On 01/04/2017 03:40 PM, Dave Hansen wrote:
On 01/04/2017 03:35 PM, Rob Gardner wrote:
Tags are not cleared at all when memory is freed, but rather, lazily
(and automatically) cleared when memory is allocated.
What does "allocated" mean in this context? Physical or virtual? What
does this do, for instance?
The first time a virtual page is touched by a process after the malloc,
the kernel does clear_user_page() or something similar, which zeroes the
memory. At the same time, the memory tags are cleared.
Rob
ptr = malloc(PAGE_SIZE);
set_tag(ptr, 14);
madvise(ptr, PAGE_SIZE, MADV_FREE);
printf("tag: %d\n", get_tag(ptr));
free(ptr);
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