<br><br><div class="gmail_quote">2012/5/7 Gedare Bloom <span dir="ltr"><<a href="mailto:gedare@rtems.org" target="_blank">gedare@rtems.org</a>></span><br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>On Mon, May 7, 2012 at 11:16 AM, Ashi <<a href="mailto:ashi08104@gmail.com" target="_blank">ashi08104@gmail.com</a>> wrote:<br>
> I'm terribly sorry for my late reply. I'm off for my weekend.<br>
><br>
</div>Most of us are. :)<br>
<div><div><br>
> 2012/5/4 Gedare Bloom <<a href="mailto:gedare@rtems.org" target="_blank">gedare@rtems.org</a>><br>
>><br>
>> On Fri, May 4, 2012 at 3:28 AM, Ashi <<a href="mailto:ashi08104@gmail.com" target="_blank">ashi08104@gmail.com</a>> wrote:<br>
>> > Hi, all. I'm working on the "Use hash or map in POSIX keys" project.<br>
>> > As Joel said, the first thing to be determined is the problem of what<br>
>> > data goes with each thread and what goes with each key. I find it's<br>
>> > difficult to design the interface without some specific approach. And<br>
>> > since the rbtree api is available in RTEMS, I have tried to do the<br>
>> > design in the rbtree approach.<br>
>> ><br>
>> Good. The rbtree should support an efficient map operation.<br>
>><br>
> Gedare, thanks for your reply!<br>
><br>
>><br>
>> > I find 2 data structures need revised(added): POSIX_Keys_Control and<br>
>> > key_node.<br>
>> ><br>
>> > typedef struct {<br>
>> > Objects_Control Object;<br>
>> > void (*destructor)( void * );<br>
>> > key_node * key_node_ptr;<br>
>> > }POSIX_Keys_Control;<br>
>> ><br>
>> > typedef struct{<br>
>> > rtems_rbtree_node Node;<br>
>> > Objects_Id thread_id;<br>
>> > void **value;<br>
>> > }key_node;<br>
>> ><br>
>> > POSIX_Keys_Control is used to manage all keys. And key_node is the<br>
>> > structure contains key data and rbtree node.<br>
>> I think you might want an rtems_rbtree_control key_tree field in<br>
>> POSIX_Keys_Control instead of this key_node* dynamic array. Then your<br>
>> code can add structs containing an rtems_rbtree_node dynamically to<br>
>> the key_tree.<br>
><br>
> After read the rbtree.h in score, I find I confused the rtems_rbtree_node<br>
> and rtems_rbtree_control. It should be the rtems_rbtree_control here.<br>
><br>
>> Also the key_node structure should follow a naming convention of<br>
>> POSIX_Keys_Key_node or something similar.<br>
>> API_Package_name_Struct_type_name is the general format for<br>
>> structures. API_Package_name_Method_name is the general format for<br>
>> functions. Note the mixture of lower and upper case letters.<br>
><br>
> I see.<br>
><br>
>><br>
>> > I'm not quite sure about the Objects_Control member's function in<br>
>> > current implementation. I find key = Object.id, in which key is<br>
>> > pthread_key_t type, and _POSIX_Keys_Get(key, &location) is used to<br>
>> > find key's corresponding the_key, which is POSIX_Keys_Control type.So<br>
>> > is it the only function of Object member ?<br>
>> ><br>
>> Object_Control means the structure embeds an RTEMS Object so that the<br>
>> structure can be managed by the Object Manager whose responsibilities<br>
>> include pre-allocating enough objects of a certain type to satisfy<br>
>> requests to Create those objects.<br>
>><br>
>> It seems to me that the Key (key_node) should be the Object since the<br>
>> number of keys is the resource being managed. The present solution<br>
>> uses an array of values (one for each thread) because each thread can<br>
>> have its own version of a given key. The key is "looked up" by the<br>
>> Object Id of the Key and then the requesting thread. What we should<br>
>> prefer is a more scalable solution that does not require<br>
>> pre-allocating an array of values for all possible threads. Something<br>
>> like...<br>
>> typedef struct {<br>
>> Objects_Control Object;<br>
>> void (*destructor)( void * );<br>
>> rtems_rbtree_node Node;<br>
>> Objects_Id thread_id;<br>
>> void **value;<br>
>> } POSIX_Keys_Control;<br>
>><br>
>> And maybe a global:<br>
>> rtems_rbtree_control POSIX_Keys_Tree;<br>
><br>
><br>
> I think this is a new and great idea that I haven't thought before,Does it<br>
> mean a single POSIX_Keys_Tree contains all node in the system?<br>
</div></div>yes<br>
<div><br>
> I know a rbtree contains only key data belongs to one specific key in my<br>
> design above, and I was thinking the idea of manage all keys by a rbtree,<br>
> then there would be a hiearchy: all keys are in one rbtree, and each key's<br>
> data are in their own rbtrees. But I think this design is a little complex,<br>
> and your idea is more uniform. However, will these two differ much in<br>
> runtime?<br>
><br>
</div>not sure because i do not quite understand your design. but I get the<br>
feeling that your design will have a big problem of managing multiple<br>
rbtrees simultaneously. I have not tried to do that before. Both<br>
approaches seem like they would have similar (log-time) asymptotic<br>
behavior.<br>
<div><div><br></div></div></blockquote><div>I mean all keys are managed in one globle rbtree, in which each node has a member of rtems_rbtree_control, like:<br>typedef struct {<br><div style="margin-left:40px">Objects_Control Object;<br>
void (*destructor)(void*);<br>rtems_rbtree_node Node;<br>rtems_rbtree_control key_tree;<br></div>}POSIX_Keys_Control;<br><br>and for each key, all the key data is managed in each key's rbtree, like:<br>typedef struct{<br>
<div style="margin-left:40px">rtems_rbtree_node node;<br>Objects_Id thread_id;<br>void *value;<br></div>}POSIX_Keys_Key_node;<br>However, this design seems more complex. And I don't know what could lead to the problem of managing multiple<br>
rbtrees simultaneously, can you give some example?<br><br>-zw_yao<br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div><div>
>><br>
>> Then you would implement an rbtree_compare function that will combine<br>
>> the <a href="http://POSIX_Keys_control.Object.id" target="_blank">POSIX_Keys_control.Object.id</a> with POSIX_Keys_control.thread_id as<br>
>> a "key" for the rbtree to use for storing each POSIX_Keys_Control.<br>
>><br>
> I see, I can compare <a href="http://POSIX_Keys_control.Object.id" target="_blank">POSIX_Keys_control.Object.id</a> first and if they are<br>
> equal, then compare the POSIX_Keys_control.thread_id.<br>
><br>
><br>
>> all key related operations are described as follow:<br>
>> - key create:<br>
>> create POSIX_Keys_Control instance and intialize an empty rbtree, in<br>
>> which rtems_rbtree_control instance will be created and an rbtree<br>
>> node's key compare function is also needed. Thread_id is compared in<br>
>> the compare function. So this approach doesdn't consider allocate same<br>
>> data for the same thread in the same key, because only different<br>
>> Thread_id are comparable. But I find something about duplicate node in<br>
>> the Gedare's rbtree patch, maybe the duplicate feature also can be<br>
>> added into POSIX key.<br>
>><br>
>><br>
>> You still want unique rbtree comparisons so that a thread can<br>
>> distinguish its own keys, unless it is valid for a thread to allocate<br>
>> multiple values with the same key?<br>
>><br>
>> Key create should not create the red-black tree; the rbtree should be<br>
>> created during initialization of the POSIX_Keys manager---which by the<br>
>> way is improperly named right now as POSIX_Key_Manager_initialization<br>
>> and should be renamed POSIX_Keys_Manager_initialization with an s on<br>
>> Keys (or just POSIX_Keys_Initialization).<br>
>><br>
> I didn't notice the POSIX_Key_Manager_initialization before, thanks. BTW<br>
> I've a question about the _Objects_Initialize_information(), which<br>
> _POSIX_Key_Manager_initialization calls. I read the code of<br>
> _Objects_Initialize_information(), but still don't know what the maximum<br>
> parameter is used for? I think it's not for determining the memory size of<br>
> all objects in one manager and then allocating such size of memory, is it?<br>
><br>
</div></div>maximum determines the total number of that kind of object. it is<br>
controlled by some CONFIGURE_MAXIMUM_XXX, e.g.<br>
CONIFIGURE_MAXIMUM_POSIX_KEYS.<br>
<span><font color="#888888"><br>
-Gedare<br>
</font></span><div><div><br>
>> > - key delete<br>
>> > delete all the nodes in rbtree by rtems_rbtree_get_min() or<br>
>> > rtems_rbtree_get_max(), and delete the RBTree_Control,<br>
>> > POSIX_Keys_Control instance. The key data's deallocation is done by<br>
>> > user.<br>
>> ><br>
>> > - key get specific<br>
>> > we can use _RBTree_Find() to do the actually work behind<br>
>> > get_specific(), the runtime is O(log(n))<br>
>> ><br>
>> > - key set specific<br>
>> > after a proper key_node is create, we can use _RBTree_Insert() to do<br>
>> > the set specific. the runtime is rbtree insert runtime, which is<br>
>> > O(log(n)).<br>
>> ><br>
>> > I'm not sure whether this design is appropriate and this design is<br>
>> > very simple, need many more work to do. Hope further discussion to<br>
>> > make it more clear!<br>
>> ><br>
>> Simple is good. I think you're on the right track other than my few<br>
>> comments about organizing the structures. You have the right ideas for<br>
>> how to implement the Keys functions I believe.<br>
>> -Gedare<br>
><br>
> Yeah, it remind me the K.I.S.S. principle!<br>
><br>
> -best regards!<br>
> -zw_yao<br>
>><br>
>><br>
>> > --best regards!<br>
>> > --zw_yao<br>
>> > _______________________________________________<br>
>> > rtems-devel mailing list<br>
>> > <a href="mailto:rtems-devel@rtems.org" target="_blank">rtems-devel@rtems.org</a><br>
>> > <a href="http://www.rtems.org/mailman/listinfo/rtems-devel" target="_blank">http://www.rtems.org/mailman/listinfo/rtems-devel</a><br>
><br>
><br>
</div></div></blockquote></div><br>