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[Qemu-devel] [PATCH v3 1/3] Do not drop global mutex for polled main loo
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] [PATCH v3 1/3] Do not drop global mutex for polled main loop runs |
Date: |
Mon, 22 Aug 2011 17:46:01 +0200 |
If we call select without a timeout, it's more efficient to keep the
global mutex locked as we may otherwise just play ping pong with a
vcpu thread contending for it. This is particularly important for TCG
mode where we run in lock-step with the vcpu thread.
Signed-off-by: Jan Kiszka <address@hidden>
---
vl.c | 10 ++++++++--
1 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/vl.c b/vl.c
index 06a6f80..0e8b6a4 100644
--- a/vl.c
+++ b/vl.c
@@ -1349,9 +1349,15 @@ void main_loop_wait(int nonblocking)
qemu_iohandler_fill(&nfds, &rfds, &wfds, &xfds);
slirp_select_fill(&nfds, &rfds, &wfds, &xfds);
- qemu_mutex_unlock_iothread();
+ if (timeout > 0) {
+ qemu_mutex_unlock_iothread();
+ }
+
ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv);
- qemu_mutex_lock_iothread();
+
+ if (timeout > 0) {
+ qemu_mutex_lock_iothread();
+ }
qemu_iohandler_poll(&rfds, &wfds, &xfds, ret);
slirp_select_poll(&rfds, &wfds, &xfds, (ret < 0));
--
1.7.3.4