From: Ian Jackson <Ian.Jackson@eu.citrix.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Ross Lagerwall <ross.lagerwall@citrix.com>,
Wei Liu <wei.liu2@citrix.com>,
Ian Campbell <Ian.Campbell@citrix.com>,
Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH v3 17/28] tools/libxl: Infrastructure for reading a libxl migration v2 stream
Date: Mon, 13 Jul 2015 16:33:54 +0100 [thread overview]
Message-ID: <21923.55906.835814.413355@mariner.uk.xensource.com> (raw)
In-Reply-To: <55A3D0DE.3070905@citrix.com>
Andrew Cooper writes ("Re: [PATCH v3 17/28] tools/libxl: Infrastructure for reading a libxl migration v2 stream"):
> On 13/07/15 15:31, Ian Jackson wrote:
> > For example, there is also incoming_record, and record_queue (which
> > may be undefined, empty, one entry, >=2 entries), and the datacopier.
>
> These cannot be expressed in the above terms.
>
> incoming_record (as already noted in libxl_internal.h) is only used
> while reading a record, which happens in both Active/NORMAL and
> Active/BUFFERING
>
> record_queue is strictly 0 or 1 entries during NORMAL, grows from 0 to
> >=1 during BUFFERING, and shrinks back to 0 during UNBUFFERING.
>
> How would you go about expressing this without a state transition
> diagram? (I really don't think an ascii art state transition diagram
> will help make this any clearer)
* phase running in_ record incoming
* checkpoint _queue _record
*
* Undefined undef undef undef undef undef
* Idle undef false false 0 0
* Active NORMAL true false 0/1 0/partial
* Active BUFFERING true true any 0/partial
* Active UNBUFFERING true true any 0
Adjust to taste and to correspond to facts.
> > Is the datacopier always active ? I think it is except
> > - when we are processing one of our own callbacks, or
> > - in BUFFERING/UNBUFFERING, when process_record is setting up
> > its own callbacks
>
> The datacopier is only active while reading a record from the stream,
> but that is only (logically) half of the work to do. It will never be
> active when processing records.
>
> There is a second datacopier for qemu use which is only active while
> processing an EMULATOR record.
Maybe this wants to be in the table, or maybe it wants a comment next
to the variable name in the struct.
> > Maybe you want to say in a comment that there is always _either_ a
> > datacopier callback to come, _or_ a callback set up by process_record.
>
> ok.
I'm glad that I divined correctly that this is true :-).
> >> +static void stream_continue(libxl__egc *egc,
> >> + libxl__stream_read_state *stream)
> >> +{
> > ...
> >> + switch (stream->phase) {
> >> + case SRS_PHASE_NORMAL:
> >> + /*
> >> + * Normal phase (regular migration or restore from file):
> >> + *
> >> + * logically:
> >> + * do { read_record(); process_record(); } while ( not END );
> >> + *
> >> + * Alternate between reading a record from the stream, and
> >> + * processing the record. There should never be two records
> >> + * in the queue.
> >> + */
> >> + if (LIBXL_STAILQ_EMPTY(&stream->record_queue))
> >> + setup_read_record(egc, stream);
> >> + else {
> >> + if (process_record(egc, stream))
> >> + setup_read_record(egc, stream);
> >
> > Weren't you going to add an assert here, that the queue is empty ?
...
> It is in the paragraph below PHASE_NORMAL, which you have snipped.
I have grepped the whole of `stream_continue' in the tip of v3 of
your series (b8bf4572) and these are the results:
assert(stream->recursion_guard == false);
assert(stream->in_checkpoint);
assert(stream->in_checkpoint);
assert(stream->recursion_guard == true);
I meant a call to assert() which ensures that after process_record in
PHASE_NORMAL, the queue is empty.
Ian.
next prev parent reply other threads:[~2015-07-13 15:33 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-13 12:01 [PATCH v3 00/27] Libxl migration v2 Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 01/28] bsd-sys-queue-h-seddery: Massage `offsetof' Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 02/28] tools/libxc: Always compile the compat qemu variables into xc_sr_context Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 03/28] tools/libxl: Introduce ROUNDUP() Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 04/28] tools/libxl: Introduce libxl__kill() Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 05/28] tools/libxl: Stash all restore parameters in domain_create_state Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 06/28] tools/libxl: Split libxl__domain_create_state.restore_fd in two Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 07/28] tools/libxl: Extra management APIs for the save helper Andrew Cooper
2015-07-13 13:21 ` Ian Campbell
2015-07-13 15:01 ` Ian Jackson
2015-07-13 12:01 ` [PATCH v3 08/28] tools/libxl: Add save_helper_state pointers to libxl__xc_domain_{save, restore}() Andrew Cooper
2015-07-13 13:24 ` Ian Campbell
2015-07-13 12:01 ` [PATCH v3 09/28] tools/xl: Mandatory flag indicating the format of the migration stream Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 10/28] docs: Libxl migration v2 stream specification Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 11/28] tools/python: Libxc migration v2 infrastructure Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 12/28] tools/python: Libxl " Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 13/28] tools/python: Other migration infrastructure Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 14/28] tools/python: Verification utility for v2 stream spec compliance Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 15/28] tools/python: Conversion utility for legacy migration streams Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 16/28] tools/libxl: Migration v2 stream format Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 17/28] tools/libxl: Infrastructure for reading a libxl migration v2 stream Andrew Cooper
2015-07-13 13:42 ` Ian Campbell
2015-07-13 13:53 ` Andrew Cooper
2015-07-13 14:11 ` Ian Jackson
2015-07-13 14:03 ` Ian Jackson
2015-07-13 14:31 ` Ian Jackson
2015-07-13 14:53 ` Andrew Cooper
2015-07-13 15:33 ` Ian Jackson [this message]
2015-07-13 15:08 ` Ian Jackson
2015-07-13 15:13 ` Andrew Cooper
2015-07-13 15:35 ` Ian Jackson
2015-07-13 12:01 ` [PATCH v3 18/28] tools/libxl: Infrastructure to convert a legacy stream Andrew Cooper
2015-07-13 14:45 ` Ian Jackson
2015-07-13 15:08 ` Andrew Cooper
2015-07-13 15:44 ` Ian Jackson
2015-07-13 15:53 ` Andrew Cooper
2015-07-13 15:56 ` Ian Jackson
2015-07-13 16:04 ` Ian Campbell
2015-07-13 12:01 ` [PATCH v3 19/28] tools/libxl: Convert a legacy stream if needed Andrew Cooper
2015-07-13 14:51 ` Ian Jackson
2015-07-13 15:20 ` Andrew Cooper
2015-07-13 15:44 ` Ian Jackson
2015-07-13 12:01 ` [PATCH v3 20/28] tools/libxc+libxl+xl: Restore v2 streams Andrew Cooper
2015-07-13 15:02 ` Ian Jackson
2015-07-13 12:01 ` [PATCH v3 21/28] tools/libxl: Infrastructure for writing a v2 stream Andrew Cooper
2015-07-13 15:09 ` Ian Jackson
2015-07-13 15:21 ` Ian Jackson
2015-07-13 15:33 ` Andrew Cooper
2015-07-13 15:47 ` Ian Jackson
2015-07-13 15:56 ` Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 22/28] tools/libxc+libxl+xl: Save v2 streams Andrew Cooper
2015-07-13 15:25 ` Ian Jackson
2015-07-13 12:01 ` [PATCH v3 23/28] docs/libxl: Introduce CHECKPOINT_END to support migration v2 remus streams Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 24/28] tools/libxl: Write checkpoint records into the stream Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 25/28] tools/libx{c, l}: Introduce restore_callbacks.checkpoint() Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 26/28] tools/libxl: Handle checkpoint records in a libxl migration v2 stream Andrew Cooper
2015-07-13 13:53 ` Ian Campbell
2015-07-14 10:33 ` Yang Hongyang
2015-07-14 10:35 ` Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 27/28] tools/libxc: Drop all XG_LIBXL_HVM_COMPAT code from libxc Andrew Cooper
2015-07-13 12:01 ` [PATCH v3 28/28] tools/libxl: Drop all knowledge of toolstack callbacks Andrew Cooper
2015-07-13 15:55 ` Ian Jackson
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