[PATCH] add freelist data structure to score
Ashi
ashi08104 at gmail.com
Thu Jul 11 04:25:50 UTC 2013
And I'm adding the test case, and find we haven't the SAPI for freelist
yet. I must add it before adding test case, right? By the way, is the SAPI
same as the user-level API layer as Gedare mentioned before? I haven't
realized it before.
On Wed, Jul 10, 2013 at 8:31 PM, Gedare Bloom <gedare at rtems.org> wrote:
> You would call extend instead of calling bump, or as part of bumping.
>
Thanks, I see.
>
> On Wed, Jul 10, 2013 at 2:30 AM, Ashi <ashi08104 at gmail.com> wrote:
> > Thanks for all good explanation.
> >
> >
> > On Tue, Jul 9, 2013 at 11:24 PM, Sebastian Huber
> > <sebastian.huber at embedded-brains.de> wrote:
> >>
> >> On 07/09/2013 05:29 AM, Ashi wrote:
> >>>
> >>> Hi, Sebastian, thanks for your review!
> >>>
> >>> 在 2013-7-7 下午9:49，"Sebastian Huber" <
> sebastian.huber at embedded-brains.de
> >>> <mailto:sebastian.huber at embedded-brains.de>>写道：
> >>>
> >>> >
> >>> > Hello Ashi,
> >>> >
> >>> >
> >>> > On 06/07/13 09:17, Ashi wrote:
> >>> >>
> >>> >> Hi all,
> >>> >>
> >>> >> this patch adds a data structure called freelist to score, there
> are
> >>> no
> >>> >> test cases yet and should be added later.
> >>> >
> >>> >
> >>> > I would appreciate to have the test for this new stuff included in
> the
> >>> patch.
> >>>
> >>>
> >>> sure, I will update the patch with test cases.
> >>> >
> >>> >
> >>> >>
> >>> >> Freelist is a structure, which contains a chain of nodes. It
> supports
> >>> 2
> >>> >> operation:
> >>> >> - get node from freelist
> >>> >> - put node to freelist.
> >>> >> And when there is no enough node in freelist, it will automatically
> >>> >> increase itself's size by allocate more nodes from heap or
> >>> workspace(which
> >>> >> is specified by user).
> >>> >
> >>> >
> >>> > What can I do if I like to get the nodes from a magic space?
> >>>
> >>>
> >>> sorry for the unclear, you can get nodes from freelist by 'get'
> >>> operation. And
> >>> if you mean get nodes from heap or workspace, it's done by
> >>> _Freelist_Get_node(), which calls _Freelist_Bump() when there is no
> free
> >>> node left.
> >>
> >>
> >> Yes, the problem is that you limit your Freelist to the heap and
> >> workspace. If you use a handler function (or virtual method if you
> like)
> >> then you can avoid this limitation.
> >>
> >> [...]
> >>
> >>> >> +/**
> >>> >> + * @typedef freelist_callout
> >>> >> + */
> >>> >> +typedef void (*freelist_callout)(
> >>> >> + Freelist_Control *fc,
> >>> >> + void *nodes
> >>> >> +);
> >>> >> +
> >>> >> +/**
> >>> >> + * @typedef Freelist_Control_struct
> >>> >> + *
> >>> >> + * This is used to manage each element.
> >>> >> + */
> >>> >> +struct Freelist_Control_struct {
> >>> >> + Chain_Control Freelist;
> >>> >> + size_t free_count;
> >>> >
> >>> >
> >>> > Why do we need the free_count?
> >>>
> >>> free_count is used to keep track how many nodes there is in freelist.
> And
> >>> if
> >>> free_count is 0 when you try to get node from freelist by call
> >>> _Freelist_Get_node(), _Freelist_Get_node() will call _Freelist_Bump()
> to
> >>> allocate more node from heap or workspace.
> >>
> >>
> >> The list knows if it is empty. There is not need to store this
> >> information in two ways.
> >>
> >>
> >>> >
> >>> >> + size_t bump_count;
> >>> >> + size_t node_size;
> >>> >
> >>> >
> >>> >> + freelist_callout callout;
> >>> >> + bool use_workspace;
> >>> >> +};
> >>> >
> >>> >
> >>> > I would replace this with an extend handler.
> >>> >
> >>> > /**
> >>> > * @brief Extends the freelist.
> >>> > *
> >>> > * @param[in] freelist The freelist control.
> >>> > *
> >>> > * @return The count of new nodes.
> >>> > */
> >>> > typedef size_t ( *Freelist_Extend )( Freelist_Control *freelist );
> >>> >
> >>> > This is much more flexible since you only specify the interface and
> >>> don't
> >>> limit this to heap/workspace.
> >>> >
> >>> > You can provide a _Freelist_Extend_with_nothing() which simply
> returns
> >>> 0.
> >>>
> >>> Yeah, this Freelist_Extend is very flexible, but I feel the
> >>> Freelist_Extend is
> >>> a little complex. As it shows in _Freelist_Bump(), if users provides
> >>> their own
> >>> extension function, they have to append there new nodes to freelist's
> >>> internal
> >>> chain and call their callout function on new nodes. And since
> >>> _Freelist_Initialize() also would call Freelist_Extend(), if we
> provided
> >>> _Freelist_Extend_with_nothing(), the initialization may fail.
> >>
> >>
> >> Since the Freelist_Extend gets the Freelist as a first argument it can
> set
> >> the extend handler to _Freelist_Extend_with_nothing() after the first
> >> invocation.
> >>
> >> Example:
> >>
> >>
> >> /**
> >> * @brief Extends the freelist.
> >> *
> >> * @param[in] freelist The freelist control.
> >> */
> >> typedef void ( *Freelist_Extend )( Freelist_Control *freelist );
> >>
> >> typedef struct {
> >> Objects_Control obj;
> >> int x;
> >> } my_obj;
> >>
> >> void my_extend( Freelist_Control *freelist )
> >> {
> >> size_t bump_count = freelist->bump_count;
> >> size_t size = bump_count * sizeof(my_obj);
> >> my_obj *objs = malloc(size);
> >>
> >> _Freelist_Set_extend_handler( freelist, _Freelist_Extend_with_nothing
> );
> >> _Chain_Initialize(
> >> _Freelist_Get_list( freelist ),
> >> objs,
> >> bump_count,
> >> size
> >> );
> >>
> >> }
> >
> > I'm a little confused by my_extend() function, is it only called after
> > calling _Freelist_Initialize() by user?
> >>
> >>
> >> [...]
> >>
> >> --
> >> Sebastian Huber, embedded brains GmbH
> >>
> >> Address : Dornierstr. 4, D-82178 Puchheim, Germany
> >> Phone : +49 89 189 47 41-16
> >> Fax : +49 89 189 47 41-09
> >> E-Mail : sebastian.huber at embedded-brains.de
> >> PGP : Public key available on request.
> >>
> >> Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
> >
> >
> > Cheers,
> > Zhongwei
> >
>
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