From b3ea2bdb792f6d961ba3adf45cf1f0c63c61e09d Mon Sep 17 00:00:00 2001
From: Orit Wasserman <owasserm@redhat.com>
Date: Fri, 22 Mar 2013 16:48:00 +0200
Subject: [PATCH] Store the data to send also in iovec

All data is still copied into the static buffer.
Adjacent iovecs are coalesced so we send one big buffer
instead of many small buffers.

Signed-off-by: Orit Wasserman <owasserm@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
---
 savevm.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/savevm.c b/savevm.c
index 5ab256c97d..aaaf39a678 100644
--- a/savevm.c
+++ b/savevm.c
@@ -114,6 +114,7 @@ void qemu_announce_self(void)
 /* savevm/loadvm support */
 
 #define IO_BUF_SIZE 32768
+#define MAX_IOV_SIZE MIN(IOV_MAX, 64)
 
 struct QEMUFile {
     const QEMUFileOps *ops;
@@ -129,6 +130,9 @@ struct QEMUFile {
     int buf_size; /* 0 when writing */
     uint8_t buf[IO_BUF_SIZE];
 
+    struct iovec iov[MAX_IOV_SIZE];
+    unsigned int iovcnt;
+
     int last_error;
 };
 
@@ -528,6 +532,7 @@ static void qemu_fflush(QEMUFile *f)
             f->pos += f->buf_index;
         }
         f->buf_index = 0;
+        f->iovcnt = 0;
     }
     if (ret < 0) {
         qemu_file_set_error(f, ret);
@@ -601,6 +606,18 @@ int qemu_fclose(QEMUFile *f)
     return ret;
 }
 
+static void add_to_iovec(QEMUFile *f, const uint8_t *buf, int size)
+{
+    /* check for adjacent buffer and coalesce them */
+    if (f->iovcnt > 0 && buf == f->iov[f->iovcnt - 1].iov_base +
+        f->iov[f->iovcnt - 1].iov_len) {
+        f->iov[f->iovcnt - 1].iov_len += size;
+    } else {
+        f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
+        f->iov[f->iovcnt++].iov_len = size;
+    }
+}
+
 void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
 {
     int l;
@@ -620,12 +637,13 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size)
         if (l > size)
             l = size;
         memcpy(f->buf + f->buf_index, buf, l);
+        add_to_iovec(f, f->buf + f->buf_index, l);
         f->is_write = 1;
         f->buf_index += l;
         f->bytes_xfer += l;
         buf += l;
         size -= l;
-        if (f->buf_index >= IO_BUF_SIZE) {
+        if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
             qemu_fflush(f);
             if (qemu_file_get_error(f)) {
                 break;
@@ -650,7 +668,9 @@ void qemu_put_byte(QEMUFile *f, int v)
     f->is_write = 1;
     f->bytes_xfer++;
 
-    if (f->buf_index >= IO_BUF_SIZE) {
+    add_to_iovec(f, f->buf + (f->buf_index - 1), 1);
+
+    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
         qemu_fflush(f);
     }
 }