xenpaging: use flat index for pagefile and page-in requests

This change is based on an idea by <hongkaixing@huawei.com> and
<bicky.shi@huawei.com>.

Scanning the victims[] array is time consuming with a large number of
target pages. Replace the loop to find the slot in the pagefile which
holds the requested gfn with an index.

Remove the victims array and replace it with a flat array. This array
holds the gfn for a given slot in the pagefile. Adjust all users of the
victims array.

Rename variable in main() from i to slot to clearify the meaning.

Update xenpaging_evict_page() to pass a pointer to xen_pfn_t to
xc_map_foreign_pages().

Update policy_choose_victim() to return either a gfn or INVALID_MFN.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

1 files changed, 3 insertions, 7 deletions

diff --git a/tools/xenpaging/xenpaging.h b/tools/xenpaging/xenpaging.h
index 160fc1d1c5..545f2d3626 100644
--- a/tools/xenpaging/xenpaging.h
+++ b/tools/xenpaging/xenpaging.h
@@ -46,6 +46,9 @@ struct xenpaging {
 
     unsigned long *bitmap;
 
+    unsigned long *slot_to_gfn;
+    int *gfn_to_slot;
+
     struct mem_event mem_event;
     /* number of pages for which data structures were allocated */
     int max_pages;
@@ -56,13 +59,6 @@ struct xenpaging {
     unsigned long pagein_queue[XENPAGING_PAGEIN_QUEUE_SIZE];
 };
 
-
-struct victim {
-    /* the gfn of the page to evict */
-    unsigned long gfn;
-};
-
-
 extern void create_page_in_thread(struct xenpaging *paging);
 extern void page_in_trigger(void);