On Wed, Nov 24, 2010 at 12:03:06AM +0100, Juan Quintela wrote:
> From: Juan Quintela <quint...@trasno.org>
>
> cheking each 64 pages is a random magic number as good as any other.
> We don't want to test too many times, but on the other hand,
> qemu_get_clock_ns() is not so expensive either.
>
Could you please explain what's the problem this fixes?
I would like to see an API that documents the contract
we are making with the backend.
> Signed-off-by: Juan Quintela <quint...@trasno.org>
> Signed-off-by: Juan Quintela <quint...@redhat.com>
> ---
> arch_init.c | 16 ++++++++++++++++
> 1 files changed, 16 insertions(+), 0 deletions(-)
>
> diff --git a/arch_init.c b/arch_init.c
> index d32aaae..b463798 100644
> --- a/arch_init.c
> +++ b/arch_init.c
> @@ -40,6 +40,7 @@
> #include "net.h"
> #include "gdbstub.h"
> #include "hw/smbios.h"
> +#include "buffered_file.h"
>
> #ifdef TARGET_SPARC
> int graphic_width = 1024;
> @@ -218,6 +219,7 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage,
> void *opaque)
> uint64_t bytes_transferred_last;
> uint64_t t0;
> double bwidth = 0;
> + int i;
>
> if (stage < 0) {
> cpu_physical_memory_set_dirty_tracking(0);
> @@ -261,6 +263,7 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage,
> void *opaque)
> bytes_transferred_last = bytes_transferred;
> t0 = qemu_get_clock_ns(rt_clock);
>
> + i = 0;
> while (!qemu_file_rate_limit(f)) {
> int bytes_sent;
>
> @@ -269,6 +272,19 @@ int ram_save_live(Monitor *mon, QEMUFile *f, int stage,
> void *opaque)
> if (bytes_sent == 0) { /* no more blocks */
> break;
> }
> + /* we want to check in the 1st loop, just in case it was the 1st time
> + and we had to sync the dirty bitmap.
> + qemu_get_clock_ns() is a bit expensive, so we only check each some
> + iterations
> + */
> + if ((i & 63) == 0) {
> + uint64_t t1 = (qemu_get_clock_ns(rt_clock) - t0) / 1000000;
This adds even more non-determinism to savevm behaviour. If bandwidth
limit is higth enough, I expect it to just keep going.
> + if (t1 > buffered_file_interval/2) {
arch_init should not depend on buffered_file implementation IMO.
Also - / 2?
> + printf("big delay %ld milliseconds, %d iterations\n", t1, i);
Is this a debugging aid?
> + break;
> + }
> + }
> + i++;
> }
>
> t0 = qemu_get_clock_ns(rt_clock) - t0;
> --
> 1.7.3.2
>
