On 03/05/2018 02:26 PM, Dave Hansen wrote:
On 02/21/2018 09:15 AM, Khalid Aziz wrote:
+tag_storage_desc_t *alloc_tag_store(struct mm_struct *mm,
+ struct vm_area_struct *vma,
+ unsigned long addr)
...
+ tags = kzalloc(size, GFP_NOWAIT|__GFP_NOWARN);
+ if (tags == NULL) {
+ tag_desc->tag_users = 0;
+ tag_desc = NULL;
+ goto out;
+ }
+ tag_desc->start = addr;
+ tag_desc->tags = tags;
+ tag_desc->end = end_addr;
+
+out:
+ spin_unlock_irqrestore(&mm->context.tag_lock, flags);
+ return tag_desc;
+}
OK, sorry, I missed this. I do see that you now have per-ADI-block tag
storage and it is not per-page.
How big can this storage get, btw? Superficially it seems like it might
be able to be gigantic for a large, sparse VMA.
Tags are stored only for the pages being swapped out, not for the pages
in entire vma. Each tag storage page can hold tags for 128 pages (each
page has 128 4-bit tags, hence 64 bytes are needed to store tags for an
entire page allowing each page to store tags for 128 pages). Sparse VMA
does not cause any problems since holes do not have corresponding pages
that will be swapped out. Tag storage pages are freed once all the pages
they store tags for have been swapped back in, except for a small number
of pages (maximum of 8) marked for emergency tag storage.
--
Khalid
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