MTD: nandsim: use less RAM

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=8a4c2495b142fe612b291a810d9e695f269c26db
Commit:     8a4c2495b142fe612b291a810d9e695f269c26db
Parent:     a9fc8991883cdf029bd373a82cbc2d12a10799dd
Author:     Alexey Korolev <akorolev at infradead.org>
AuthorDate: Thu Nov 13 13:40:38 2008 +0000
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Wed Dec 10 13:35:23 2008 +0000

    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: Alexey Korolev <akorolev at infradead.org>
    Tested-by: Artem Bityutskiy <Artem.Bityutskiy at nokia.com>
    Acked-by: Artem Bityutskiy <Artem.Bityutskiy at nokia.com>
    Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy at nokia.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/nand/nandsim.c |   25 ++++++++++++++++++-------
 1 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index baa6f95..43ce26d 100644
--- a/drivers/mtd/nand/nandsim.c
+++ b/drivers/mtd/nand/nandsim.c
@@ -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;