[lttng-dev] [RFC Patch Ust 2/5] Serialize the CTF global structures for ust-comm

Mathieu Desnoyers mathieu.desnoyers at efficios.com
Fri May 2 05:29:09 EDT 2014


----- Original Message -----
> From: "Geneviève Bastien" <gbastien+lttng at versatic.net>
> To: "Mathieu Desnoyers" <mathieu.desnoyers at efficios.com>
> Cc: lttng-dev at lists.lttng.org
> Sent: Wednesday, April 30, 2014 9:05:35 PM
> Subject: Re: [lttng-dev] [RFC Patch Ust 2/5] Serialize the CTF global structures for ust-comm
> 
> On 14-04-27 04:34 AM, Mathieu Desnoyers wrote:
> > ----- Original Message -----
> >> From: "Geneviève Bastien" <gbastien+lttng at versatic.net>
> >> To: "Mathieu Desnoyers" <mathieu.desnoyers at efficios.com>
> >> Cc: lttng-dev at lists.lttng.org
> >> Sent: Wednesday, April 9, 2014 7:33:06 PM
> >> Subject: Re: [lttng-dev] [RFC Patch Ust 2/5] Serialize the CTF global
> >> structures for ust-comm
> >>
> >> On 04/09/2014 11:42 AM, Mathieu Desnoyers wrote:
> >>> ----- Original Message -----
> >>>> From: "Geneviève Bastien" <gbastien+lttng at versatic.net>
> >>>> To: lttng-dev at lists.lttng.org
> >>>> Sent: Wednesday, March 26, 2014 10:47:09 AM
> >>>> Subject: [lttng-dev] [RFC Patch Ust 2/5] Serialize the CTF global
> >>>> structures	for ust-comm
> >>>>
> >>>> It flatten the global types so that global types used by other global
> >>>> types
> >>> flatten -> flattens
> >>>
> >>>> all belong to the event at serialization. This avoids recursive calls to
> >>>> the
> >>>> send and receive functions and simplifies error handling (no recursive
> >>>> frees).
> >>> Is the structure and enum part of the event, or declared outside of
> >>> the event scope ?
> >> They are named structures so declared outside the scope of the event.
> >> But they are sent only if one event needs them.
> >>> Is there a downside to this approach ? For instance, if the same
> >>> structure is used in many events, do we have to send the structure info
> >>> many times ?
> >> Sending each structure (and enum) once would be enough, we could keep a
> >> hash table of global types that were sent, like we do before dumping the
> >> metadata of those global types, and that would avoid sending them many
> >> times. But it is not what is being done right now. We just send all the
> >> global types, but they are added to the metadata only once.
> > Repeating the integers, strings, etc on the "wire" (unix socket) for
> > every field between UST and sessiond was not so bad, since they were
> > small enough descriptions.
> >
> > However, I figure that enumerations, structures and variant types will
> > grow to be much larger than their basic types counterparts.
> >
> > Therefore, sending the global type separately, and then sending a
> > reference to that type (a string) when encountering the event field
> > using this global type seems like a more scalable solution to me.
> Just to be clear. Your comment is about the number of times a global
> type is sent across the wire, not the way it is sent in the current
> implementation (an event is followed by the global types it uses)? So
> that event1 which uses struct1 will have 1 global type following it and
> later on, when event2 using also struct1 is sent, then it will have 0
> global types, right?

Yes, all this is about not repeating global type descriptions over the
unix socket between applications and session daemon.

The issue here is that with the current approach, we have to repeat
possibly very long descriptions of structures, variants, and enums
because they need to be bundled after every event description.

Here is what I would envision instead:

- We add a "global type" notifier to the UST notfiers (there is currently
  only "event" and "channel"). Those notifier are sending the descriptions
  of channels and events as seen from within the application to
  lttng-sessiond, so it can put it in its ust registry to later generate
  the metadata,
- Those notifiers can be used to send descriptions of enums, structs, and
  variants,
- We'll probably want to have some way of verifying if the global
  type is exactly the same as global types with the same provider and
  global type names registered previously, thus dealing with different
  provider .so versions, each containing different versions of the global
  type. We'll have to find out what's the behavior when this check does
  not succeed (failure or versioning of the global type within sessiond ?).
  This verification will be needed once per global type, per application
  process. This verification needs to be done by sending the provider and
  global type name, along with the global type details (to see if it
  matches).
- Per global type, per application, we can keep a flag that knows whether
  the global type description has been successfully sent to the session
  daemon for each session.

Thanks,

Mathieu

> 
> I'll see what I can do, probably something similar to what is done for
> the events.
> 
> Thanks,
> 
> Geneviève
> >
> > Thanks,
> >
> > Mathieu
> >
> >> Thanks,
> >> Geneviève
> >>> Thanks,
> >>>
> >>> Mathieu
> >>>
> >>>> Signed-off-by: Geneviève Bastien <gbastien+lttng at versatic.net>
> >>>> ---
> >>>>    liblttng-ust-comm/lttng-ust-comm.c | 170
> >>>>    +++++++++++++++++++++++++++++++++----
> >>>>    liblttng-ust-ctl/ustctl.c          |  26 ++++++
> >>>>    2 files changed, 179 insertions(+), 17 deletions(-)
> >>>>
> >>>> diff --git a/liblttng-ust-comm/lttng-ust-comm.c
> >>>> b/liblttng-ust-comm/lttng-ust-comm.c
> >>>> index bc22130..90274c4 100644
> >>>> --- a/liblttng-ust-comm/lttng-ust-comm.c
> >>>> +++ b/liblttng-ust-comm/lttng-ust-comm.c
> >>>> @@ -742,6 +742,7 @@ int serialize_basic_type(enum ustctl_abstract_types
> >>>> *uatype,
> >>>>    	}
> >>>>    	case atype_array:
> >>>>    	case atype_sequence:
> >>>> +	case atype_structure:
> >>>>    	default:
> >>>>    		return -EINVAL;
> >>>>    	}
> >>>> @@ -800,6 +801,14 @@ int serialize_one_type(struct ustctl_type *ut,
> >>>> const
> >>>> struct lttng_type *lt)
> >>>>    		ut->atype = ustctl_atype_sequence;
> >>>>    		break;
> >>>>    	}
> >>>> +	case atype_structure:
> >>>> +	{
> >>>> +		strncpy(ut->u.structure.name, lt->u.structure.name,
> >>>> +						LTTNG_UST_SYM_NAME_LEN);
> >>>> +		ut->u.structure.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
> >>>> +		ut->atype = ustctl_atype_structure;
> >>>> +		break;
> >>>> +	}
> >>>>    	default:
> >>>>    		return -EINVAL;
> >>>>    	}
> >>>> @@ -892,25 +901,82 @@ int serialize_enum(struct ustctl_enum *uenum,
> >>>>    }
> >>>>    
> >>>>    static
> >>>> -int serialize_global_type_decl(size_t *_nr_write_global_type_decl,
> >>>> -		struct ustctl_global_type_decl **ustctl_global_type,
> >>>> +int serialize_structure(struct ustctl_structure *ustruct,
> >>>> +		const struct lttng_structure *lstruct)
> >>>> +{
> >>>> +	int ret;
> >>>> +
> >>>> +	strncpy(ustruct->name, lstruct->name, LTTNG_UST_SYM_NAME_LEN);
> >>>> +	ustruct->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
> >>>> +
> >>>> +	/* Serialize the fields */
> >>>> +	if (lstruct->nr_fields > 0) {
> >>>> +		ret = serialize_fields(&ustruct->nr_fields, &ustruct->fields,
> >>>> +				lstruct->nr_fields,	lstruct->fields);
> >>>> +		if (ret) {
> >>>> +			return ret;
> >>>> +		}
> >>>> +	}
> >>>> +
> >>>> +	return 0;
> >>>> +}
> >>>> +
> >>>> +static size_t get_child_global_type_count(size_t nr_global_type_decl,
> >>>> +		const struct lttng_global_type_decl *lttng_global_type)
> >>>> +{
> >>>> +	size_t total_global_types = 0;
> >>>> +	int i;
> >>>> +	const struct lttng_global_type_decl *lg;
> >>>> +
> >>>> +	for (i = 0; i < nr_global_type_decl; i++) {
> >>>> +		lg = &lttng_global_type[i];
> >>>> +
> >>>> +		if (lg->nowrite)
> >>>> +			continue;
> >>>> +
> >>>> +		/* Count the global types in children as well */
> >>>> +		switch (lg->mtype) {
> >>>> +		case mtype_structure:
> >>>> +		{
> >>>> +			const struct lttng_structure *ls;
> >>>> +
> >>>> +			ls = lg->u.ctf_structure;
> >>>> +			/* Add the number of global types it contains and the count of its
> >>>> own
> >>>> children */
> >>>> +			if (ls->nr_global_type_decl > 0) {
> >>>> +				total_global_types += ls->nr_global_type_decl;
> >>>> +				total_global_types +=
> >>>> get_child_global_type_count(ls->nr_global_type_decl,
> >>>> +								ls->global_type_decl);
> >>>> +			}
> >>>> +			break;
> >>>> +		}
> >>>> +		case mtype_enum:
> >>>> +		default:
> >>>> +			break;
> >>>> +		}
> >>>> +	}
> >>>> +
> >>>> +	return total_global_types;
> >>>> +}
> >>>> +
> >>>> +/*
> >>>> + * When this method is called, index is the next index to write to and
> >>>> the
> >>>> + * ustctl_global_type structure is already initialized and will not
> >>>> overflow.
> >>>> + *
> >>>> + * The global type declarations are flattened at serialization to avoid
> >>>> + * needing to do recursive frees on error.
> >>>> + */
> >>>> +static int _serialize_global_type_decl(size_t *index,
> >>>> +		struct ustctl_global_type_decl *global_type_decl,
> >>>>    		size_t nr_global_type_decl,
> >>>>    		const struct lttng_global_type_decl *lttng_global_type)
> >>>>    {
> >>>> -	struct ustctl_global_type_decl *global_type_decl;
> >>>>    	int i, ret;
> >>>> -	size_t nr_write_global_type_decl = 0;
> >>>> -
> >>>> -	global_type_decl = zmalloc(nr_global_type_decl
> >>>> -					* sizeof(*global_type_decl));
> >>>> -	if (!global_type_decl)
> >>>> -		return -ENOMEM;
> >>>>    
> >>>>    	for (i = 0; i < nr_global_type_decl; i++) {
> >>>>    		struct ustctl_global_type_decl *f;
> >>>>    		const struct lttng_global_type_decl *lf;
> >>>>    
> >>>> -		f = &global_type_decl[nr_write_global_type_decl];
> >>>> +		f = &global_type_decl[*index];
> >>>>    		lf = &lttng_global_type[i];
> >>>>    
> >>>>    		/* skip 'nowrite' fields */
> >>>> @@ -928,18 +994,66 @@ int serialize_global_type_decl(size_t
> >>>> *_nr_write_global_type_decl,
> >>>>    			le = lf->u.ctf_enum;
> >>>>    			ret = serialize_enum(ue, le);
> >>>>    			if (ret)
> >>>> -				goto error;
> >>>> +				return ret;
> >>>>    
> >>>>    			f->mtype = ustctl_mtype_enum;
> >>>>    			break;
> >>>>    		}
> >>>> +		case mtype_structure:
> >>>> +		{
> >>>> +			struct ustctl_structure *us;
> >>>> +			const struct lttng_structure *ls;
> >>>> +
> >>>> +			/* Serialize children global types first */
> >>>> +			ls = lf->u.ctf_structure;
> >>>> +			ret = _serialize_global_type_decl(index,
> >>>> +					global_type_decl,
> >>>> +					ls->nr_global_type_decl,
> >>>> +					ls->global_type_decl);
> >>>> +			if (ret)
> >>>> +				return ret;
> >>>> +
> >>>> +			/* Reinitialize f since the index may have changed */
> >>>> +			f = &global_type_decl[*index];
> >>>> +			us = &f->u.ctf_structure;
> >>>> +
> >>>> +			ret = serialize_structure(us, ls);
> >>>> +			if (ret)
> >>>> +				return ret;
> >>>> +
> >>>> +			f->mtype = ustctl_mtype_structure;
> >>>> +			break;
> >>>> +		}
> >>>>    		default:
> >>>> -			ret = -EINVAL;
> >>>> -			goto error;
> >>>> +			return -EINVAL;
> >>>>    		}
> >>>>    
> >>>> -		nr_write_global_type_decl++;
> >>>> +		*index = *index + 1;
> >>>>    	}
> >>>> +	return 0;
> >>>> +}
> >>>> +
> >>>> +static
> >>>> +int serialize_global_type_decl(size_t *_nr_write_global_type_decl,
> >>>> +		struct ustctl_global_type_decl **ustctl_global_type,
> >>>> +		size_t nr_global_type_decl,
> >>>> +		const struct lttng_global_type_decl *lttng_global_type)
> >>>> +{
> >>>> +	struct ustctl_global_type_decl *global_type_decl;
> >>>> +	int i, ret;
> >>>> +	size_t nr_write_global_type_decl = 0;
> >>>> +	size_t nr_child_global_type_cnt =
> >>>> get_child_global_type_count(nr_global_type_decl,
> >>>> +							lttng_global_type);
> >>>> +
> >>>> +	global_type_decl = zmalloc((nr_global_type_decl +
> >>>> nr_child_global_type_cnt)
> >>>> +					* sizeof(*global_type_decl));
> >>>> +	if (!global_type_decl)
> >>>> +		return -ENOMEM;
> >>>> +
> >>>> +	ret = _serialize_global_type_decl(&nr_write_global_type_decl,
> >>>> global_type_decl,
> >>>> +			nr_global_type_decl, lttng_global_type);
> >>>> +	if (ret)
> >>>> +		goto error;
> >>>>    
> >>>>    	*_nr_write_global_type_decl = nr_write_global_type_decl;
> >>>>    	*ustctl_global_type = global_type_decl;
> >>>> @@ -954,6 +1068,9 @@ error:
> >>>>    		case ustctl_mtype_enum:
> >>>>    			free(m->u.ctf_enum.entries);
> >>>>    			break;
> >>>> +		case ustctl_mtype_structure:
> >>>> +			free(m->u.ctf_structure.fields);
> >>>> +			break;
> >>>>    		default:
> >>>>    			break;
> >>>>    		}
> >>>> @@ -1158,15 +1275,31 @@ int ustcomm_register_event(int sock,
> >>>>    				}
> >>>>    				break;
> >>>>    			}
> >>>> +			case ustctl_mtype_structure:
> >>>> +			{
> >>>> +				int field_len = one_global_type->u.ctf_structure.nr_fields *
> >>>> sizeof(*one_global_type->u.ctf_structure.fields);
> >>>> +
> >>>> +				/* Send the fields */
> >>>> +				DBG("Sending fields for global type structure %s.\n",
> >>>> +						one_global_type->u.ctf_structure.name);
> >>>> +				len = ustcomm_send_unix_sock(sock,
> >>>> one_global_type->u.ctf_structure.fields, field_len);
> >>>> +				free(one_global_type->u.ctf_structure.fields);
> >>>> +				one_global_type->u.ctf_structure.fields = NULL;
> >>>> +				if (len > 0 && len != field_len) {
> >>>> +					goto error_global_type;
> >>>> +				}
> >>>> +				if (len < 0) {
> >>>> +					goto error_global_type;
> >>>> +				}
> >>>> +				break;
> >>>> +			}
> >>>>    			default:
> >>>>    				break;
> >>>>    			}
> >>>>    		}
> >>>> -		free(global_type_decl);
> >>>>    
> >>>> -	} else {
> >>>> -		free(global_type_decl);
> >>>>    	}
> >>>> +	free(global_type_decl);
> >>>>    
> >>>>    	/* receive reply */
> >>>>    	len = ustcomm_recv_unix_sock(sock, &reply, sizeof(reply));
> >>>> @@ -1212,6 +1345,9 @@ error_global_type:
> >>>>    		case ustctl_mtype_enum:
> >>>>    			free(one_global_type->u.ctf_enum.entries);
> >>>>    			break;
> >>>> +		case ustctl_mtype_structure:
> >>>> +			free(one_global_type->u.ctf_structure.fields);
> >>>> +			break;
> >>>>    		default:
> >>>>    			break;
> >>>>    		}
> >>>> diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
> >>>> index a181e62..3100f1b 100644
> >>>> --- a/liblttng-ust-ctl/ustctl.c
> >>>> +++ b/liblttng-ust-ctl/ustctl.c
> >>>> @@ -1896,6 +1896,32 @@ int ustctl_recv_register_event(int sock,
> >>>>    				}
> >>>>    				break;
> >>>>    			}
> >>>> +			case ustctl_mtype_structure:
> >>>> +			{
> >>>> +				int entry_len = one_global_type->u.ctf_structure.nr_fields *
> >>>> sizeof(*one_global_type->u.ctf_structure.fields);
> >>>> +				/* Receive the entries */
> >>>> +				one_global_type->u.ctf_structure.fields = zmalloc(entry_len);
> >>>> +				if (!one_global_type->u.ctf_structure.fields) {
> >>>> +					len = -ENOMEM;
> >>>> +					goto global_type_error;
> >>>> +				}
> >>>> +				len = ustcomm_recv_unix_sock(sock,
> >>>> +						one_global_type->u.ctf_structure.fields,
> >>>> +						entry_len);
> >>>> +				DBG("Received fields for struct %s.\n",
> >>>> one_global_type->u.ctf_structure.name);
> >>>> +				if (len > 0 && len != entry_len) {
> >>>> +					len = -EIO;
> >>>> +					goto global_type_error;
> >>>> +				}
> >>>> +				if (len == 0) {
> >>>> +					len = -EPIPE;
> >>>> +					goto global_type_error;
> >>>> +				}
> >>>> +				if (len < 0) {
> >>>> +					goto global_type_error;
> >>>> +				}
> >>>> +				break;
> >>>> +			}
> >>>>    			default:
> >>>>    				break;
> >>>>    			}
> >>>> --
> >>>> 1.9.1
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> lttng-dev mailing list
> >>>> lttng-dev at lists.lttng.org
> >>>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
> >>>>
> >>
> 
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com



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