
> +		char buf[1024], *tok = NULL;
> +		bool found = false;
> +
> +		f = fopen("/proc/self/smaps", "r");
> +		if (!f)
> +			goto out;
> +
> +		while (fgets(buf, sizeof(buf), f)) {
> +			is_vma_range_fmt(buf, &start, &end);
> +			if (strncmp(buf, "VmFlags: ", 9) || (void *)start != ptr)
> +				continue;
> +			tok = buf;
> +			break;
> +		}
> +
> +		if (tok) {
> +			for (tok = strtok(tok, " \n"); tok;
> +			     tok = strtok(NULL, " \n")) {
> +				if (strcmp(tok, "dd"))
> +					continue;
> +				found = true;
> +				break;
> +			}
> +		}
> +
> +		if (!found)
> +			printf("ERROR: Expected dd flag on VMA address %p\n", ptr);
> +
> +		fclose(f);
> +	}
> +
> +out:
> +	slab_unmap(&arena, ptr);
> +	slab_arena_destroy(&arena);
> +}
> +
>  int main()
>  {
>  	struct quota quota;
> @@ -42,4 +130,6 @@ int main()
>  	slab_arena_create(&arena, &quota, 3000000, 1, MAP_PRIVATE);
>  	slab_arena_print(&arena);
>  	slab_arena_destroy(&arena);
> +
> +	slab_test_madvise();
>  }