>
> On Wed, Oct 21, 2015 at 06:44:10PM +0900, Namjae Jeon wrote:
> > > Interestingly we're not seeing these memory leaks on the truncate
> > > path, so I suspect the issue is in how collapse range is clearing
> > > pages from the page cache, especially pages that were freshly written
> > > to the journal by the commit but which hadn't yet been writtten to
> > > disk and then marked as complete so we can allow the relevant
> > > transaction to be checkpointed. (Although we're not leaking the
> > > journal head structures, but only the buffer heads, so the story most
> > > be a bit more complicated than that.)
> >
> > Okay, Thanks for sharing your view and points !!
> >
> > Currently I can reproduce memory leak issue without collase/insert/zero range.
> > conditions like the following.(collase/insert/zero range are disable with -I -C -z option and add -y
> option instead of -W)
> > 1. small size parition(1GB)
> > 2. run fsx with these options "./fsx -N 30000 -o 128000 -l 500000 -r 4096 -t 512 -w 512 -Z -R -y -
> I -C -z testfile"
> > And same result with generic/091 is showing (buffer_head leak)
> >
> > So I am starting to find root-cause base on your points.
> > I will share the result or the patch.
>
> Thanks, that's very interesting data point. So this makes it appear
> that the problem *is* probably with how we deal with checkpointing
> buffers after the pages get discarded using either a truncate or a
> collapse_range, since the 'y' option causes a lot fsync's, and hence
> commits, some of which are happening after a truncate command.
>
> Thanks for a taking a look at this. I really appreciate it.
>
> Cheers,
Hi Ted,
Could you review this patch?
Thanks!
---------------------------------------------------------------------------------
Subject: [PATCH] jbd2: try to free buffers from truncated page after
checkpoint
when ext4 is mounted in data=journal mode, and truncate operation
such as settatr(size), collopse, insert and zero range are used, there are
are many truncated pages with NULL page->mapping. Such truncated pages
pile up quickly due to truncate_pagecache on data pages associated with journal.
As page->mapping is NULL for such truncated pages, they are not freed
by drop cache(3) or umount. As a result, MemFree in /proc/meminfo decreases
quickly and active buffer_head slab objects grow in /proc/slabinfo.
This patch attempts to free buffers from such pages at the end of jbd2
checkpoint, if pages do not have any busy buffers and NULL mapping.
---
fs/jbd2/checkpoint.c | 11 +++++++++++
fs/jbd2/commit.c | 2 +-
include/linux/jbd2.h | 1 +
3 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index 4227dc4..bf68442 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -529,6 +529,7 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
transaction_t *transaction;
journal_t *journal;
int ret = 0;
+ struct buffer_head *bh;
JBUFFER_TRACE(jh, "entry");
@@ -538,10 +539,20 @@ int __jbd2_journal_remove_checkpoint(struct journal_head *jh)
}
journal = transaction->t_journal;
+ bh = jh2bh(jh);
+ get_bh(bh);
JBUFFER_TRACE(jh, "removing from transaction");
__buffer_unlink(jh);
jh->b_cp_transaction = NULL;
jbd2_journal_put_journal_head(jh);
+ /*
+ * if journal head is freed, try to free buffers from a truncated
+ * page, if page buffers are not busy and page->mapping is NULL
+ */
+ if (!buffer_jbd(bh))
+ release_buffer_page(bh);
+ else
+ __brelse(bh);
if (transaction->t_checkpoint_list != NULL ||
transaction->t_checkpoint_io_list != NULL)
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index b73e021..d94ec3f 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -63,7 +63,7 @@ static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
* Called under lock_journal(), and possibly under journal_datalist_lock. The
* caller provided us with a ref against the buffer, and we drop that here.
*/
-static void release_buffer_page(struct buffer_head *bh)
+void release_buffer_page(struct buffer_head *bh)
{
struct page *page;
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index edb640a..523f345 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1039,6 +1039,7 @@ int __jbd2_update_log_tail(journal_t *journal, tid_t tid, unsigned long block);
void jbd2_update_log_tail(journal_t *journal, tid_t tid, unsigned long block);
/* Commit management */
+extern void release_buffer_page(struct buffer_head *);
extern void jbd2_journal_commit_transaction(journal_t *);
/* Checkpoint list management */
----------------------------------------------------------
>
> - Ted
>
>
>
>
>
>
>
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