[PATCH v3 11/12] kvm tools: Modify term_putc to write more than one char

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From: David Daney <david.daney@xxxxxxxxxx>

It is a performance enhancement. When running in a simulator, each
system call to write a character takes a lot of time.  Batching them
up decreases the overhead (in the root kernel) of each virtio console
write.

Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
Signed-off-by: Andreas Herrmann <andreas.herrmann@xxxxxxxxxxxxxxxxxx>
---
 tools/kvm/term.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/kvm/term.c b/tools/kvm/term.c
index 3de410b..b153eed 100644
--- a/tools/kvm/term.c
+++ b/tools/kvm/term.c
@@ -52,11 +52,14 @@ int term_getc(struct kvm *kvm, int term)
 int term_putc(char *addr, int cnt, int term)
 {
 	int ret;
+	int num_remaining = cnt;
 
-	while (cnt--) {
-		ret = write(term_fds[term][TERM_FD_OUT], addr++, 1);
+	while (num_remaining) {
+		ret = write(term_fds[term][TERM_FD_OUT], addr, num_remaining);
 		if (ret < 0)
 			return 0;
+		num_remaining -= ret;
+		addr += ret;
 	}
 
 	return cnt;
-- 
1.7.9.5



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