Commit 61093179 authored by Léo Grange's avatar Léo Grange
Browse files

add mem_area_resize() with ability to remove unused pages

parent 100dfe86

sys/mem_area.c

+32 −0
Original line number Diff line number Diff line
@@ -106,6 +106,38 @@ int mem_area_insert(struct process *proc, struct mem_area *area) { 
}





int mem_area_resize(struct mem_area *area, size_t new_size, struct process *proc) {

	int ret = 0;

	size_t old_size = area->max_size;



	// first, call area-specific resize callback if any

	if(area->ops != NULL && area->ops->area_resize != NULL)

		ret = area->ops->area_resize(area, new_size);

	else

		area->max_size = new_size;



	new_size = area->max_size;



	// if no error occurs and decreasing the size of the area, release uneeded

	// pages

	if(ret == 0 && area->max_size < old_size) {

		void *old_last_page = MEM_PAGE_BEGINING(area->address + old_size);

		void *new_last_page = MEM_PAGE_BEGINING(area->address + new_size);

		union pm_page *page;

		

		for( ; new_last_page < old_last_page; new_last_page += 1024) {

			printk(LOG_DEBUG, "mem_area: release page @%p\n", new_last_page);



			page = mem_find_page(proc->dir_list, new_last_page);

			if(page != NULL) {

				mem_release_page(page);

			}

		}

	}



	return ret;

}





size_t mem_area_fill_partial_page(struct mem_area *area, size_t offset, void *dest) {

	size_t readsize = PM_PAGE_BYTES;

sys/mem_area.h

+12 −2
Original line number Diff line number Diff line
@@ -88,7 +88,7 @@ struct mem_area_ops { 
	 * Any page which is out of the area after decreasing size will be removed

	 * from the corresponding process address space by the caller.

	 */

	int (*area_resize)(struct mem_area *area, const struct mem_area *new_area);

	int (*area_resize)(struct mem_area *area, size_t new_size);

	



	/**
@@ -136,7 +136,7 @@ int mem_area_insert(struct process *proc, struct mem_area *area); 




/**

 * Generic function call when a page fault occurs, inside a given area address

 * Generic function called when a page fault occurs, inside a given area address

 * range.

 * The implementation specific operation is called to set the corresponding page.

 */
@@ -152,6 +152,16 @@ extern inline union pm_page mem_area_pagefault(struct mem_area *area, 
	}

}



/**

 * Resize an area to the given new_size.

 * If size is decreased and some memory pages associated with corresponding

 * process are excluded of the given area, each one is released.

 * TODO the design is not so good, process should be implicit?

 * Return 0 for success, negative value else.

 */

int mem_area_resize(struct mem_area *area, size_t new_size, struct process *proc);





/**

 * Helper for filesystem implementations, to handle MEM_AREA_PARTIAL.

 * Check for a given page to fill with 0 when needed, and return the number of

sys/memory.h

+5 −0
Original line number Diff line number Diff line
@@ -55,6 +55,11 @@ union pm_page { 
	( ((uint32)(addr) >> (PM_PAGE_ORDER)) & (MEM_DIRECTORY_PAGES - 1))





// get the first byte's address of the physical page of the given address

#define MEM_PAGE_BEGINING(addr) \

	(void*)((uint32)(addr) & ~(PM_PAGE_BYTES-1))





/**

 * Process address space is managed by a linked list of "pages directory".

 * Each directory describe a set of sequential virtual pages, and the virtual

sys/process.c

+4 −47
Original line number Diff line number Diff line
@@ -574,55 +574,12 @@ void *sys_sbrk(int incr) { 
	

	// heap area exists (maybe just created)

	if(heap != NULL) {

		void *ret;



		ret = heap->address;

		void *ret = heap->address;

		size_t new_size;



		printk(LOG_DEBUG, "sbrk: incr=%d\n", incr);



		// add or remove the given size

		if(incr > 0) {

			// just resize the heap area, allocation is done on page fault

			// FIXME need a check to ensure no area are overlayed by the heap!

			heap->max_size += incr;

		}



		else if(incr < 0) {

			// remove pages if possible

			int curalign;

			void *current_brk;



			// impossible to reduce the size beyond the original heap begin addr

			current_brk = heap->address + heap->max_size;

			incr = heap->max_size > -incr ? incr : -(heap->max_size);



			curalign = (((unsigned int) current_brk) - 1) % PM_PAGE_BYTES;

			if(curalign + incr < 0 ) {

				union pm_page *page;

				void *curvm;

				int nbpages;



				nbpages = (-incr - ((unsigned int)(current_brk) % PM_PAGE_BYTES)

						-1) / PM_PAGE_BYTES + 1;

				curvm = current_brk - ((unsigned int)(current_brk)

						% PM_PAGE_BYTES);



				while(nbpages > 0) {

					printk(LOG_DEBUG, "sbrk: remove page @%p\n", curvm);



					page = mem_find_page(cur->dir_list, curvm);

					if(page != NULL) {

						mem_release_page(page);

					}



					nbpages--;

					curvm -= PM_PAGE_BYTES;

				}

			}



			// resize heap memory area

			heap->max_size += incr;

		}

		new_size = -incr > heap->max_size ? 0 : heap->max_size + incr;

		mem_area_resize(heap, new_size, cur);



		return ret;

	}