diff options
| author | Rusty Russell <rusty@rustcorp.com.au> | 2009-06-12 22:27:02 -0600 |
|---|---|---|
| committer | Rusty Russell <rusty@rustcorp.com.au> | 2009-06-12 22:27:03 +0930 |
| commit | a32a8813d0173163ba44d8f9556e0d89fdc4fb46 (patch) | |
| tree | fddb6742338047d0219e8c2536cd39b04e643b16 /drivers/lguest/core.c | |
| parent | abd41f037e1a64543000ed73b42f616d04d92700 (diff) | |
| download | linux-a32a8813d0173163ba44d8f9556e0d89fdc4fb46.tar.bz2 | |
lguest: improve interrupt handling, speed up stream networking
lguest never checked for pending interrupts when enabling interrupts, and
things still worked. However, it makes a significant difference to TCP
performance, so it's time we fixed it by introducing a pending_irq flag
and checking it on irq_restore and irq_enable.
These two routines are now too big to patch into the 8/10 bytes
patch space, so we drop that code.
Note: The high latency on interrupt delivery had a very curious
effect: once everything else was optimized, networking without GSO was
faster than networking with GSO, since more interrupts were sent and
hence a greater chance of one getting through to the Guest!
Note2: (Almost) Closing the same loophole for iret doesn't have any
measurable effect, so I'm leaving that patch for the moment.
Before:
1GB tcpblast Guest->Host: 30.7 seconds
1GB tcpblast Guest->Host (no GSO): 76.0 seconds
After:
1GB tcpblast Guest->Host: 6.8 seconds
1GB tcpblast Guest->Host (no GSO): 27.8 seconds
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers/lguest/core.c')
| -rw-r--r-- | drivers/lguest/core.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index 8ca1def5b142..03fbc88c0023 100644 --- a/drivers/lguest/core.c +++ b/drivers/lguest/core.c @@ -189,6 +189,7 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) /* We stop running once the Guest is dead. */ while (!cpu->lg->dead) { unsigned int irq; + bool more; /* First we run any hypercalls the Guest wants done. */ if (cpu->hcall) @@ -213,9 +214,9 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) /* Check if there are any interrupts which can be delivered now: * if so, this sets up the hander to be executed when we next * run the Guest. */ - irq = interrupt_pending(cpu); + irq = interrupt_pending(cpu, &more); if (irq < LGUEST_IRQS) - try_deliver_interrupt(cpu, irq); + try_deliver_interrupt(cpu, irq, more); /* All long-lived kernel loops need to check with this horrible * thing called the freezer. If the Host is trying to suspend, @@ -233,7 +234,7 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) set_current_state(TASK_INTERRUPTIBLE); /* Just before we sleep, make sure nothing snuck in * which we should be doing. */ - if (interrupt_pending(cpu) < LGUEST_IRQS + if (interrupt_pending(cpu, &more) < LGUEST_IRQS || cpu->break_out) set_current_state(TASK_RUNNING); else |