From a32a8813d0173163ba44d8f9556e0d89fdc4fb46 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 12 Jun 2009 22:27:02 -0600 Subject: 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 --- include/linux/lguest.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'include/linux') diff --git a/include/linux/lguest.h b/include/linux/lguest.h index 175e63f4a8c0..7bc1440fc473 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. */ -- cgit v1.2.3 From df60aeef4f4fe0645d9a195a7689005520422de5 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 12 Jun 2009 22:27:09 -0600 Subject: lguest: use eventfds for device notification Currently, when a Guest wants to perform I/O it calls LHCALL_NOTIFY with an address: the main Launcher process returns with this address, and figures out what device to run. A far nicer model is to let processes bind an eventfd to an address: if we find one, we simply signal the eventfd. Signed-off-by: Rusty Russell Cc: Davide Libenzi --- include/linux/lguest_launcher.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/lguest_launcher.h b/include/linux/lguest_launcher.h index a53407a4165c..9de964b90586 100644 --- a/include/linux/lguest_launcher.h +++ b/include/linux/lguest_launcher.h @@ -58,6 +58,7 @@ enum lguest_req LHREQ_GETDMA, /* No longer used */ LHREQ_IRQ, /* + irq */ LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */ + LHREQ_EVENTFD, /* + address, fd. */ }; /* The alignment to use between consumer and producer parts of vring. -- cgit v1.2.3 From 5dac051bc6030963181b69faddd9e0ad04f85fa8 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Fri, 12 Jun 2009 22:27:10 -0600 Subject: lguest: remove obsolete LHREQ_BREAK call We no longer need an efficient mechanism to force the Guest back into host userspace, as each device is serviced without bothering the main Guest process (aka. the Launcher). Signed-off-by: Rusty Russell --- include/linux/lguest_launcher.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/lguest_launcher.h b/include/linux/lguest_launcher.h index 9de964b90586..bfefbdf7498a 100644 --- a/include/linux/lguest_launcher.h +++ b/include/linux/lguest_launcher.h @@ -57,7 +57,7 @@ enum lguest_req LHREQ_INITIALIZE, /* + base, pfnlimit, start */ LHREQ_GETDMA, /* No longer used */ LHREQ_IRQ, /* + irq */ - LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */ + LHREQ_BREAK, /* No longer used */ LHREQ_EVENTFD, /* + address, fd. */ }; -- cgit v1.2.3