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Commit 8fb870df authored by David Woodhouse's avatar David Woodhouse
Browse files

[JFFS2] Trigger garbage collection when very_dirty_list size becomes excessive 



With huge amounts of free space, we weren't bothering to GC for while a
while, and pathological numbers of obsolete nodes were accumulating,
seriously affecting performance on NAND flash (OLPC trac #3978)

Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
parent 49defc01

fs/jffs2/build.c

+10 −0
Original line number Diff line number Diff line
@@ -285,6 +285,14 @@ static void jffs2_calc_trigger_levels(struct jffs2_sb_info *c) 
	   than actually making progress? */

	c->resv_blocks_gcbad = 0;//c->resv_blocks_deletion + 2;



	/* What number of 'very dirty' eraseblocks do we allow before we

	   trigger the GC thread even if we don't _need_ the space. When we

	   can't mark nodes obsolete on the medium, the old dirty nodes cause

	   performance problems because we have to inspect and discard them. */

	c->vdirty_blocks_gctrigger = c->resv_blocks_gcmerge;

	if (jffs2_can_mark_obsolete(c))

		c->vdirty_blocks_gctrigger *= 10;



	/* If there's less than this amount of dirty space, don't bother

	   trying to GC to make more space. It'll be a fruitless task */

	c->nospc_dirty_size = c->sector_size + (c->flash_size / 100);
@@ -303,6 +311,8 @@ static void jffs2_calc_trigger_levels(struct jffs2_sb_info *c) 
		  c->resv_blocks_gcbad, c->resv_blocks_gcbad*c->sector_size/1024);

	dbg_fsbuild("Amount of dirty space required to GC: %d bytes\n",

		  c->nospc_dirty_size);

	dbg_fsbuild("Very dirty blocks before GC triggered: %d\n",

		  c->vdirty_blocks_gctrigger);

}



int jffs2_do_mount_fs(struct jffs2_sb_info *c)

fs/jffs2/jffs2_fs_sb.h

+2 −0
Original line number Diff line number Diff line
@@ -69,6 +69,8 @@ struct jffs2_sb_info { 
	uint8_t resv_blocks_gctrigger;	/* ... wake up the GC thread */

	uint8_t resv_blocks_gcbad;	/* ... pick a block from the bad_list to GC */

	uint8_t resv_blocks_gcmerge;	/* ... merge pages when garbage collecting */

	/* Number of 'very dirty' blocks before we trigger immediate GC */

	uint8_t vdirty_blocks_gctrigger;



	uint32_t nospc_dirty_size;

fs/jffs2/nodemgmt.c

+12 −2
Original line number Diff line number Diff line
@@ -722,6 +722,8 @@ int jffs2_thread_should_wake(struct jffs2_sb_info *c) 
{

	int ret = 0;

	uint32_t dirty;

	int nr_very_dirty = 0;

	struct jffs2_eraseblock *jeb;



	if (c->unchecked_size) {

		D1(printk(KERN_DEBUG "jffs2_thread_should_wake(): unchecked_size %d, checked_ino #%d\n",
@@ -743,8 +745,16 @@ int jffs2_thread_should_wake(struct jffs2_sb_info *c) 
			(dirty > c->nospc_dirty_size))

		ret = 1;



	D1(printk(KERN_DEBUG "jffs2_thread_should_wake(): nr_free_blocks %d, nr_erasing_blocks %d, dirty_size 0x%x: %s\n",

		  c->nr_free_blocks, c->nr_erasing_blocks, c->dirty_size, ret?"yes":"no"));

	list_for_each_entry(jeb, &c->very_dirty_list, list) {

		nr_very_dirty++;

		if (nr_very_dirty == c->vdirty_blocks_gctrigger) {

			ret = 1;

			D1(break);

		}

	}



	D1(printk(KERN_DEBUG "jffs2_thread_should_wake(): nr_free_blocks %d, nr_erasing_blocks %d, dirty_size 0x%x, vdirty_blocks %d: %s\n",

		  c->nr_free_blocks, c->nr_erasing_blocks, c->dirty_size, nr_very_dirty, ret?"yes":"no"));



	return ret;

}