Change page reference handling semantic of page cache

PATCH Superseded Minchan Kim 4 participants 17 messages Dec 22, 2010 – Jan 10, 2011

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Memory management MGLRU Page cache MM reclaim +3 more subsystems

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Minchan Kim

author

2010-12-22 15:33 UTC #0 lore raw

cover Change page reference handling semantic of page cache

Now we increases page reference on add_to_page_cache but doesn't decrease it in remove_from_page_cache. Such asymmetric makes confusing about page reference so that caller should notice it and comment why they release page reference. It's not good API.

Long time ago, Hugh tried it[1] but gave up of reason which reiser4's drop_page had to unlock the page between removing it from page cache and doing the page_cache_release. But now the situation is changed. I think at least things in current mainline doesn't have any obstacles. The problem is fs or somethings out of mainline. If it has done such thing like reiser4, this patch could be a problem but they found it when compile time since we remove remove_from_page_cache.

[1] http://lkml.org/lkml/2004/10/24/140

The series configuration is following as.

[1/7] : This patch introduces new API delete_from_page_cache. [2,3,4,5/7] : Change remove_from_page_cache with delete_from_page_cache. Intentionally I divide patch per file since someone might have a concern about releasing page reference of delete_from_page_cache in somecase (ex, truncate.c)
[6/7] : Remove old API so out of fs can meet compile error when build time and can notice it.
[7/7] : Change __remove_from_page_cache with __delete_from_page_cache, too. In this time, I made all-in-one patch because it doesn't change old behavior so it has no concern. Just clean up patch.

Minchan Kim (7):
[1/7] Introduce delete_from_page_cache
[2/7] fuse: Change remove_from_page_cache
[3/7] tlbfs: Change remove_from_page_cache
[4/7] swap: Change remove_from_page_cache
[5/7] truncate: Change remove_from_page_cache
[6/7] Good bye remove_from_page_cache
[7/7] Change __remove_from_page_cache

 fs/fuse/dev.c           |    3 +--
 fs/hugetlbfs/inode.c    |    3 +--
 include/linux/pagemap.h |    4 ++--
 mm/filemap.c            |   22 +++++++++++++++++-----
 mm/shmem.c              |    3 +--
 mm/truncate.c           |    5 ++---
 mm/vmscan.c             |    2 +-
 7 files changed, 25 insertions(+), 17 deletions(-)

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Minchan Kim

author

2010-12-22 15:33 UTC #1 lore raw

PATCH 1/7 Introduce delete_from_page_cache

This function works as just wrapper remove_from_page_cache. The difference is that it decreases page references in itself. So caller have to make sure it has a page reference before calling.

This patch is ready for removing remove_from_page_cache.

Cc Christoph Hellwig <[email protected]>

Cc Hugh Dickins <[email protected]>

Signed-off-by Minchan Kim <[email protected]>

---
 include/linux/pagemap.h |    1 +
 mm/filemap.c            |   17 +++++++++++++++++
 2 files changed, 18 insertions(+), 0 deletions(-)

include/linux/pagemap.h +1 -0

index 9c66e99..7a1cb49 100644
@@ -457,6 +457,7 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 				pgoff_t index, gfp_t gfp_mask);
 extern void remove_from_page_cache(struct page *page);
 extern void __remove_from_page_cache(struct page *page);
+extern void delete_from_page_cache(struct page *page);
 
 /*
  * Like add_to_page_cache_locked, but used to add newly allocated pages:

mm/filemap.c +17 -0

index 095c393..1ca7475 100644
@@ -166,6 +166,23 @@ void remove_from_page_cache(struct page *page)
 }
 EXPORT_SYMBOL(remove_from_page_cache);
 
+/**
+ * delete_from_page_cache - delete page from page cache
+ *
+ * @page: the page which the kernel is trying to remove from page cache
+ *
+ * This must be called only on pages that have
+ * been verified to be in the page cache and locked.
+ * It will never put the page into the free list,
+ * the caller has a reference on the page.
+ */
+void delete_from_page_cache(struct page *page)
+{
+	remove_from_page_cache(page);
+	page_cache_release(page);
+}
+EXPORT_SYMBOL(delete_from_page_cache);
+
 static int sync_page(void *word)
 {
 	struct address_space *mapping;

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Minchan Kim

author

2010-12-22 15:33 UTC #2 lore raw

PATCH 2/7 fuse: Change remove_from_page_cache

In reply to Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.

Cc Miklos Szeredi <[email protected]>

Cc [email protected]

Signed-off-by Minchan Kim <[email protected]>

Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

---
 fs/fuse/dev.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

fs/fuse/dev.c +1 -2

index cf8d28d..1ef24fb 100644
@@ -737,8 +737,7 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 	if (WARN_ON(PageMlocked(oldpage)))
 		goto out_fallback_unlock;
 
-	remove_from_page_cache(oldpage);
-	page_cache_release(oldpage);
+	delete_from_page_cache(oldpage);
 
 	err = add_to_page_cache_locked(newpage, mapping, index, GFP_KERNEL);
 	if (err) {

Signature · 1 line

1.7.0.4

Johannes Weiner

maintainer Reviewed-by on v1 2/7

2011-01-08 22:22 UTC #3 lore raw

Re: [PATCH 2/7] fuse: Change remove_from_page_cache

Quoted 8 lines · Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.
Cc Miklos Szeredi <[email protected]>
Cc [email protected]
Signed-off-by Minchan Kim <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

Reviewed-by Johannes Weiner <[email protected]>

Minchan Kim

author

2010-12-22 15:33 UTC #4 lore raw

PATCH 3/7 tlbfs: Change remove_from_page_cache

In reply to Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.

Cc William Irwin <[email protected]>

Signed-off-by Minchan Kim <[email protected]>

Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

---
 fs/hugetlbfs/inode.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

fs/hugetlbfs/inode.c +1 -2

index 9885082..b9eeb1c 100644
@@ -332,8 +332,7 @@ static void truncate_huge_page(struct page *page)
 {
 	cancel_dirty_page(page, /* No IO accounting for huge pages? */0);
 	ClearPageUptodate(page);
-	remove_from_page_cache(page);
-	put_page(page);
+	delete_from_page_cache(page);
 }
 
 static void truncate_hugepages(struct inode *inode, loff_t lstart)

Signature · 1 line

1.7.0.4

Johannes Weiner

maintainer Reviewed-by on v1 3/7

2011-01-08 22:25 UTC #5 lore raw

Re: [PATCH 3/7] tlbfs: Change remove_from_page_cache

Quoted 7 lines · Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.
Cc William Irwin <[email protected]>
Signed-off-by Minchan Kim <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

As Mel pointed out, that should be hugetlbfs in the subject. Otherwise, the patch looks good.

Reviewed-by Johannes Weiner <[email protected]>

Minchan Kim

author

2010-12-22 15:34 UTC #6 lore raw

PATCH 4/7 swap: Change remove_from_page_cache

In reply to Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.

Cc Hugh Dickins <[email protected]>

Signed-off-by Minchan Kim <[email protected]>

Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

---
 mm/shmem.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

mm/shmem.c +1 -2

index fa9acc9..079cced 100644
@@ -1081,7 +1081,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	shmem_recalc_inode(inode);
 
 	if (swap.val && add_to_swap_cache(page, swap, GFP_ATOMIC) == 0) {
-		remove_from_page_cache(page);
+		delete_from_page_cache(page);
 		shmem_swp_set(info, entry, swap.val);
 		shmem_swp_unmap(entry);
 		if (list_empty(&info->swaplist))

@@ -1091,7 +1091,6 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 		spin_unlock(&info->lock);
 		swap_shmem_alloc(swap);
 		BUG_ON(page_mapped(page));
-		page_cache_release(page);	/* pagecache ref */
 		swap_writepage(page, wbc);
 		if (inode) {
 			mutex_lock(&shmem_swaplist_mutex);

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1.7.0.4

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Johannes Weiner

maintainer Reviewed-by on v1 4/7

2011-01-08 22:28 UTC #7 lore raw

Re: [PATCH 4/7] swap: Change remove_from_page_cache

Quoted 9 lines · Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.
Cc Hugh Dickins <[email protected]>
Signed-off-by Minchan Kim <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>
---
 mm/shmem.c |    3 +--

Patch subject should probably say 'shmem' instead of 'swap'.

Otherwise,

Reviewed-by Johannes Weiner <[email protected]>

Minchan Kim

author

2011-01-10 15:45 UTC #8 lore raw

Re: [PATCH 4/7] swap: Change remove_from_page_cache

Quoted 5 lines · Johannes Weiner

Quoted 4 lines · Minchan Kim
This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.

Quoted 7 lines

Quoted 5 lines
Cc Hugh Dickins <[email protected]>
Signed-off-by Minchan Kim <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>
---
mm/shmem.c | 3 +--
Patch subject should probably say 'shmem' instead of 'swap'.

Thanks, Hannes.
Will fix.

Quoted 4 lines

Otherwise,
Reviewed-by Johannes Weiner <[email protected]>

Signature · 2 lines

Kind regards,
Minchan Kim

Minchan Kim

author

2010-12-22 15:34 UTC #9 lore raw

PATCH 5/7 truncate: Change remove_from_page_cache

In reply to Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.

Cc Dan Magenheimer <[email protected]>

Cc Andi Kleen <[email protected]>

Cc Nick Piggin <[email protected]>

Cc Al Viro <[email protected]>

Cc [email protected]

Signed-off-by Minchan Kim <[email protected]>

Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

---
 mm/truncate.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

mm/truncate.c +1 -2

index 9ee5673..3adb9c0 100644
@@ -108,13 +108,12 @@ truncate_complete_page(struct address_space *mapping, struct page *page)
 	cancel_dirty_page(page, PAGE_CACHE_SIZE);
 
 	clear_page_mlock(page);
-	remove_from_page_cache(page);
+	delete_from_page_cache(page);
 	ClearPageMappedToDisk(page);
 	/* this must be after the remove_from_page_cache which
 	 * calls cleancache_put_page (and note page->mapping is now NULL)
 	 */
 	cleancache_flush_page(mapping, page);
-	page_cache_release(page);	/* pagecache ref */
 	return 0;
 }

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1.7.0.4

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Johannes Weiner

maintainer Reviewed-by on v1 5/7

2011-01-08 22:33 UTC #10 lore raw

Re: [PATCH 5/7] truncate: Change remove_from_page_cache

Quoted 11 lines · Minchan Kim

This patch series changes remove_from_page_cache's page ref counting rule. Page cache ref count is decreased in delete_from_page_cache. So we don't need decreasing page reference by caller.
Cc Dan Magenheimer <[email protected]>
Cc Andi Kleen <[email protected]>
Cc Nick Piggin <[email protected]>
Cc Al Viro <[email protected]>
Cc [email protected]
Signed-off-by Minchan Kim <[email protected]>
Reviewed-by KAMEZAWA Hiroyuki <[email protected]>

Reviewed-by Johannes Weiner <[email protected]>

Minchan Kim

author

2010-12-22 15:34 UTC #11 lore raw

PATCH 6/7 Good bye remove_from_page_cache

In reply to Minchan Kim

Now delete_from_page_cache replaces remove_from_page_cache. So we remove remove_from_page_cache so fs or something out of mainline will notice it when compile time and can fix it.

Cc Christoph Hellwig <[email protected]>

Cc Hugh Dickins <[email protected]>

Signed-off-by Minchan Kim <[email protected]>

---
 include/linux/pagemap.h |    1 -
 mm/filemap.c            |   27 +++++++++++----------------
 2 files changed, 11 insertions(+), 17 deletions(-)

include/linux/pagemap.h +0 -1

index 7a1cb49..7bf6587 100644
@@ -455,7 +455,6 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 				pgoff_t index, gfp_t gfp_mask);
 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 				pgoff_t index, gfp_t gfp_mask);
-extern void remove_from_page_cache(struct page *page);
 extern void __remove_from_page_cache(struct page *page);
 extern void delete_from_page_cache(struct page *page);

mm/filemap.c +11 ~~-16~~

index 1ca7475..a4c43f7 100644
@@ -148,7 +148,17 @@ void __remove_from_page_cache(struct page *page)
 	}
 }
 
-void remove_from_page_cache(struct page *page)
+/**
+ * delete_from_page_cache - delete page from page cache
+ *
+ * @page: the page which the kernel is trying to remove from page cache
+ *
+ * This must be called only on pages that have
+ * been verified to be in the page cache and locked.
+ * It will never put the page into the free list,
+ * the caller has a reference on the page.
+ */
+void delete_from_page_cache(struct page *page)
 {
 	struct address_space *mapping = page->mapping;
 	void (*freepage)(struct page *);

@@ -163,22 +173,7 @@ void remove_from_page_cache(struct page *page)
 
 	if (freepage)
 		freepage(page);
-}
-EXPORT_SYMBOL(remove_from_page_cache);
 
-/**
- * delete_from_page_cache - delete page from page cache
- *
- * @page: the page which the kernel is trying to remove from page cache
- *
- * This must be called only on pages that have
- * been verified to be in the page cache and locked.
- * It will never put the page into the free list,
- * the caller has a reference on the page.
- */
-void delete_from_page_cache(struct page *page)
-{
-	remove_from_page_cache(page);
 	page_cache_release(page);
 }
 EXPORT_SYMBOL(delete_from_page_cache);

Signature · 8 lines

1.7.0.4

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Johannes Weiner

maintainer Reviewed-by on v1 6/7

2011-01-08 22:35 UTC #12 lore raw

Re: [PATCH 6/7] Good bye remove_from_page_cache

Quoted 7 lines · Minchan Kim

Now delete_from_page_cache replaces remove_from_page_cache. So we remove remove_from_page_cache so fs or something out of mainline will notice it when compile time and can fix it.
Cc Christoph Hellwig <[email protected]>
Cc Hugh Dickins <[email protected]>
Signed-off-by Minchan Kim <[email protected]>

Reviewed-by Johannes Weiner <[email protected]>

Minchan Kim

author

2010-12-22 15:34 UTC #13 lore raw

PATCH 7/7 Change __remove_from_page_cache

In reply to Minchan Kim

Now we renamed remove_from_page_cache with delete_from_page_cache. As consistency of __remove_from_swap_cache and remove_from_swap_cache, We change internal page cache handling function name, too.

Cc Christoph Hellwig <[email protected]>

Cc Hugh Dickins <[email protected]>

Signed-off-by Minchan Kim <[email protected]>

---
 include/linux/pagemap.h |    2 +-
 mm/filemap.c            |    6 +++---
 mm/truncate.c           |    2 +-
 mm/vmscan.c             |    2 +-
 4 files changed, 6 insertions(+), 6 deletions(-)

include/linux/pagemap.h +1 -1

index 7bf6587..b5b21d8 100644
@@ -455,7 +455,7 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
 				pgoff_t index, gfp_t gfp_mask);
 int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
 				pgoff_t index, gfp_t gfp_mask);
-extern void __remove_from_page_cache(struct page *page);
+extern void __delete_from_page_cache(struct page *page);
 extern void delete_from_page_cache(struct page *page);
 
 /*

mm/filemap.c +3 -3

index a4c43f7..9776166 100644
@@ -109,11 +109,11 @@
  */
 
 /*
- * Remove a page from the page cache and free it. Caller has to make
+ * Delete a page from the page cache and free it. Caller has to make
  * sure the page is locked and that nobody else uses it - or that usage
  * is safe.  The caller must hold the mapping's tree_lock.
  */
-void __remove_from_page_cache(struct page *page)
+void __delete_from_page_cache(struct page *page)
 {
 	struct address_space *mapping = page->mapping;

@@ -167,7 +167,7 @@ void delete_from_page_cache(struct page *page)
 
 	freepage = mapping->a_ops->freepage;
 	spin_lock_irq(&mapping->tree_lock);
-	__remove_from_page_cache(page);
+	__delete_from_page_cache(page);
 	spin_unlock_irq(&mapping->tree_lock);
 	mem_cgroup_uncharge_cache_page(page);

mm/truncate.c +1 -1

index 3adb9c0..687429a 100644
@@ -402,7 +402,7 @@ invalidate_complete_page2(struct address_space *mapping, struct page *page)
 
 	clear_page_mlock(page);
 	BUG_ON(page_has_private(page));
-	__remove_from_page_cache(page);
+	__delete_from_page_cache(page);
 	spin_unlock_irq(&mapping->tree_lock);
 	mem_cgroup_uncharge_cache_page(page);

mm/vmscan.c +1 -1

index 47a5096..bdb867f 100644
@@ -515,7 +515,7 @@ static int __remove_mapping(struct address_space *mapping, struct page *page)
 
 		freepage = mapping->a_ops->freepage;
 
-		__remove_from_page_cache(page);
+		__delete_from_page_cache(page);
 		spin_unlock_irq(&mapping->tree_lock);
 		mem_cgroup_uncharge_cache_page(page);

Signature · 8 lines

1.7.0.4

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Johannes Weiner

maintainer Reviewed-by on v1 7/7

2011-01-08 22:36 UTC #14 lore raw

Re: [PATCH 7/7] Change __remove_from_page_cache

Quoted 7 lines · Minchan Kim

Now we renamed remove_from_page_cache with delete_from_page_cache. As consistency of __remove_from_swap_cache and remove_from_swap_cache, We change internal page cache handling function name, too.
Cc Christoph Hellwig <[email protected]>
Cc Hugh Dickins <[email protected]>
Signed-off-by Minchan Kim <[email protected]>

Reviewed-by Johannes Weiner <[email protected]>

Hugh Dickins

maintainer Acked-by on the v1 series

2010-12-30 03:17 UTC #15 lore raw

In reply to Minchan Kim

Quoted 37 lines · Minchan Kim

Now we increases page reference on add_to_page_cache but doesn't decrease it in remove_from_page_cache. Such asymmetric makes confusing about page reference so that caller should notice it and comment why they release page reference. It's not good API.
Long time ago, Hugh tried it[1] but gave up of reason which reiser4's drop_page had to unlock the page between removing it from page cache and doing the page_cache_release. But now the situation is changed. I think at least things in current mainline doesn't have any obstacles. The problem is fs or somethings out of mainline. If it has done such thing like reiser4, this patch could be a problem but they found it when compile time since we remove remove_from_page_cache.
[1] http://lkml.org/lkml/2004/10/24/140
The series configuration is following as.
[1/7] : This patch introduces new API delete_from_page_cache. [2,3,4,5/7] : Change remove_from_page_cache with delete_from_page_cache. Intentionally I divide patch per file since someone might have a concern about releasing page reference of delete_from_page_cache in somecase (ex, truncate.c)
[6/7] : Remove old API so out of fs can meet compile error when build time and can notice it.
[7/7] : Change __remove_from_page_cache with __delete_from_page_cache, too. In this time, I made all-in-one patch because it doesn't change old behavior so it has no concern. Just clean up patch.
Minchan Kim (7):
[1/7] Introduce delete_from_page_cache
[2/7] fuse: Change remove_from_page_cache
[3/7] tlbfs: Change remove_from_page_cache
[4/7] swap: Change remove_from_page_cache
[5/7] truncate: Change remove_from_page_cache
[6/7] Good bye remove_from_page_cache
[7/7] Change __remove_from_page_cache

Quoted 8 lines

 fs/fuse/dev.c           |    3 +--
 fs/hugetlbfs/inode.c    |    3 +--
 include/linux/pagemap.h |    4 ++--
 mm/filemap.c            |   22 +++++++++++++++++-----
 mm/shmem.c              |    3 +--
 mm/truncate.c           |    5 ++---
 mm/vmscan.c             |    2 +-
 7 files changed, 25 insertions(+), 17 deletions(-)

Acked-by Hugh Dickins <[email protected]>

for all seven: thanks.

Mel Gorman

Acked-by on the v1 series

2011-01-06 10:31 UTC #16 lore raw

In reply to Minchan Kim

Quoted 17 lines · Minchan Kim

Now we increases page reference on add_to_page_cache but doesn't decrease it in remove_from_page_cache. Such asymmetric makes confusing about page reference so that caller should notice it and comment why they release page reference. It's not good API.
Long time ago, Hugh tried it[1] but gave up of reason which reiser4's drop_page had to unlock the page between removing it from page cache and doing the page_cache_release. But now the situation is changed. I think at least things in current mainline doesn't have any obstacles. The problem is fs or somethings out of mainline. If it has done such thing like reiser4, this patch could be a problem but they found it when compile time since we remove remove_from_page_cache.
[1] http://lkml.org/lkml/2004/10/24/140
The series configuration is following as.

Quoted 11 lines

[1/7] : This patch introduces new API delete_from_page_cache. [2,3,4,5/7] : Change remove_from_page_cache with delete_from_page_cache. Intentionally I divide patch per file since someone might have a concern about releasing page reference of delete_from_page_cache in somecase (ex, truncate.c)
[6/7] : Remove old API so out of fs can meet compile error when build time and can notice it.
[7/7] : Change __remove_from_page_cache with __delete_from_page_cache, too. In this time, I made all-in-one patch because it doesn't change old behavior so it has no concern. Just clean up patch.

Other than hugetlbfs being called tlbfs in patch 3/7;

Acked-by Mel Gorman <[email protected]>

Signature · 3 lines

Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab