Rusty Russell
2007-May-31 00:23 UTC
[PATCH 1/3] lguest: speed up PARAVIRT_LAZY_FLUSH handling
When Zach Amsden added PARAVIRT_LAZY_FLUSH I didn't realize how often
it would get called. We only need to do something if we're actually
in lazy mode.
Before:
Time for one context switch via pipe: 10509 (9863 - 18761)
Time for one Copy-on-Write fault: 71796 (20625 - 207750)
Time to exec client once: 1076218 (1066203 - 1085937)
Time for one fork/exit/wait: 1193125 (574750 - 1197750)
Time for two PTE updates: 10844 (10659 - 20703)
After:
Time for one context switch via pipe: 6745 (6521 - 13966)
Time for one Copy-on-Write fault: 44734 (11468 - 91988)
Time to exec client once: 815984 (801218 - 878218)
Time for one fork/exit/wait: 1023250 (397687 - 1030375)
Time for two PTE updates: 6699 (6475 - 9279)
(Native for comparison):
Time for one context switch via pipe: 4031 (3212 - 4146)
Time for one Copy-on-Write fault: 4402 (4388 - 4426)
Time to exec client once: 343859 (336859 - 349484)
Time for one fork/exit/wait: 120234 (118500 - 136140)
Time for two PTE updates: 2269 (2261 - 2272)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff -r 077496256739 drivers/lguest/lguest.c
--- a/drivers/lguest/lguest.c Thu May 31 16:34:17 2007 +1000
+++ b/drivers/lguest/lguest.c Thu May 31 16:36:23 2007 +1000
@@ -58,9 +58,10 @@ static enum paravirt_lazy_mode lazy_mode
static enum paravirt_lazy_mode lazy_mode;
static void lguest_lazy_mode(enum paravirt_lazy_mode mode)
{
- if (mode == PARAVIRT_LAZY_FLUSH)
- hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
- else {
+ if (mode == PARAVIRT_LAZY_FLUSH) {
+ if (unlikely(lazy_mode != PARAVIRT_LAZY_NONE))
+ hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
+ } else {
lazy_mode = mode;
if (mode == PARAVIRT_LAZY_NONE)
hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
Some hypercalls can be batched: lazy_hcall is the wrapper which
determines this, so it's pretty harmless to use lazy_hcall() instead of
hcall().
Before:
Time for one context switch via pipe: 6745 (6521 - 13966)
After:
Time for one context switch via pipe: 5406 (5170 - 7467)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
drivers/lguest/lguest.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
==================================================================---
a/drivers/lguest/lguest.c
+++ b/drivers/lguest/lguest.c
@@ -225,7 +225,7 @@ static unsigned long current_cr0, curren
static unsigned long current_cr0, current_cr3;
static void lguest_write_cr0(unsigned long val)
{
- hcall(LHCALL_TS, val & 8, 0, 0);
+ lazy_hcall(LHCALL_TS, val & 8, 0, 0);
current_cr0 = val;
}
@@ -247,7 +247,7 @@ static unsigned long lguest_read_cr2(voi
static void lguest_write_cr3(unsigned long cr3)
{
- hcall(LHCALL_NEW_PGTABLE, cr3, 0, 0);
+ lazy_hcall(LHCALL_NEW_PGTABLE, cr3, 0, 0);
current_cr3 = cr3;
}
@@ -287,7 +287,7 @@ static void lguest_set_pte(pte_t *ptep,
*ptep = pteval;
/* Don't bother with hypercall before initial setup. */
if (current_cr3)
- hcall(LHCALL_FLUSH_TLB, 1, 0, 0);
+ lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0);
}
static void lguest_flush_tlb_single(unsigned long addr)