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Subject: Re: [RFC PATCH v3] sparc64: Add support for Application Data
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From: Rob Gardner <rob.gardner@oracle.com>
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Date: Wed, 4 Jan 2017 15:44:56 -0800
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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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