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Subject[PATCH 2/3] f2fs: add sysfs entries to select the gc policy
Date
From: Namjae Jeon <namjae.jeon@samsung.com>

Add sysfs entry gc_idle to control the gc policy. Where
gc_idle = 1 corresponds to selecting a cost benefit approach,
while gc_idle = 2 corresponds to selecting a greedy approach
to garbage collection. The selection is mutually exclusive one
approach will work at any point. If gc_idle = 0, then this
option is disabled.

Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Pankaj Kumar <pankaj.km@samsung.com>
---
Documentation/ABI/testing/sysfs-fs-f2fs | 6 +++++-
Documentation/filesystems/f2fs.txt | 6 ++++++
fs/f2fs/gc.c | 24 +++++++++++++++++++++---
fs/f2fs/gc.h | 3 +++
fs/f2fs/super.c | 2 ++
5 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 5f44095..31942ef 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -19,4 +19,8 @@ Description:
Controls the default sleep time for gc_thread. Time
is in milliseconds.

-
+What: /sys/fs/f2fs/<disk>/gc_idle
+Date: July 2013
+Contact: "Namjae Jeon" <namjae.jeon@samsung.com>
+Description:
+ Controls the victim selection policy for garbage collection.
diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index 5daf3bb..3cd27be 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -158,6 +158,12 @@ Files in /sys/fs/f2fs/<devname>
time for the garbage collection thread. Time is
in milliseconds.

+ gc_idle This parameter controls the selection of victim
+ policy for garbage collection. Setting gc_idle = 0
+ (default) will disable this option. Setting
+ gc_idle = 1 will select the Cost Benefit approach
+ & setting gc_idle = 2 will select the greedy aproach.
+
================================================================================
USAGE
================================================================================
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 60d4f67..2c0c8ad 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -106,6 +106,8 @@ int start_gc_thread(struct f2fs_sb_info *sbi)
gc_th->max_sleep_time = DEF_GC_THREAD_MAX_SLEEP_TIME;
gc_th->no_gc_sleep_time = DEF_GC_THREAD_NOGC_SLEEP_TIME;

+ gc_th->gc_idle = 0;
+
sbi->gc_thread = gc_th;
init_waitqueue_head(&sbi->gc_thread->gc_wait_queue_head);
sbi->gc_thread->f2fs_gc_task = kthread_run(gc_thread_func, sbi,
@@ -130,9 +132,25 @@ void stop_gc_thread(struct f2fs_sb_info *sbi)
sbi->gc_thread = NULL;
}

-static int select_gc_type(int gc_type)
+static int select_gc_type(struct f2fs_gc_kthread *gc_th, int gc_type)
{
- return (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
+ int gc_mode;
+
+ if (gc_th && gc_th->gc_idle) {
+ /* Cost Benefit Policy */
+ if (gc_th->gc_idle == 1) {
+ gc_mode = GC_CB;
+ goto out;
+ } else if (gc_th->gc_idle == 2) {
+ /* Greedy Policy */
+ gc_mode = GC_GREEDY;
+ goto out;
+ }
+ }
+
+ gc_mode = (gc_type == BG_GC) ? GC_CB : GC_GREEDY;
+out:
+ return gc_mode;
}

static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
@@ -145,7 +163,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
p->dirty_segmap = dirty_i->dirty_segmap[type];
p->ofs_unit = 1;
} else {
- p->gc_mode = select_gc_type(gc_type);
+ p->gc_mode = select_gc_type(sbi->gc_thread, gc_type);
p->dirty_segmap = dirty_i->dirty_segmap[DIRTY];
p->ofs_unit = sbi->segs_per_sec;
}
diff --git a/fs/f2fs/gc.h b/fs/f2fs/gc.h
index f4bf44c..c22dee9 100644
--- a/fs/f2fs/gc.h
+++ b/fs/f2fs/gc.h
@@ -30,6 +30,9 @@ struct f2fs_gc_kthread {
unsigned int min_sleep_time;
unsigned int max_sleep_time;
unsigned int no_gc_sleep_time;
+
+ /* for changing gc mode */
+ unsigned int gc_idle;
};

struct inode_entry {
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 0a3e88f..f9c6c0b 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -148,12 +148,14 @@ static struct f2fs_attr f2fs_attr_##_name = { \
F2FS_RW_ATTR(gc_min_sleep_time, min_sleep_time);
F2FS_RW_ATTR(gc_max_sleep_time, max_sleep_time);
F2FS_RW_ATTR(gc_no_gc_sleep_time, no_gc_sleep_time);
+F2FS_RW_ATTR(gc_idle, gc_idle);

#define ATTR_LIST(name) (&f2fs_attr_##name.attr)
static struct attribute *f2fs_attrs[] = {
ATTR_LIST(gc_min_sleep_time),
ATTR_LIST(gc_max_sleep_time),
ATTR_LIST(gc_no_gc_sleep_time),
+ ATTR_LIST(gc_idle),
NULL,
};

--
1.7.9.5


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