Tim Deegan
2010-Oct-21 15:19 UTC
[Xen-devel] [PATCH] Allow max_pages to be set to less than tot_pages
The memory allocation code sometimes needs to enforce that a guest
that''s been told to balloon down isn''t going to expand further
(because
it''s still executing a previous balloon-up operation). That means
being
able to set the desired max_pages even before the balloon driver has
brought tot_pages down to the right level.
Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
diff -r 95226c6fe89b xen/common/domctl.c
--- a/xen/common/domctl.c Mon Jun 01 11:31:38 2009 +0100
+++ b/xen/common/domctl.c Mon Jun 01 15:41:41 2009 +0100
@@ -675,11 +675,11 @@
new_max = op->u.max_mem.max_memkb >> (PAGE_SHIFT-10);
spin_lock(&d->page_alloc_lock);
- if ( new_max >= d->tot_pages )
- {
- d->max_pages = new_max;
- ret = 0;
- }
+ /* N.B. We removed a check that new_max >= current tot_pages;
+ * this means the domain will "ratchet" down to new_max.
+ * In the meantime tot will be > max. */
+ d->max_pages = new_max;
+ ret = 0;
spin_unlock(&d->page_alloc_lock);
max_mem_out:
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Ian Jackson
2010-Oct-21 17:26 UTC
Re: [Xen-devel] [PATCH] Allow max_pages to be set to less than tot_pages
Tim Deegan writes ("[Xen-devel] [PATCH] Allow max_pages to be set to less
than tot_pages"):> The memory allocation code sometimes needs to enforce that a guest
> that''s been told to balloon down isn''t going to expand
further (because
> it''s still executing a previous balloon-up operation). That means
being
> able to set the desired max_pages even before the balloon driver has
> brought tot_pages down to the right level.
>
> Signed-off-by: Tim Deegan <Tim.Deegan@citrix.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Ian.
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