Re: [Xen-devel] [PATCH 1/1] xen: move TLB-flush filtering out into populate_physmap

[Wei Liu]

On Tue, Sep 06, 2016 at 01:17:38PM +0800, Dongli Zhang wrote:
> This patch implemented parts of TODO left in commit id
> a902c12ee45fc9389eb8fe54eeddaf267a555c58. It moved TLB-flush filtering out
> into populate_physmap.
> 
> Because of TLB-flush in alloc_heap_pages, it's very slow to create a guest
> with memory size of more than 100GB on host with 100+ cpus.
> 
> This patch introduced a "MEMF_no_tlbflush" bit to memflag to indicate
> whether TLB-flush should be done in alloc_heap_pages or its caller
> populate_physmap.  Once this bit is set in memflag, alloc_heap_pages will
> ignore TLB-flush.
> 
> Signed-off-by: Dongli Zhang 
> ---
>  xen/common/memory.c | 26 ++
>  xen/common/page_alloc.c |  3 ++-
>  xen/include/xen/mm.h|  2 ++
>  3 files changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/common/memory.c b/xen/common/memory.c
> index f34dd56..14ec5fa 100644
> --- a/xen/common/memory.c
> +++ b/xen/common/memory.c
> @@ -141,6 +141,8 @@ static void populate_physmap(struct memop_args *a)
>  unsigned int i, j;
>  xen_pfn_t gpfn, mfn;
>  struct domain *d = a->domain, *curr_d = current->domain;
> + bool_t need_tlbflush = 0;
> + uint32_t tlbflush_timestamp = 0;
>  
>  if ( !guest_handle_subrange_okay(a->extent_list, a->nr_done,
>   a->nr_extents-1) )
> @@ -149,6 +151,8 @@ static void populate_physmap(struct memop_args *a)
>  if ( a->extent_order > (a->memflags & MEMF_populate_on_demand ? 
> MAX_ORDER :
>  max_order(curr_d)) )
>  return;
> + 
> + a->memflags |= MEMF_no_tlbflush;
>  
>  for ( i = a->nr_done; i < a->nr_extents; i++ )
>  {
> @@ -213,6 +217,18 @@ static void populate_physmap(struct memop_args *a)
>   i, a->nr_extents);
>  goto out;
>  }
> + 
> + for ( j = 0; j < (1U << a->extent_order); j++ )
> + {
> + if ( page[j].u.free.need_tlbflush &&
> +  (page[j].tlbflush_timestamp <= 
> tlbflush_current_time()) &&
> +  (!need_tlbflush ||
> +   (page[j].tlbflush_timestamp > 
> tlbflush_timestamp)) )
> + {
> + need_tlbflush = 1;
> + tlbflush_timestamp = 
> page[j].tlbflush_timestamp;
> + }
> + }
>  

Indentation seems rather wrong.

Please configure your editor properly.

Wei.

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[Xen-devel] [PATCH 1/1] xen: move TLB-flush filtering out into populate_physmap

[Dongli Zhang]

This patch implemented parts of TODO left in commit id
a902c12ee45fc9389eb8fe54eeddaf267a555c58. It moved TLB-flush filtering out
into populate_physmap.

Because of TLB-flush in alloc_heap_pages, it's very slow to create a guest
with memory size of more than 100GB on host with 100+ cpus.

This patch introduced a "MEMF_no_tlbflush" bit to memflag to indicate
whether TLB-flush should be done in alloc_heap_pages or its caller
populate_physmap.  Once this bit is set in memflag, alloc_heap_pages will
ignore TLB-flush.

Signed-off-by: Dongli Zhang 
---
 xen/common/memory.c | 26 ++
 xen/common/page_alloc.c |  3 ++-
 xen/include/xen/mm.h|  2 ++
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index f34dd56..14ec5fa 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -141,6 +141,8 @@ static void populate_physmap(struct memop_args *a)
 unsigned int i, j;
 xen_pfn_t gpfn, mfn;
 struct domain *d = a->domain, *curr_d = current->domain;
+   bool_t need_tlbflush = 0;
+   uint32_t tlbflush_timestamp = 0;
 
 if ( !guest_handle_subrange_okay(a->extent_list, a->nr_done,
  a->nr_extents-1) )
@@ -149,6 +151,8 @@ static void populate_physmap(struct memop_args *a)
 if ( a->extent_order > (a->memflags & MEMF_populate_on_demand ? MAX_ORDER :
 max_order(curr_d)) )
 return;
+   
+   a->memflags |= MEMF_no_tlbflush;
 
 for ( i = a->nr_done; i < a->nr_extents; i++ )
 {
@@ -213,6 +217,18 @@ static void populate_physmap(struct memop_args *a)
  i, a->nr_extents);
 goto out;
 }
+   
+   for ( j = 0; j < (1U << a->extent_order); j++ )
+   {
+   if ( page[j].u.free.need_tlbflush &&
+(page[j].tlbflush_timestamp <= 
tlbflush_current_time()) &&
+(!need_tlbflush ||
+ (page[j].tlbflush_timestamp > 
tlbflush_timestamp)) )
+   {
+   need_tlbflush = 1;
+   tlbflush_timestamp = 
page[j].tlbflush_timestamp;
+   }
+   }
 
 mfn = page_to_mfn(page);
 }
@@ -232,6 +248,16 @@ static void populate_physmap(struct memop_args *a)
 }
 
 out:
+   if ( need_tlbflush )
+   {
+   cpumask_t mask = cpu_online_map;
+   tlbflush_filter(mask, tlbflush_timestamp);
+   if ( !cpumask_empty() )
+   {
+   perfc_incr(need_flush_tlb_flush);
+   flush_tlb_mask();
+   }
+   }
 a->nr_done = i;
 }
 
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 18ff6cf..79f633b 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -827,7 +827,8 @@ static struct page_info *alloc_heap_pages(
 BUG_ON(pg[i].count_info != PGC_state_free);
 pg[i].count_info = PGC_state_inuse;
 
-if ( pg[i].u.free.need_tlbflush &&
+if ( !(memflags & MEMF_no_tlbflush) &&
+pg[i].u.free.need_tlbflush &&
  (pg[i].tlbflush_timestamp <= tlbflush_current_time()) &&
  (!need_tlbflush ||
   (pg[i].tlbflush_timestamp > tlbflush_timestamp)) )
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 58bc0b8..880ca88 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -221,6 +221,8 @@ struct npfec {
 #define  MEMF_exact_node  (1U<<_MEMF_exact_node)
 #define _MEMF_no_owner5
 #define  MEMF_no_owner(1U<<_MEMF_no_owner)
+#define _MEMF_no_tlbflush 6
+#define  MEMF_no_tlbflush (1U<<_MEMF_no_tlbflush)
 #define _MEMF_node8
 #define  MEMF_node_mask   ((1U << (8 * sizeof(nodeid_t))) - 1)
 #define  MEMF_node(n) n) + 1) & MEMF_node_mask) << _MEMF_node)
-- 
1.9.1


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