From 5a6a7ae5e6d79a72dc6b0b94f39441e64f664193 Mon Sep 17 00:00:00 2001 From: George Dunlap Date: Thu, 28 Jun 2012 15:18:03 +0100 Subject: [PATCH] xen,pod: Zero-check recently populated pages (checklast) When demand-populating pages due to guest accesses, check recently populated pages to see if we can reclaim them for the cache. This should keep the PoD cache filled when the start-of-day scrubber is going through. The number 128 was chosen by experiment. Windows does its page scrubbing in parallel; while a small nubmer like 4 works well for single VMs, it breaks down as multiple vcpus are scrubbing different pages in parallel. Increasing to 128 works well for higher numbers of vcpus. v2: - Wrapped some long lines - unsigned int for index, unsigned long for array v3: - Use PAGE_ORDER_2M instead of 9 - Removed inappropriate use of p2m_pod_zero_check_superpage() return value Signed-off-by: George Dunlap Acked-by: Tim Deegan Committed-by: Tim Deegan --- xen/arch/x86/mm/p2m-pod.c | 27 +++++++++++++++++++++++++++ xen/include/asm-x86/p2m.h | 4 ++++ 2 files changed, 31 insertions(+) diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c index dbdf966645..ed62f1e870 100644 --- a/xen/arch/x86/mm/p2m-pod.c +++ b/xen/arch/x86/mm/p2m-pod.c @@ -926,6 +926,27 @@ p2m_pod_emergency_sweep_super(struct p2m_domain *p2m) p2m->pod.reclaim_super = i ? i - SUPERPAGE_PAGES : 0; } +/* When populating a new superpage, look at recently populated superpages + * hoping that they've been zeroed. This will snap up zeroed pages as soon as + * the guest OS is done with them. */ +static void +p2m_pod_check_last_super(struct p2m_domain *p2m, unsigned long gfn_aligned) +{ + unsigned long check_gfn; + + ASSERT(p2m->pod.last_populated_index < POD_HISTORY_MAX); + + check_gfn = p2m->pod.last_populated[p2m->pod.last_populated_index]; + + p2m->pod.last_populated[p2m->pod.last_populated_index] = gfn_aligned; + + p2m->pod.last_populated_index = + ( p2m->pod.last_populated_index + 1 ) % POD_HISTORY_MAX; + + p2m_pod_zero_check_superpage(p2m, check_gfn); +} + + #define POD_SWEEP_STRIDE 16 static void p2m_pod_emergency_sweep(struct p2m_domain *p2m) @@ -1083,6 +1104,12 @@ p2m_pod_demand_populate(struct p2m_domain *p2m, unsigned long gfn, __trace_var(TRC_MEM_POD_POPULATE, 0, sizeof(t), &t); } + /* Check the last guest demand-populate */ + if ( p2m->pod.entry_count > p2m->pod.count + && (order == PAGE_ORDER_2M) + && (q & P2M_ALLOC) ) + p2m_pod_check_last_super(p2m, gfn_aligned); + pod_unlock(p2m); return 0; out_of_memory: diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h index 63bc7cf451..dc5c9b81eb 100644 --- a/xen/include/asm-x86/p2m.h +++ b/xen/include/asm-x86/p2m.h @@ -287,6 +287,10 @@ struct p2m_domain { unsigned reclaim_super; /* Last gpfn of a scan */ unsigned reclaim_single; /* Last gpfn of a scan */ unsigned max_guest; /* gpfn of max guest demand-populate */ +#define POD_HISTORY_MAX 128 + /* gpfn of last guest superpage demand-populated */ + unsigned long last_populated[POD_HISTORY_MAX]; + unsigned int last_populated_index; mm_lock_t lock; /* Locking of private pod structs, * * not relying on the p2m lock. */ } pod; -- 2.30.2