lkml.org 
[lkml]   [2012]   [Dec]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH v2 04/10] kvm: Minor memory slot optimization
From
Date
If a slot is removed or moved in the guest physical address space, we
first allocate and install a new slot array with the invalidated
entry. The old array is then freed. We then proceed to allocate yet
another slot array to install the permanent replacement. Re-use the
original array when this occurs and avoid the extra kfree/kmalloc.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
virt/kvm/kvm_main.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0f66a0e..2a80dac 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -711,7 +711,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
unsigned long npages;
struct kvm_memory_slot *memslot, *slot;
struct kvm_memory_slot old, new;
- struct kvm_memslots *slots, *old_memslots;
+ struct kvm_memslots *slots = NULL, *old_memslots;

r = check_memory_region_flags(mem);
if (r)
@@ -827,18 +827,25 @@ int __kvm_set_memory_region(struct kvm *kvm,
* - kvm_is_visible_gfn (mmu_check_roots)
*/
kvm_arch_flush_shadow_memslot(kvm, slot);
- kfree(old_memslots);
+ slots = old_memslots;
}

r = kvm_arch_prepare_memory_region(kvm, &new, old, mem, user_alloc);
if (r)
- goto out_free;
+ goto out_slots;

r = -ENOMEM;
- slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots),
- GFP_KERNEL);
- if (!slots)
- goto out_free;
+ /*
+ * We can re-use the old_memslots from above, the only difference
+ * from the currently installed memslots is the invalid flag. This
+ * will get overwritten by update_memslots anyway.
+ */
+ if (!slots) {
+ slots = kmemdup(kvm->memslots, sizeof(struct kvm_memslots),
+ GFP_KERNEL);
+ if (!slots)
+ goto out_free;
+ }

/* map new memory slot into the iommu */
if (npages) {


\
 
 \ /
  Last update: 2012-12-10 19:01    [W:0.072 / U:4.420 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site