On Mon 09-11-15 14:21:11, Namjae Jeon wrote:
> >
> > 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.
Hum, why such pages didn't get freed by release_buffer_page() call
happening when processing transaction's forget list? Because the idea is
that such pages should be discarded at that point...
Honza
>
> ---
> 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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--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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