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authorRusty Russell <rusty@rustcorp.com.au>2009-06-12 22:27:02 -0600
committerRusty Russell <rusty@rustcorp.com.au>2009-06-12 22:27:03 +0930
commita32a8813d0173163ba44d8f9556e0d89fdc4fb46 (patch)
treefddb6742338047d0219e8c2536cd39b04e643b16 /include/linux
parentabd41f037e1a64543000ed73b42f616d04d92700 (diff)
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 'include/linux')
-rw-r--r--include/linux/lguest.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/lguest.h b/include/linux/lguest.h
index 175e63f4a8c..7bc1440fc47 100644
--- a/include/linux/lguest.h
+++ b/include/linux/lguest.h
@@ -30,6 +30,10 @@ struct lguest_data
/* Wallclock time set by the Host. */
struct timespec time;
+ /* Interrupt pending set by the Host. The Guest should do a hypercall
+ * if it re-enables interrupts and sees this set (to X86_EFLAGS_IF). */
+ int irq_pending;
+
/* Async hypercall ring. Instead of directly making hypercalls, we can
* place them in here for processing the next time the Host wants.
* This batching can be quite efficient. */