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migration: use a single I/O operation when writev_buffer is not defined

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The recent patches to use vectored I/O for RAM migration caused a
regression in savevm speed.  To restore previous performance,
add data to the buffer in qemu_put_buffer_async whenever writev_buffer
is not available in the QEMUFile.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-04-08 13:29:55 +02:00 committed by Juan Quintela
parent af74db72d3
commit 7ce51f1b81
1 changed files with 34 additions and 15 deletions
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49
savevm.c
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@ -525,27 +525,24 @@ static void qemu_file_set_error(QEMUFile *f, int ret)
static void qemu_fflush(QEMUFile *f)
{
ssize_t ret = 0;
int i = 0;
if (!f->ops->writev_buffer && !f->ops->put_buffer) {
return;
}
if (f->is_write && f->iovcnt > 0) {
if (f->is_write) {
if (f->ops->writev_buffer) {
ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt);
if (ret >= 0) {
f->pos += ret;
if (f->iovcnt > 0) {
ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt);
}
} else {
for (i = 0; i < f->iovcnt && ret >= 0; i++) {
ret = f->ops->put_buffer(f->opaque, f->iov[i].iov_base, f->pos,
f->iov[i].iov_len);
if (ret >= 0) {
f->pos += ret;
}
if (f->buf_index > 0) {
ret = f->ops->put_buffer(f->opaque, f->buf, f->pos, f->buf_index);
}
}
if (ret >= 0) {
f->pos += ret;
}
f->buf_index = 0;
f->iovcnt = 0;
}
@ -640,6 +637,11 @@ static void add_to_iovec(QEMUFile *f, const uint8_t *buf, int size)
void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf, int size)
{
if (!f->ops->writev_buffer) {
qemu_put_buffer(f, buf, size);
return;
}
if (f->last_error) {
return;
}
@ -673,8 +675,17 @@ 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);
f->buf_index += l;
qemu_put_buffer_async(f, f->buf + (f->buf_index - l), l);
f->bytes_xfer += size;
if (f->ops->writev_buffer) {
add_to_iovec(f, f->buf + f->buf_index, l);
f->buf_index += l;
} else {
f->is_write = 1;
f->buf_index += l;
if (f->buf_index == IO_BUF_SIZE) {
qemu_fflush(f);
}
}
if (qemu_file_get_error(f)) {
break;
}
@ -697,8 +708,16 @@ void qemu_put_byte(QEMUFile *f, int v)
f->buf[f->buf_index] = v;
f->bytes_xfer++;
add_to_iovec(f, f->buf + f->buf_index, 1);
f->buf_index++;
if (f->ops->writev_buffer) {
add_to_iovec(f, f->buf + f->buf_index, 1);
f->buf_index++;
} else {
f->is_write = 1;
f->buf_index++;
if (f->buf_index == IO_BUF_SIZE) {
qemu_fflush(f);
}
}
}
static void qemu_file_skip(QEMUFile *f, int size)