[Xen-changelog] [xen-unstable] xenpaging: optimize p2m_mem_paging_populate

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1290781331 0
# Node ID 7fe9cad00e15edebe4623fc14d0ffb5165216910
# Parent  48b10f9a436e6e1cab07773df0f287a2253f6316
xenpaging: optimize p2m_mem_paging_populate

p2m_mem_paging_populate will always put another request in the ring.
To reduce pressure on the ring, place only required requests in the
ring.  If the gfn was already processed by another thread, and the
current vcpu does not need to be paused, p2m_mem_paging_resume will do
nothing with the request.  And also xenpaging will drop the request if
the vcpu does not need a wakeup.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
---
 xen/arch/x86/mm/p2m.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff -r 48b10f9a436e -r 7fe9cad00e15 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c     Fri Nov 26 14:21:33 2010 +0000
+++ b/xen/arch/x86/mm/p2m.c     Fri Nov 26 14:22:11 2010 +0000
@@ -2757,11 +2757,11 @@ void p2m_mem_paging_populate(struct p2m_
     p2m_type_t p2mt;
     struct domain *d = p2m->domain;
 
-    memset(&req, 0, sizeof(req));
-
     /* Check that there's space on the ring for this request */
     if ( mem_event_check_ring(d) )
         return;
+
+    memset(&req, 0, sizeof(req));
 
     /* Fix p2m mapping */
     /* XXX: It seems inefficient to have this here, as it's only needed
@@ -2780,6 +2780,11 @@ void p2m_mem_paging_populate(struct p2m_
     {
         vcpu_pause_nosync(v);
         req.flags |= MEM_EVENT_FLAG_VCPU_PAUSED;
+    }
+    else if ( p2mt != p2m_ram_paging_out && p2mt != p2m_ram_paged )
+    {
+        /* gfn is already on its way back and vcpu is not paused */
+        return;
     }
 
     /* Send request to pager */

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