[Xen-devel] [PATCH 11 of 24] xenpaging: retry unpageable gfns

[Olaf Hering <olaf@xxxxxxxxx>]

# HG changeset patch
# User Olaf Hering <olaf@xxxxxxxxx>
# Date 1317653608 -7200
# Node ID 3924c1ef71ee975b4556ca7766b730dfa3e12295
# Parent  b85b2fa9a485cdd815eb9eb3e3a7794b462fa814
xenpaging: retry unpageable gfns

Nomination of gfns can fail, but may succeed later.
Thats the case for a guest that starts ballooned.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

diff -r b85b2fa9a485 -r 3924c1ef71ee tools/xenpaging/policy_default.c
--- a/tools/xenpaging/policy_default.c
+++ b/tools/xenpaging/policy_default.c
@@ -32,6 +32,7 @@ static unsigned int i_mru;
 static unsigned int mru_size;
 static unsigned long *bitmap;
 static unsigned long *unconsumed;
+static unsigned int unconsumed_cleared;
 static unsigned long current_gfn;
 static unsigned long max_pages;
 
@@ -87,8 +88,20 @@ int policy_choose_victim(xenpaging_t *pa
         current_gfn++;
         if ( current_gfn >= max_pages )
             current_gfn = 0;
+        /* Could not nominate any gfn */
         if ( wrap == current_gfn )
         {
+            /* Count wrap arounds */
+            unconsumed_cleared++;
+            /* Force retry every few seconds (depends on poll() timeout) */
+            if ( unconsumed_cleared > 123)
+            {
+                /* Force retry of unconsumed gfns */
+                bitmap_clear(unconsumed, max_pages);
+                unconsumed_cleared = 0;
+                /* One more round before returning ENOSPC */
+                continue;
+            }
             victim->gfn = INVALID_MFN;
             return -ENOSPC;
         }

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