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Subject[patch 32/35] fs: icache minimise I_FREEING latency
Problem with inode reclaim is that it puts inodes into I_FREEING state
and then continues to gather more, during which it may iput,
invalidate_mapping_pages, be preempted, etc. Holding these inodes in
I_FREEING can cause pauses.

After the inode scalability work, there is not a big reason to batch
up inodes to reclaim them, so dispose them as they are found from the
LRU.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

---
fs/inode.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)
Index: linux-2.6/fs/inode.c
===================================================================
--- linux-2.6.orig/fs/inode.c 2010-10-19 14:19:00.000000000 +1100
+++ linux-2.6/fs/inode.c 2010-10-19 14:19:18.000000000 +1100
@@ -410,6 +410,19 @@

static void inode_sb_list_del(struct inode *inode);

+static void dispose_one_inode(struct inode *inode)
+{
+ evict(inode);
+
+ spin_lock(&inode->i_lock);
+ __remove_inode_hash(inode);
+ inode_sb_list_del(inode);
+ spin_unlock(&inode->i_lock);
+
+ wake_up_inode(inode);
+ destroy_inode(inode);
+}
+
/*
* dispose_list - dispose of the contents of a local list
* @head: the head of the list to free
@@ -425,15 +438,8 @@
inode = list_first_entry(head, struct inode, i_lru);
list_del_init(&inode->i_lru);

- evict(inode);
-
- spin_lock(&inode->i_lock);
- __remove_inode_hash(inode);
- inode_sb_list_del(inode);
- spin_unlock(&inode->i_lock);
-
- wake_up_inode(inode);
- destroy_inode(inode);
+ dispose_one_inode(inode);
+ cond_resched();
}
}

@@ -557,7 +563,6 @@
*/
static void prune_icache(struct zone *zone, unsigned long nr_to_scan)
{
- LIST_HEAD(freeable);
unsigned long reap = 0;

down_read(&iprune_sem);
@@ -617,11 +622,15 @@
continue;
}
freeable:
- list_move(&inode->i_lru, &freeable);
+ list_del_init(&inode->i_lru);
WARN_ON(inode->i_state & I_NEW);
inode->i_state |= I_FREEING;
spin_unlock(&inode->i_lock);
zone->inode_nr_lru--;
+ spin_unlock(&zone->inode_lru_lock);
+ dispose_one_inode(inode);
+ cond_resched();
+ spin_lock(&zone->inode_lru_lock);
}
if (current_is_kswapd())
__count_vm_events(KSWAPD_INODESTEAL, reap);
@@ -629,7 +638,6 @@
__count_vm_events(PGINODESTEAL, reap);
spin_unlock(&zone->inode_lru_lock);

- dispose_list(&freeable);
up_read(&iprune_sem);
}




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