Commit 8a4c2495 authored by Alexey Korolev's avatar Alexey Korolev Committed by David Woodhouse
Browse files

MTD: nandsim: use less RAM 



Nandsim consumes ~2x more RAM than the density of simulated device.
It becomes critical if we need to simulate 256MB NAND and run stress tests
on it.

We investigated the reasons. nandsim allocates space for pages using kmalloc
function. The size of LP nand page is 2112 bytes.
kmalloc gets space from slab pools by chunks 2^n. So if we need to kmalloc
2112 bytes, 4096 bytes will be consumed by system.
The best way to avoid this issue would be using kmem_cache allocations. AFAIK
this mechanism specially designed to handle cases when arrays of allocations
are used.

Signed-off-by: default avatarAlexey Korolev <akorolev@infradead.org>
Tested-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: default avatarArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: default avatarDavid Woodhouse <David.Woodhouse@intel.com>
parent a9fc8991

drivers/mtd/nand/nandsim.c

+18 −7
Original line number Diff line number Diff line
@@ -303,6 +303,9 @@ struct nandsim { 
	/* The simulated NAND flash pages array */

	union ns_mem *pages;



	/* Slab allocator for nand pages */

	struct kmem_cache *nand_pages_slab;



	/* Internal buffer of page + OOB size bytes */

	union ns_mem buf;
@@ -435,8 +438,8 @@ static struct mtd_info *nsmtd; 
static u_char ns_verify_buf[NS_LARGEST_PAGE_SIZE];



/*

 * Allocate array of page pointers and initialize the array to NULL

 * pointers.

 * Allocate array of page pointers, create slab allocation for an array

 * and initialize the array by NULL pointers.

 *

 * RETURNS: 0 if success, -ENOMEM if memory alloc fails.

 */
@@ -484,6 +487,12 @@ static int alloc_device(struct nandsim *ns) 
	for (i = 0; i < ns->geom.pgnum; i++) {

		ns->pages[i].byte = NULL;

	}

	ns->nand_pages_slab = kmem_cache_create("nandsim",

						ns->geom.pgszoob, 0, 0, NULL);

	if (!ns->nand_pages_slab) {

		NS_ERR("cache_create: unable to create kmem_cache\n");

		return -ENOMEM;

	}



	return 0;
@@ -511,8 +520,10 @@ static void free_device(struct nandsim *ns) 
	if (ns->pages) {

		for (i = 0; i < ns->geom.pgnum; i++) {

			if (ns->pages[i].byte)

				kfree(ns->pages[i].byte);

				kmem_cache_free(ns->nand_pages_slab,

						ns->pages[i].byte);

		}

		kmem_cache_destroy(ns->nand_pages_slab);

		vfree(ns->pages);

	}

}
@@ -1475,7 +1486,7 @@ static void erase_sector(struct nandsim *ns) 
	for (i = 0; i < ns->geom.pgsec; i++) {

		if (mypage->byte != NULL) {

			NS_DBG("erase_sector: freeing page %d\n", ns->regs.row+i);

			kfree(mypage->byte);

			kmem_cache_free(ns->nand_pages_slab, mypage->byte);

			mypage->byte = NULL;

		}

		mypage++;
@@ -1538,10 +1549,10 @@ static int prog_page(struct nandsim *ns, int num) 
		/*

		 * We allocate memory with GFP_NOFS because a flash FS may

		 * utilize this. If it is holding an FS lock, then gets here,

		 * then kmalloc runs writeback which goes to the FS again

		 * and deadlocks. This was seen in practice.

		 * then kernel memory alloc runs writeback which goes to the FS

		 * again and deadlocks. This was seen in practice.

		 */

		mypage->byte = kmalloc(ns->geom.pgszoob, GFP_NOFS);

		mypage->byte = kmem_cache_alloc(ns->nand_pages_slab, GFP_NOFS);

		if (mypage->byte == NULL) {

			NS_ERR("prog_page: error allocating memory for page %d\n", ns->regs.row);

			return -1;

CRA Git | Maintained and supported by SUSTech CRA and CCSE