# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1213290840 -3600
# Node ID 09dd5999401b69ee1561d68747874995a2231908
# Parent 98ed32885ec029f7d5dd1646b1469e6c15296421
x86: remove use of per-domain lock from page table entry handling
This change results in a 5% performance improvement for kernel builds
on dual-socket quad-core systems (which is what I used for reference
for both 32- and 64-bit). Along with that, the amount of time reported
as spent in the kernel gets reduced by almost 25% (the fraction of
time spent in the kernel is generally reported significantly higher
under Xen than with a native kernel).
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
xen/arch/x86/domain.c | 2
xen/arch/x86/domain_build.c | 1
xen/arch/x86/mm.c | 189 ++++++++++++++++++++++++++++++--------------
xen/include/asm-x86/mm.h | 8 -
4 files changed, 136 insertions(+), 64 deletions(-)
diff -r 98ed32885ec0 -r 09dd5999401b xen/arch/x86/domain.c
--- a/xen/arch/x86/domain.c Thu Jun 12 17:57:03 2008 +0100
+++ b/xen/arch/x86/domain.c Thu Jun 12 18:14:00 2008 +0100
@@ -174,7 +174,7 @@ static int setup_compat_l4(struct vcpu *
return -ENOMEM;
/* This page needs to look like a pagetable so that it can be shadowed */
- pg->u.inuse.type_info = PGT_l4_page_table|PGT_validated;
+ pg->u.inuse.type_info = PGT_l4_page_table|PGT_validated|1;
l4tab = copy_page(page_to_virt(pg), idle_pg_table);
l4tab[0] = l4e_empty();
diff -r 98ed32885ec0 -r 09dd5999401b xen/arch/x86/domain_build.c
--- a/xen/arch/x86/domain_build.c Thu Jun 12 17:57:03 2008 +0100
+++ b/xen/arch/x86/domain_build.c Thu Jun 12 18:14:00 2008 +0100
@@ -575,6 +575,7 @@ int __init construct_dom0(
page = alloc_domheap_page(NULL, 0);
if ( !page )
panic("Not enough RAM for domain 0 PML4.\n");
+ page->u.inuse.type_info = PGT_l4_page_table|PGT_validated|1;
l4start = l4tab = page_to_virt(page);
}
copy_page(l4tab, idle_pg_table);
diff -r 98ed32885ec0 -r 09dd5999401b xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Thu Jun 12 17:57:03 2008 +0100
+++ b/xen/arch/x86/mm.c Thu Jun 12 18:14:00 2008 +0100
@@ -201,6 +201,11 @@ void __init init_frametable(void)
}
memset(frame_table, 0, nr_pages << PAGE_SHIFT);
+
+#if defined(__x86_64__)
+ for ( i = 0; i < max_page; i ++ )
+ spin_lock_init(&frame_table[i].lock);
+#endif
}
void __init arch_init_memory(void)
@@ -1356,6 +1361,25 @@ static void free_l4_table(struct page_in
#endif
+static void page_lock(struct page_info *page)
+{
+#if defined(__i386__)
+ while ( unlikely(test_and_set_bit(_PGC_locked, &page->count_info)) )
+ while ( test_bit(_PGC_locked, &page->count_info) )
+ cpu_relax();
+#else
+ spin_lock(&page->lock);
+#endif
+}
+
+static void page_unlock(struct page_info *page)
+{
+#if defined(__i386__)
+ clear_bit(_PGC_locked, &page->count_info);
+#else
+ spin_unlock(&page->lock);
+#endif
+}
/* How to write an entry to the guest pagetables.
* Returns 0 for failure (pointer not valid), 1 for success. */
@@ -1417,24 +1441,33 @@ static int mod_l1_entry(l1_pgentry_t *pl
struct vcpu *curr = current;
struct domain *d = curr->domain;
unsigned long mfn;
+ struct page_info *l1pg = mfn_to_page(gl1mfn);
+ int rc = 1;
+
+ page_lock(l1pg);
if ( unlikely(__copy_from_user(&ol1e, pl1e, sizeof(ol1e)) != 0) )
- return 0;
+ return page_unlock(l1pg), 0;
if ( unlikely(paging_mode_refcounts(d)) )
- return UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr, preserve_ad);
+ {
+ rc = UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr, preserve_ad);
+ page_unlock(l1pg);
+ return rc;
+ }
if ( l1e_get_flags(nl1e) & _PAGE_PRESENT )
{
/* Translate foreign guest addresses. */
mfn = gmfn_to_mfn(FOREIGNDOM, l1e_get_pfn(nl1e));
if ( unlikely(mfn == INVALID_MFN) )
- return 0;
+ return page_unlock(l1pg), 0;
ASSERT((mfn & ~(PADDR_MASK >> PAGE_SHIFT)) == 0);
nl1e = l1e_from_pfn(mfn, l1e_get_flags(nl1e));
if ( unlikely(l1e_get_flags(nl1e) & l1_disallow_mask(d)) )
{
+ page_unlock(l1pg);
MEM_LOG("Bad L1 flags %x",
l1e_get_flags(nl1e) & l1_disallow_mask(d));
return 0;
@@ -1444,30 +1477,33 @@ static int mod_l1_entry(l1_pgentry_t *pl
if ( !l1e_has_changed(ol1e, nl1e, _PAGE_RW | _PAGE_PRESENT) )
{
adjust_guest_l1e(nl1e, d);
- return UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr,
- preserve_ad);
+ rc = UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr,
+ preserve_ad);
+ page_unlock(l1pg);
+ return rc;
}
if ( unlikely(!get_page_from_l1e(nl1e, FOREIGNDOM)) )
- return 0;
+ return page_unlock(l1pg), 0;
adjust_guest_l1e(nl1e, d);
if ( unlikely(!UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr,
preserve_ad)) )
{
- put_page_from_l1e(nl1e, d);
- return 0;
- }
- }
- else
- {
- if ( unlikely(!UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr,
- preserve_ad)) )
- return 0;
- }
-
+ ol1e = nl1e;
+ rc = 0;
+ }
+ }
+ else if ( unlikely(!UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, curr,
+ preserve_ad)) )
+ {
+ page_unlock(l1pg);
+ return 0;
+ }
+
+ page_unlock(l1pg);
put_page_from_l1e(ol1e, d);
- return 1;
+ return rc;
}
@@ -1481,6 +1517,8 @@ static int mod_l2_entry(l2_pgentry_t *pl
l2_pgentry_t ol2e;
struct vcpu *curr = current;
struct domain *d = curr->domain;
+ struct page_info *l2pg = mfn_to_page(pfn);
+ int rc = 1;
if ( unlikely(!is_guest_l2_slot(d, type, pgentry_ptr_to_slot(pl2e))) )
{
@@ -1488,13 +1526,16 @@ static int mod_l2_entry(l2_pgentry_t *pl
return 0;
}
+ page_lock(l2pg);
+
if ( unlikely(__copy_from_user(&ol2e, pl2e, sizeof(ol2e)) != 0) )
- return 0;
+ return page_unlock(l2pg), 0;
if ( l2e_get_flags(nl2e) & _PAGE_PRESENT )
{
if ( unlikely(l2e_get_flags(nl2e) & L2_DISALLOW_MASK) )
{
+ page_unlock(l2pg);
MEM_LOG("Bad L2 flags %x",
l2e_get_flags(nl2e) & L2_DISALLOW_MASK);
return 0;
@@ -1504,28 +1545,32 @@ static int mod_l2_entry(l2_pgentry_t *pl
if ( !l2e_has_changed(ol2e, nl2e, _PAGE_PRESENT) )
{
adjust_guest_l2e(nl2e, d);
- return UPDATE_ENTRY(l2, pl2e, ol2e, nl2e, pfn, curr, preserve_ad);
+ rc = UPDATE_ENTRY(l2, pl2e, ol2e, nl2e, pfn, curr, preserve_ad);
+ page_unlock(l2pg);
+ return rc;
}
if ( unlikely(!get_page_from_l2e(nl2e, pfn, d)) )
- return 0;
+ return page_unlock(l2pg), 0;
adjust_guest_l2e(nl2e, d);
if ( unlikely(!UPDATE_ENTRY(l2, pl2e, ol2e, nl2e, pfn, curr,
preserve_ad)) )
{
- put_page_from_l2e(nl2e, pfn);
- return 0;
+ ol2e = nl2e;
+ rc = 0;
}
}
else if ( unlikely(!UPDATE_ENTRY(l2, pl2e, ol2e, nl2e, pfn, curr,
preserve_ad)) )
{
+ page_unlock(l2pg);
return 0;
}
+ page_unlock(l2pg);
put_page_from_l2e(ol2e, pfn);
- return 1;
+ return rc;
}
#if CONFIG_PAGING_LEVELS >= 3
@@ -1539,7 +1584,8 @@ static int mod_l3_entry(l3_pgentry_t *pl
l3_pgentry_t ol3e;
struct vcpu *curr = current;
struct domain *d = curr->domain;
- int okay;
+ struct page_info *l3pg = mfn_to_page(pfn);
+ int okay, rc = 1;
if ( unlikely(!is_guest_l3_slot(pgentry_ptr_to_slot(pl3e))) )
{
@@ -1554,13 +1600,16 @@ static int mod_l3_entry(l3_pgentry_t *pl
if ( is_pv_32bit_domain(d) && (pgentry_ptr_to_slot(pl3e) >= 3) )
return 0;
+ page_lock(l3pg);
+
if ( unlikely(__copy_from_user(&ol3e, pl3e, sizeof(ol3e)) != 0) )
- return 0;
+ return page_unlock(l3pg), 0;
if ( l3e_get_flags(nl3e) & _PAGE_PRESENT )
{
if ( unlikely(l3e_get_flags(nl3e) & l3_disallow_mask(d)) )
{
+ page_unlock(l3pg);
MEM_LOG("Bad L3 flags %x",
l3e_get_flags(nl3e) & l3_disallow_mask(d));
return 0;
@@ -1570,23 +1619,26 @@ static int mod_l3_entry(l3_pgentry_t *pl
if ( !l3e_has_changed(ol3e, nl3e, _PAGE_PRESENT) )
{
adjust_guest_l3e(nl3e, d);
- return UPDATE_ENTRY(l3, pl3e, ol3e, nl3e, pfn, curr, preserve_ad);
+ rc = UPDATE_ENTRY(l3, pl3e, ol3e, nl3e, pfn, curr, preserve_ad);
+ page_unlock(l3pg);
+ return rc;
}
if ( unlikely(!get_page_from_l3e(nl3e, pfn, d)) )
- return 0;
+ return page_unlock(l3pg), 0;
adjust_guest_l3e(nl3e, d);
if ( unlikely(!UPDATE_ENTRY(l3, pl3e, ol3e, nl3e, pfn, curr,
preserve_ad)) )
{
- put_page_from_l3e(nl3e, pfn);
- return 0;
+ ol3e = nl3e;
+ rc = 0;
}
}
else if ( unlikely(!UPDATE_ENTRY(l3, pl3e, ol3e, nl3e, pfn, curr,
preserve_ad)) )
{
+ page_unlock(l3pg);
return 0;
}
@@ -1595,8 +1647,9 @@ static int mod_l3_entry(l3_pgentry_t *pl
pae_flush_pgd(pfn, pgentry_ptr_to_slot(pl3e), nl3e);
+ page_unlock(l3pg);
put_page_from_l3e(ol3e, pfn);
- return 1;
+ return rc;
}
#endif
@@ -1612,6 +1665,8 @@ static int mod_l4_entry(l4_pgentry_t *pl
struct vcpu *curr = current;
struct domain *d = curr->domain;
l4_pgentry_t ol4e;
+ struct page_info *l4pg = mfn_to_page(pfn);
+ int rc = 1;
if ( unlikely(!is_guest_l4_slot(d, pgentry_ptr_to_slot(pl4e))) )
{
@@ -1619,13 +1674,16 @@ static int mod_l4_entry(l4_pgentry_t *pl
return 0;
}
+ page_lock(l4pg);
+
if ( unlikely(__copy_from_user(&ol4e, pl4e, sizeof(ol4e)) != 0) )
- return 0;
+ return page_unlock(l4pg), 0;
if ( l4e_get_flags(nl4e) & _PAGE_PRESENT )
{
if ( unlikely(l4e_get_flags(nl4e) & L4_DISALLOW_MASK) )
{
+ page_unlock(l4pg);
MEM_LOG("Bad L4 flags %x",
l4e_get_flags(nl4e) & L4_DISALLOW_MASK);
return 0;
@@ -1635,28 +1693,32 @@ static int mod_l4_entry(l4_pgentry_t *pl
if ( !l4e_has_changed(ol4e, nl4e, _PAGE_PRESENT) )
{
adjust_guest_l4e(nl4e, d);
- return UPDATE_ENTRY(l4, pl4e, ol4e, nl4e, pfn, curr, preserve_ad);
+ rc = UPDATE_ENTRY(l4, pl4e, ol4e, nl4e, pfn, curr, preserve_ad);
+ page_unlock(l4pg);
+ return rc;
}
if ( unlikely(!get_page_from_l4e(nl4e, pfn, d)) )
- return 0;
+ return page_unlock(l4pg), 0;
adjust_guest_l4e(nl4e, d);
if ( unlikely(!UPDATE_ENTRY(l4, pl4e, ol4e, nl4e, pfn, curr,
preserve_ad)) )
{
- put_page_from_l4e(nl4e, pfn);
- return 0;
+ ol4e = nl4e;
+ rc = 0;
}
}
else if ( unlikely(!UPDATE_ENTRY(l4, pl4e, ol4e, nl4e, pfn, curr,
preserve_ad)) )
{
+ page_unlock(l4pg);
return 0;
}
+ page_unlock(l4pg);
put_page_from_l4e(ol4e, pfn);
- return 1;
+ return rc;
}
#endif
@@ -2184,8 +2246,6 @@ int do_mmuext_op(
rc = -ESRCH;
goto out;
}
-
- domain_lock(d);
for ( i = 0; i < count; i++ )
{
@@ -2434,8 +2494,6 @@ int do_mmuext_op(
process_deferred_ops();
- domain_unlock(d);
-
perfc_add(num_mmuext_ops, i);
out:
@@ -2488,8 +2546,6 @@ int do_mmu_update(
}
domain_mmap_cache_init(&mapcache);
-
- domain_lock(d);
for ( i = 0; i < count; i++ )
{
@@ -2663,8 +2719,6 @@ int do_mmu_update(
process_deferred_ops();
- domain_unlock(d);
-
domain_mmap_cache_destroy(&mapcache);
perfc_add(num_page_updates, i);
@@ -2717,13 +2771,18 @@ static int create_grant_pte_mapping(
goto failed;
}
+ page_lock(page);
+
ol1e = *(l1_pgentry_t *)va;
if ( !UPDATE_ENTRY(l1, (l1_pgentry_t *)va, ol1e, nl1e, mfn, v, 0) )
{
+ page_unlock(page);
put_page_type(page);
rc = GNTST_general_error;
goto failed;
}
+
+ page_unlock(page);
if ( !paging_mode_refcounts(d) )
put_page_from_l1e(ol1e, d);
@@ -2768,16 +2827,14 @@ static int destroy_grant_pte_mapping(
goto failed;
}
- if ( __copy_from_user(&ol1e, (l1_pgentry_t *)va, sizeof(ol1e)) )
- {
- put_page_type(page);
- rc = GNTST_general_error;
- goto failed;
- }
+ page_lock(page);
+
+ ol1e = *(l1_pgentry_t *)va;
/* Check that the virtual address supplied is actually mapped to frame. */
if ( unlikely((l1e_get_intpte(ol1e) >> PAGE_SHIFT) != frame) )
{
+ page_unlock(page);
MEM_LOG("PTE entry %lx for address %"PRIx64" doesn't match frame %lx",
(unsigned long)l1e_get_intpte(ol1e), addr, frame);
put_page_type(page);
@@ -2792,12 +2849,14 @@ static int destroy_grant_pte_mapping(
d->vcpu[0] /* Change if we go to per-vcpu shadows. */,
0)) )
{
+ page_unlock(page);
MEM_LOG("Cannot delete PTE entry at %p", va);
put_page_type(page);
rc = GNTST_general_error;
goto failed;
}
+ page_unlock(page);
put_page_type(page);
failed:
@@ -2813,6 +2872,7 @@ static int create_grant_va_mapping(
l1_pgentry_t *pl1e, ol1e;
struct domain *d = v->domain;
unsigned long gl1mfn;
+ struct page_info *l1pg;
int okay;
ASSERT(domain_is_locked(d));
@@ -2825,8 +2885,11 @@ static int create_grant_va_mapping(
MEM_LOG("Could not find L1 PTE for address %lx", va);
return GNTST_general_error;
}
+ l1pg = mfn_to_page(gl1mfn);
+ page_lock(l1pg);
ol1e = *pl1e;
okay = UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, v, 0);
+ page_unlock(l1pg);
guest_unmap_l1e(v, pl1e);
pl1e = NULL;
@@ -2844,6 +2907,7 @@ static int replace_grant_va_mapping(
{
l1_pgentry_t *pl1e, ol1e;
unsigned long gl1mfn;
+ struct page_info *l1pg;
int rc = 0;
pl1e = guest_map_l1e(v, addr, &gl1mfn);
@@ -2852,11 +2916,15 @@ static int replace_grant_va_mapping(
MEM_LOG("Could not find L1 PTE for address %lx", addr);
return GNTST_general_error;
}
+
+ l1pg = mfn_to_page(gl1mfn);
+ page_lock(l1pg);
ol1e = *pl1e;
/* Check that the virtual address supplied is actually mapped to frame. */
if ( unlikely(l1e_get_pfn(ol1e) != frame) )
{
+ page_unlock(l1pg);
MEM_LOG("PTE entry %lx for address %lx doesn't match frame %lx",
l1e_get_pfn(ol1e), addr, frame);
rc = GNTST_general_error;
@@ -2866,10 +2934,13 @@ static int replace_grant_va_mapping(
/* Delete pagetable entry. */
if ( unlikely(!UPDATE_ENTRY(l1, pl1e, ol1e, nl1e, gl1mfn, v, 0)) )
{
+ page_unlock(l1pg);
MEM_LOG("Cannot delete PTE entry at %p", (unsigned long *)pl1e);
rc = GNTST_general_error;
goto out;
}
+
+ page_unlock(l1pg);
out:
guest_unmap_l1e(v, pl1e);
@@ -2905,6 +2976,7 @@ int replace_grant_host_mapping(
struct vcpu *curr = current;
l1_pgentry_t *pl1e, ol1e;
unsigned long gl1mfn;
+ struct page_info *l1pg;
int rc;
if ( flags & GNTMAP_contains_pte )
@@ -2926,16 +2998,21 @@ int replace_grant_host_mapping(
(unsigned long)new_addr);
return GNTST_general_error;
}
+
+ l1pg = mfn_to_page(gl1mfn);
+ page_lock(l1pg);
ol1e = *pl1e;
if ( unlikely(!UPDATE_ENTRY(l1, pl1e, ol1e, l1e_empty(),
gl1mfn, curr, 0)) )
{
+ page_unlock(l1pg);
MEM_LOG("Cannot delete PTE entry at %p", (unsigned long *)pl1e);
guest_unmap_l1e(curr, pl1e);
return GNTST_general_error;
}
+ page_unlock(l1pg);
guest_unmap_l1e(curr, pl1e);
rc = replace_grant_va_mapping(addr, frame, ol1e, curr);
@@ -3013,8 +3090,6 @@ int do_update_va_mapping(unsigned long v
if ( rc )
return rc;
- domain_lock(d);
-
pl1e = guest_map_l1e(v, va, &gl1mfn);
if ( unlikely(!pl1e || !mod_l1_entry(pl1e, val, gl1mfn, 0)) )
@@ -3025,8 +3100,6 @@ int do_update_va_mapping(unsigned long v
pl1e = NULL;
process_deferred_ops();
-
- domain_unlock(d);
switch ( flags & UVMF_FLUSHTYPE_MASK )
{
@@ -3647,8 +3720,6 @@ int ptwr_do_page_fault(struct vcpu *v, u
struct ptwr_emulate_ctxt ptwr_ctxt;
int rc;
- domain_lock(d);
-
/* Attempt to read the PTE that maps the VA being accessed. */
guest_get_eff_l1e(v, addr, &pte);
page = l1e_get_page(pte);
@@ -3668,16 +3739,16 @@ int ptwr_do_page_fault(struct vcpu *v, u
ptwr_ctxt.cr2 = addr;
ptwr_ctxt.pte = pte;
+ page_lock(page);
rc = x86_emulate(&ptwr_ctxt.ctxt, &ptwr_emulate_ops);
+ page_unlock(page);
if ( rc == X86EMUL_UNHANDLEABLE )
goto bail;
- domain_unlock(d);
perfc_incr(ptwr_emulations);
return EXCRET_fault_fixed;
bail:
- domain_unlock(d);
return 0;
}
diff -r 98ed32885ec0 -r 09dd5999401b xen/include/asm-x86/mm.h
--- a/xen/include/asm-x86/mm.h Thu Jun 12 17:57:03 2008 +0100
+++ b/xen/include/asm-x86/mm.h Thu Jun 12 18:14:00 2008 +0100
@@ -46,6 +46,10 @@ struct page_info
} u;
+#if defined(__x86_64__)
+ spinlock_t lock;
+#endif
+
union {
/*
* Timestamp from 'TLB clock', used to avoid extra safety flushes.
@@ -61,10 +65,6 @@ struct page_info
*/
u32 shadow_flags;
};
-
-#if defined(__x86_64__)
- spinlock_t lock;
-#endif
};
/* The following page types are MUTUALLY EXCLUSIVE. */
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