Reduce impact of saving/restoring/dumping large domains on Dom0 memory

usage by means of fadvise64() to tell the OS to discard the cache
pages used for the save/dump file.

Signed-off-by: Simon Graham <Simon.Graham@stratus.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/tools/libxc/xc_core.c b/tools/libxc/xc_core.c
index 7ea97cd6d0..31c1532b69 100644
--- a/tools/libxc/xc_core.c
+++ b/tools/libxc/xc_core.c
@@ -802,6 +802,12 @@ static int local_file_dump(void *args, char *buffer, unsigned int length)
         }
     }
 
+    if (length >= DUMP_INCREMENT*PAGE_SIZE) {
+        // Now dumping pages -- make sure we discard clean pages from
+        // the cache after each write
+        discard_file_cache(da->fd, 0 /* no flush */);
+    }
+
     return 0;
 }
 
@@ -822,6 +828,9 @@ xc_domain_dumpcore(int xc_handle,
     sts = xc_domain_dumpcore_via_callback(
         xc_handle, domid, &da, &local_file_dump);
 
+    /* flush and discard any remaining portion of the file from cache */
+    discard_file_cache(da.fd, 1/* flush first*/);
+
     close(da.fd);
 
     return sts;