From 4443856dbcb52065658f287cbf6dd17bc5d527d0 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Mon, 30 Jul 2012 10:18:05 -0400 Subject: [PATCH] xen/p2m: Reserve 8MB of _brk space for P2M leafs when populating back. When we release pages back during bootup: Freeing 9d-100 pfn range: 99 pages freed Freeing 9cf36-9d0d2 pfn range: 412 pages freed Freeing 9f6bd-9f6bf pfn range: 2 pages freed Freeing 9f714-9f7bf pfn range: 171 pages freed Freeing 9f7e0-9f7ff pfn range: 31 pages freed Freeing 9f800-100000 pfn range: 395264 pages freed Released 395979 pages of unused memory We then try to populate those pages back. In the P2M tree however the space for those leafs must be reserved - as such we use extend_brk. We reserve 8MB of _brk space, which means we can fit over 1048576 PFNs - which is more than we should ever need. [v1: Made it 8MB of _brk space instead of 4MB per Jan's suggestion] Signed-off-by: Konrad Rzeszutek Wilk (cherry picked from commit 99266871de5006ba7ad0bfece6bb283ede4094b9) --- arch/x86/xen/p2m.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c index ff98308d24cf..f95a0debadbd 100644 --- a/arch/x86/xen/p2m.c +++ b/arch/x86/xen/p2m.c @@ -194,6 +194,11 @@ RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID * boundary violation will require three middle nodes. */ RESERVE_BRK(p2m_mid_identity, PAGE_SIZE * 2 * 3); +/* When we populate back during bootup, the amount of pages can vary. The + * max we have is seen is 395979, but that does not mean it can't be more. + * But some machines can have 3GB I/O holes even. So lets reserve enough + * for 4GB of I/O and E820 holes. */ +RESERVE_BRK(p2m_populated, PMD_SIZE * 4); static inline unsigned p2m_top_index(unsigned long pfn) { BUG_ON(pfn >= MAX_P2M_PFN); -- 2.50.1