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Commit 80c5e73d authored by Venki Pallipadi's avatar Venki Pallipadi Committed by Ingo Molnar
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x86: fix Xorg startup/shutdown slowdown with PAT 



Rene Herman reported significant Xorg startup/shutdown slowdown due
to PAT. It turns out that the memtype list has thousands of entries.

Add cached_entry to list add routine, in order to speed up the
lookup for sequential reserve_memtype calls.

Reported-by: default avatarRene Herman <rene.herman@keyaccess.nl>
Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c6744955

arch/x86/mm/pat.c

+31 −2
Original line number Diff line number Diff line
@@ -207,6 +207,9 @@ static int chk_conflict(struct memtype *new, struct memtype *entry, 
	return -EBUSY;

}



static struct memtype *cached_entry;

static u64 cached_start;



/*

 * req_type typically has one of the:

 * - _PAGE_CACHE_WB
@@ -280,11 +283,17 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type, 


	spin_lock(&memtype_lock);



	if (cached_entry && start >= cached_start)

		entry = cached_entry;

	else

		entry = list_entry(&memtype_list, struct memtype, nd);



	/* Search for existing mapping that overlaps the current range */

	where = NULL;

	list_for_each_entry(entry, &memtype_list, nd) {

	list_for_each_entry_continue(entry, &memtype_list, nd) {

		if (end <= entry->start) {

			where = entry->nd.prev;

			cached_entry = list_entry(where, struct memtype, nd);

			break;

		} else if (start <= entry->start) { /* end > entry->start */

			err = chk_conflict(new, entry, new_type);
@@ -292,6 +301,8 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type, 
				dprintk("Overlap at 0x%Lx-0x%Lx\n",

					entry->start, entry->end);

				where = entry->nd.prev;

				cached_entry = list_entry(where,

							struct memtype, nd);

			}

			break;

		} else if (start < entry->end) { /* start > entry->start */
@@ -299,7 +310,20 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type, 
			if (!err) {

				dprintk("Overlap at 0x%Lx-0x%Lx\n",

					entry->start, entry->end);

				where = &entry->nd;

				cached_entry = list_entry(entry->nd.prev,

							struct memtype, nd);



				/*

				 * Move to right position in the linked

				 * list to add this new entry

				 */

				list_for_each_entry_continue(entry,

							&memtype_list, nd) {

					if (start <= entry->start) {

						where = entry->nd.prev;

						break;

					}

				}

			}

			break;

		}
@@ -314,6 +338,8 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type, 
		return err;

	}



	cached_start = start;



	if (where)

		list_add(&new->nd, where);

	else
@@ -343,6 +369,9 @@ int free_memtype(u64 start, u64 end) 
	spin_lock(&memtype_lock);

	list_for_each_entry(entry, &memtype_list, nd) {

		if (entry->start == start && entry->end == end) {

			if (cached_entry == entry || cached_start == start)

				cached_entry = NULL;



			list_del(&entry->nd);

			kfree(entry);

			err = 0;