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* About I/O callbacks ...
@ 2001-06-22  1:46 Davide Libenzi
  0 siblings, 0 replies; 6+ messages in thread
From: Davide Libenzi @ 2001-06-22  1:46 UTC (permalink / raw)
  To: linux-kernel


I was just thinking to implement I/O callbacks inside the kernel and test which
kind of performance could result compared to a select()/poll() implementation.
I prefer IO callbacks against async-io coz in this way is more direct to
implement an I/O driven state machine + coroutines.
This is a first draft :



#define ASCB_INFO_NPARAMS 4

struct ascb_info {
        unsigned long param[ASCB_INFO_NPARAMS];
};

struct iocb {
        struct iocb * next;
        struct task_struct * task;
        unsigned long event;
        int (*iocb_func)(struct ascb_info *, void *);
        void * data;
};

struct ascb {
        struct ascb * next;
        int (*ascb_func)(struct ascb_info *, void *);
        void * data;
        struct ascb_info info;
};





struct task_struct {
        ...
        struct ascb * ascb_list;
        spinlock_t ascb_list_lock;
        ...
};


struct file {
        ...
        struct iocb * iocb_list;
        spinlock_t iocb_list_lock;
        ...
};




The user call some user-space api to add the callback to the fd and this will
result ( inside the kernel ) to a call to :



int iocb_file_add(struct file * file,
                int (*iocb_func)(struct ascb_info *, void *), void * data,
                unsigned long event) {

/*
 *  Add the callback to the file list with task = current
 */


}



This is used to add callbacks to the task's list :

int ascb_task_add(struct task_struct * task,
                int (*ascb_func)(struct ascb_info *, void *),
                void * data, struct ascb_info * info) {

/*
 *  Add the callback to the task list
 */

}




Low level I/O layers will call this to dispatch I/O events :


int iocb_file_dispatch(struct file * file, unsigned long event) {

/*
 *  Scan the iocb_list and ( if event match ) call ascb_task_add()
 *  and remove ( y/n ? ) the callback from iocb_list
 */


}




In entry.S we'll have a call like do_signal() that will build the frame for a
callback call ( like do_signal() ) and will remove the entry from the list.
My first implementation should address only sockets but once the concept of
async callbacks is inside the task_struct this could be gradually extended to
std files and even used as an extension of signals.

Comments ?





- Davide



^ permalink raw reply	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2001-06-22 22:21 UTC | newest]

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     [not found] <XFMail.20010621184645.davidel@xmailserver.org.suse.lists.linux.kernel>
2001-06-22  7:49 ` About I/O callbacks Andi Kleen
2001-06-22 15:55   ` Davide Libenzi
2001-06-22 15:59     ` Andi Kleen
2001-06-22 16:07       ` Davide Libenzi
2001-06-22 22:23       ` Davide Libenzi
2001-06-22  1:46 Davide Libenzi

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