On 02/06/2010 17:18, "Ian Jackson" <Ian.Jackson@xxxxxxxxxxxxx> wrote:
> Andreas Olsowski writes ("[Xen-devel] slow live magration / xc_restore on xen4
> pvops"):
>> [2010-06-01 21:20:57 5211] INFO (XendCheckpoint:423) ERROR Internal
>> error: Error when reading batch size
>> [2010-06-01 21:20:57 5211] INFO (XendCheckpoint:423) ERROR Internal
>> error: error when buffering batch, finishing
>
> These errors, and the slowness of migrations, are caused by changes
> made to support Remus. Previously, a migration would be regarded as
> complete as soon as the final information including CPU states was
> received at the migration target. xc_domain_restore would return
> immediately at that point.
This probably needs someone with Remus knowledge to take a look, to keep all
cases working correctly. I'll Cc Brendan. It'd be good to get this fixed for
a 4.0.1 in a few weeks.
-- Keir
> Since the Remus patches, xc_domain_restore waits until it gets an IO
> error, and also has a very short timeout which induces IO errors if
> nothing is received if there is no timeout. This is correct in the
> Remus case but wrong in the normal case.
>
> The code should be changed so that xc_domain_restore
> (a) takes an explicit parameter for the IO timeout, which
> should default to something much longer than the 100ms or so of
> the Remus case, and
> (b) gets told whether
> (i) it should return immediately after receiving the "tail"
> which contains the CPU state; or
> (ii) it should attempt to keep reading after receiving the "tail"
> and only return when the connection fails.
>
> In the case (b)(i), which should be the usual case, the behaviour
> should be that which we would get if changeset 20406:0f893b8f7c15 was
> reverted. The offending code is mostly this, from 20406:
>
> + // DPRINTF("Buffered checkpoint\n");
> +
> + if ( pagebuf_get(&pagebuf, io_fd, xc_handle, dom) ) {
> + ERROR("error when buffering batch, finishing\n");
> + goto finish;
> + }
> + memset(&tmptail, 0, sizeof(tmptail));
> + if ( buffer_tail(&tmptail, io_fd, max_vcpu_id, vcpumap,
> + ext_vcpucontext) < 0 ) {
> + ERROR ("error buffering image tail, finishing");
> + goto finish;
> + }
> + tailbuf_free(&tailbuf);
> + memcpy(&tailbuf, &tmptail, sizeof(tailbuf));
> +
> + goto loadpages;
> +
> + finish:
>
> Ian.
>
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