[PATCH v3 5/5] monitor: increase amount of data for monitor to read

[Andrey Shinkevich via <qemu-devel@nongnu.org>]

QMP and HMP monitors read one byte at a time from the socket or stdin,
which is very inefficient. With 100+ VMs on the host, this results in
multiple extra system calls and CPU overuse.
This patch increases the amount of read data up to 4096 bytes that fits
the buffer size on the channel level.

Suggested-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
---
 monitor/monitor.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/monitor/monitor.c b/monitor/monitor.c
index 84222cd..43d2d3b 100644
--- a/monitor/monitor.c
+++ b/monitor/monitor.c
@@ -566,7 +566,7 @@ int monitor_can_read(void *opaque)
 {
     Monitor *mon = opaque;
 
-    return !qatomic_mb_read(&mon->suspend_cnt);
+    return !qatomic_mb_read(&mon->suspend_cnt) ? CHR_READ_BUF_LEN : 0;
 }
 
 void monitor_list_append(Monitor *mon)
-- 
1.8.3.1