# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1257794179 0
# Node ID 7cfe986d0cc69f29b3041e8900e3a71607944d6a
# Parent 139a8a2536589b8555ef16cc24dda2ddb6802530
Remus: Buffer checkpoint data locally until domain has resumed execution.
Signed-off-by: Brendan Cully <brendan@xxxxxxxxx>
---
tools/libxc/xc_domain_save.c | 113 ++++++++++++++++++++++++++++++++++++++++++-
1 files changed, 112 insertions(+), 1 deletion(-)
diff -r 139a8a253658 -r 7cfe986d0cc6 tools/libxc/xc_domain_save.c
--- a/tools/libxc/xc_domain_save.c Mon Nov 09 19:15:34 2009 +0000
+++ b/tools/libxc/xc_domain_save.c Mon Nov 09 19:16:19 2009 +0000
@@ -52,6 +52,15 @@ static unsigned long m2p_mfn0;
/* Address size of the guest */
unsigned int guest_width;
+/* buffer for output */
+struct outbuf {
+ void* buf;
+ size_t size;
+ size_t pos;
+};
+
+#define OUTBUF_SIZE (16384 * 1024)
+
/* grep fodder: machine_to_phys */
#define mfn_to_pfn(_mfn) (live_m2p[(_mfn)])
@@ -152,6 +161,85 @@ static int noncached_write(int fd, int l
}
return rc;
+}
+
+static int outbuf_init(struct outbuf* ob, size_t size)
+{
+ memset(ob, 0, sizeof(*ob));
+
+ if ( !(ob->buf = malloc(size)) ) {
+ DPRINTF("error allocating output buffer of size %zu\n", size);
+ return -1;
+ }
+
+ ob->size = size;
+
+ return 0;
+}
+
+static inline int outbuf_write(struct outbuf* ob, void* buf, size_t len)
+{
+ if ( len > ob->size - ob->pos ) {
+ DPRINTF("outbuf_write: %zu > %zu@%zu\n", len, ob->size - ob->pos,
ob->pos);
+ return -1;
+ }
+
+ memcpy(ob->buf + ob->pos, buf, len);
+ ob->pos += len;
+
+ return 0;
+}
+
+/* prep for nonblocking I/O */
+static int outbuf_flush(struct outbuf* ob, int fd)
+{
+ int rc;
+ int cur = 0;
+
+ if ( !ob->pos )
+ return 0;
+
+ rc = write(fd, ob->buf, ob->pos);
+ while (rc < 0 || cur + rc < ob->pos) {
+ if (rc < 0 && errno != EAGAIN && errno != EINTR) {
+ DPRINTF("error flushing output: %d\n", errno);
+ return -1;
+ }
+ if (rc > 0)
+ cur += rc;
+
+ rc = write(fd, ob->buf + cur, ob->pos - cur);
+ }
+
+ ob->pos = 0;
+
+ return 0;
+}
+
+/* if there's no room in the buffer, flush it and try again. */
+static inline int outbuf_hardwrite(struct outbuf* ob, int fd, void* buf,
+ size_t len)
+{
+ if ( !len )
+ return 0;
+
+ if ( !outbuf_write(ob, buf, len) )
+ return 0;
+
+ if ( outbuf_flush(ob, fd) < 0 )
+ return -1;
+
+ return outbuf_write(ob, buf, len);
+}
+
+/* start buffering output once we've reached checkpoint mode. */
+static inline int write_buffer(int dobuf, struct outbuf* ob, int fd, void* buf,
+ size_t len)
+{
+ if ( dobuf )
+ return outbuf_hardwrite(ob, fd, buf, len);
+ else
+ return write_exact(fd, buf, len);
}
#ifdef ADAPTIVE_SAVE
@@ -246,6 +334,16 @@ static int ratewrite(int io_fd, int live
#endif
+/* like write_buffer for ratewrite, which returns number of bytes written */
+static inline int ratewrite_buffer(int dobuf, struct outbuf* ob, int fd,
+ int live, void* buf, size_t len)
+{
+ if ( dobuf )
+ return outbuf_hardwrite(ob, fd, buf, len) ? -1 : len;
+ else
+ return ratewrite(fd, live, buf, len);
+}
+
static int print_stats(int xc_handle, uint32_t domid, int pages_sent,
xc_shadow_op_stats_t *stats, int print)
{
@@ -796,6 +894,10 @@ int xc_domain_save(int xc_handle, int io
unsigned long mfn;
+ struct outbuf ob;
+
+ outbuf_init(&ob, OUTBUF_SIZE);
+
/* If no explicit control parameters given, use defaults */
max_iters = max_iters ? : DEF_MAX_ITERS;
max_factor = max_factor ? : DEF_MAX_FACTOR;
@@ -995,6 +1097,12 @@ int xc_domain_save(int xc_handle, int io
}
copypages:
+#define write_exact(fd, buf, len) write_buffer(last_iter, &ob, (fd), (buf),
(len))
+#ifdef ratewrite
+#undef ratewrite
+#endif
+#define ratewrite(fd, live, buf, len) ratewrite_buffer(last_iter, &ob, (fd),
(live), (buf), (len))
+
/* Now write out each data page, canonicalising page tables as we go... */
for ( ; ; )
{
@@ -1594,7 +1702,10 @@ int xc_domain_save(int xc_handle, int io
callbacks->postcopy(callbacks->data);
/* Flush last write and discard cache for file. */
- discard_file_cache(io_fd, 1 /* flush */);
+ if ( outbuf_flush(&ob, io_fd) < 0 ) {
+ ERROR("Error when flushing output buffer\n");
+ rc = 1;
+ }
/* checkpoint_cb can spend arbitrarily long in between rounds */
if (!rc && callbacks->checkpoint &&
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