On Mon, Sep 6, 2010 at 11:03 AM, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> # HG changeset patch
> # User Ian Campbell <ian.campbell@xxxxxxxxxx>
> # Date 1283766891 -3600
> # Node ID bdf8ce09160d715451e1204babe5f80886ea6183
> # Parent 5f96f36feebdb87eaadbbcab0399f32eda86f735
> libxc: provide notification of final checkpoint to restore end
>
> When the restore code sees this notification it will restore the
> currently in-progress checkpoint when it completes.
>
> This allows the restore end to finish up without waiting for a
> spurious timeout on the receive fd and thereby avoids unnecessary
> error logging in the case of a successful migration or restore.
>
> In the normal migration or restore case the first checkpoint is always
> the last. For a rolling checkpoint (such as Remus) the notification is
> currently unused but could be used in the future for example to
> provide a controlled failover for reasons other than error
Unfortunatley, this introduces a backwards-compatibility problem,
since older versions of the tools never send LAST_CHECKPOINT.
Would it make sense to invert the logic on this -- i.e., default to
only one checkpoint, and send "MORE_CHECKPOINTS" if it expects this
*not* to be the last (either by expecting the checkpoint() function to
do it, or by sending it from xc_domain_save)?
Now that 4.1 is out, we have to consider version compatibilities. But
we should be able to make it so that there would only be if:
1) You're running REMUS
2) One of your toolstacks is 4.1.0, and one is not.
That seems like it shouldn't be too bad.
Thoughts?
-George
>
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Acked-by: Brendan Cully <brendan@xxxxxxxxx>
>
> diff -r 5f96f36feebd -r bdf8ce09160d tools/libxc/xc_domain_restore.c
> --- a/tools/libxc/xc_domain_restore.c Mon Sep 06 10:54:51 2010 +0100
> +++ b/tools/libxc/xc_domain_restore.c Mon Sep 06 10:54:51 2010 +0100
> @@ -42,6 +42,7 @@ struct restore_ctx {
> xen_pfn_t *p2m; /* A table mapping each PFN to its new MFN. */
> xen_pfn_t *p2m_batch; /* A table of P2M mappings in the current region.
> */
> int completed; /* Set when a consistent image is available */
> + int last_checkpoint; /* Set when we should commit to the current
> checkpoint when it completes. */
> struct domain_info_context dinfo;
> };
>
> @@ -765,6 +766,11 @@ static int pagebuf_get_one(xc_interface
> // DPRINTF("console pfn location: %llx\n", buf->console_pfn);
> return pagebuf_get_one(xch, ctx, buf, fd, dom);
>
> + case XC_SAVE_ID_LAST_CHECKPOINT:
> + ctx->last_checkpoint = 1;
> + // DPRINTF("last checkpoint indication received");
> + return pagebuf_get_one(xch, ctx, buf, fd, dom);
> +
> default:
> if ( (count > MAX_BATCH_SIZE) || (count < 0) ) {
> ERROR("Max batch size exceeded (%d). Giving up.", count);
> @@ -1296,10 +1302,23 @@ int xc_domain_restore(xc_interface *xch,
> goto out;
> }
> ctx->completed = 1;
> - /* shift into nonblocking mode for the remainder */
> - if ( (flags = fcntl(io_fd, F_GETFL,0)) < 0 )
> - flags = 0;
> - fcntl(io_fd, F_SETFL, flags | O_NONBLOCK);
> +
> + /*
> + * If more checkpoints are expected then shift into
> + * nonblocking mode for the remainder.
> + */
> + if ( !ctx->last_checkpoint )
> + {
> + if ( (flags = fcntl(io_fd, F_GETFL,0)) < 0 )
> + flags = 0;
> + fcntl(io_fd, F_SETFL, flags | O_NONBLOCK);
> + }
> + }
> +
> + if ( ctx->last_checkpoint )
> + {
> + // DPRINTF("Last checkpoint, finishing\n");
> + goto finish;
> }
>
> // DPRINTF("Buffered checkpoint\n");
> diff -r 5f96f36feebd -r bdf8ce09160d tools/libxc/xc_domain_save.c
> --- a/tools/libxc/xc_domain_save.c Mon Sep 06 10:54:51 2010 +0100
> +++ b/tools/libxc/xc_domain_save.c Mon Sep 06 10:54:51 2010 +0100
> @@ -1616,6 +1616,20 @@ int xc_domain_save(xc_interface *xch, in
> }
> }
>
> + if ( !callbacks->checkpoint )
> + {
> + /*
> + * If this is not a checkpointed save then this must be the first and
> + * last checkpoint.
> + */
> + i = XC_SAVE_ID_LAST_CHECKPOINT;
> + if ( wrexact(io_fd, &i, sizeof(int)) )
> + {
> + PERROR("Error when writing last checkpoint chunk");
> + goto out;
> + }
> + }
> +
> /* Zero terminate */
> i = 0;
> if ( wrexact(io_fd, &i, sizeof(int)) )
> diff -r 5f96f36feebd -r bdf8ce09160d tools/libxc/xg_save_restore.h
> --- a/tools/libxc/xg_save_restore.h Mon Sep 06 10:54:51 2010 +0100
> +++ b/tools/libxc/xg_save_restore.h Mon Sep 06 10:54:51 2010 +0100
> @@ -131,6 +131,7 @@
> #define XC_SAVE_ID_TMEM_EXTRA -6
> #define XC_SAVE_ID_TSC_INFO -7
> #define XC_SAVE_ID_HVM_CONSOLE_PFN -8 /* (HVM-only) */
> +#define XC_SAVE_ID_LAST_CHECKPOINT -9 /* Commit to restoring after
> completion of current iteration. */
>
> /*
> ** We process save/restore/migrate in batches of pages; the below
>
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>
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