Re: [Qemu-devel] [RFC 10/12] Add qemu_put_buffer_no_copy

[Michael R. Hines]

Can you add a "flag" or something to indicate that the iov pointer 
belongs to RAM and not to device state?

That way, I could re-use this code for RDMA - if I see this flag, I will 
know to send to RDMA.....

- Michael


On 03/21/2013 05:09 AM, Orit Wasserman wrote:
This allow us to add a buffer to the iovec to send without copying it
into the static buffer.

Signed-off-by: Orit Wasserman <owass...@redhat.com>
---
  include/migration/qemu-file.h |  5 +++++
  savevm.c                      | 42 ++++++++++++++++++++++++------------------
  2 files changed, 29 insertions(+), 18 deletions(-)

diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 8d3da9b..5168be2 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -75,6 +75,11 @@ int qemu_fclose(QEMUFile *f);
  int64_t qemu_ftell(QEMUFile *f);
  void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size);
  void qemu_put_byte(QEMUFile *f, int v);
+/*
+ * put_buffer without copying the buffer.
+ * The buffer should be available till it is sent.
+ */
+void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size);

  static inline void qemu_put_ubyte(QEMUFile *f, unsigned int v)
  {
diff --git a/savevm.c b/savevm.c
index 40d96f4..32a506e 100644
--- a/savevm.c
+++ b/savevm.c
@@ -629,6 +629,22 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int 
size)
  {
      int l;

+    while (size > 0) {
+        l = IO_BUF_SIZE - f->buf_index;
+        if (l > size) {
+            l = size;
+        }
+        memcpy(f->buf + f->buf_index, buf, l);
+        f->buf_index += l;
+        f->is_write = 1;
+        qemu_put_buffer_no_copy(f, f->buf + (f->buf_index - l), l);
+        buf += l;
+        size -= l;
+    }
+}
+
+void qemu_put_buffer_no_copy(QEMUFile *f, const uint8_t *buf, int size)
+{
      if (f->last_error) {
          return;
      }
@@ -639,24 +655,14 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int 
size)
          abort();
      }

-    while (size > 0) {
-        l = IO_BUF_SIZE - f->buf_index;
-        if (l > size)
-            l = size;
-        memcpy(f->buf + f->buf_index, buf, l);
-        f->iov[f->iovcnt].iov_base = f->buf + f->buf_index;
-        f->iov[f->iovcnt++].iov_len = l;
-        f->is_write = 1;
-        f->buf_index += l;
-        f->bytes_xfer += l;
-        buf += l;
-        size -= l;
-        if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
-            qemu_fflush(f);
-            if (qemu_file_get_error(f)) {
-                break;
-            }
-        }
+    f->iov[f->iovcnt].iov_base = (uint8_t *)buf;
+    f->iov[f->iovcnt++].iov_len = size;
+
+    f->is_write = 1;
+    f->bytes_xfer += size;
+
+    if (f->buf_index >= IO_BUF_SIZE || f->iovcnt >= MAX_IOV_SIZE) {
+        qemu_fflush(f);
      }
  }