* Nai Xia (nai.xia@xxxxxxxxx) wrote:
> Introduced ksm_page_changed() to reference the dirty bit of a pte. We clear
> the dirty bit for each pte scanned but don't flush the tlb. For a huge page,
> if one of the subpage has changed, we try to skip the whole huge page
> assuming(this is true by now) that ksmd linearly scans the address space.
This doesn't build w/ kvm as a module.
> A NEW_FLAG is also introduced as a status of rmap_item to make ksmd scan
> more aggressively for new VMAs - only skip the pages considered to be volatile
> by the dirty bits. This can be enabled/disabled through KSM's sysfs interface.
This seems like it should be separated out. And while it might be useful
to enable/disable for testing, I don't think it's worth supporting for
the long term. Would also be useful to see the value of this flag.
> @@ -454,7 +468,7 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node)
> else
> ksm_pages_shared--;
> put_anon_vma(rmap_item->anon_vma);
> - rmap_item->address &= PAGE_MASK;
> + rmap_item->address &= ~STABLE_FLAG;
> cond_resched();
> }
>
> @@ -542,7 +556,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
> ksm_pages_shared--;
>
> put_anon_vma(rmap_item->anon_vma);
> - rmap_item->address &= PAGE_MASK;
> + rmap_item->address &= ~STABLE_FLAG;
>
> } else if (rmap_item->address & UNSTABLE_FLAG) {
> unsigned char age;
> @@ -554,12 +568,14 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
> * than left over from before.
> */
> age = (unsigned char)(ksm_scan.seqnr - rmap_item->address);
> - BUG_ON(age > 1);
> + BUG_ON (age > 1);
No need to add space after BUG_ON() there
> +
> if (!age)
> rb_erase(&rmap_item->node, &root_unstable_tree);
>
> ksm_pages_unshared--;
> - rmap_item->address &= PAGE_MASK;
> + rmap_item->address &= ~UNSTABLE_FLAG;
> + rmap_item->address &= ~SEQNR_MASK;
None of these changes are needed AFAICT. &= PAGE_MASK clears all
relevant bits. How could it be in a tree, have NEW_FLAG set, and
while removing from tree want to preserve NEW_FLAG?
thanks,
-chris
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