[PATCH] add freelist data structure to score
Ashi
ashi08104 at gmail.com
Fri Jul 12 10:57:44 UTC 2013
On Thu, Jul 11, 2013 at 9:18 PM, Gedare Bloom <gedare at rtems.org> wrote:
> I don't think we need SAPI. We could consider adding a "classic"
> manager interface. Meanwhile, you can write the testsuite with
> "#define __RTEMS_VIOLATE_KERNEL_VISIBILITY__" and access the supercore
> freelist interface directly...
>
OK, I'll use direct way for now.
>
> On Thu, Jul 11, 2013 at 12:25 AM, Ashi <ashi08104 at gmail.com> wrote:
> >
> > 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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