On Tue, Mar 24, 2009 at 05:43:10PM -0500, Don Porter wrote: > Thanks for the tip, Eric. > > I spent some time tracing through this in a debugger. > > I believe the lingering buffer_heads are allocated by > journal_write_commit_record()->journal_get_descriptor_buffer()->__getblk(). > The reference count ends up at zero, but the buffer head is never freed. > > As best I can tell, this is correct as long as the associated page is > cached, so that the associated buffer_head can be looked up and reused > later. > > I plan to look into this more, but perhaps the issue is just that the > kernel should be more aggressive about freeing cached journal pages? > They are highly unlikely to be used again once a committed transaction > is completely out on disk, as the journal is roughly an append-only log, > right? The journal is a fixed sized, circular log, so the buffer_head will be reused eventually. In the case of memory pressure the unreferenced buffer_head will be freed, but since we never reference the contents of the journal, we could be more aggressive about freeing the buffer_head just to avoid pushing out more valuable memory contents when we start getting put under memory pressure. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
