On Thu, Dec 08, 2011 at 12:07:53AM +0800, Jan Kara wrote: > On Wed 07-12-11 20:08:18, Wu Fengguang wrote: > > On Wed, Dec 07, 2011 at 06:53:40PM +0800, Jan Kara wrote: > > > On Mon 28-11-11 21:53:41, Wu Fengguang wrote: > > > > When dd in 512bytes, generic_perform_write() calls > > > > balance_dirty_pages_ratelimited() 8 times for the same page, but > > > > obviously the page is only dirtied once. > > > Actually, for ppc where pages can be 64 KB the problem is even worse. > > > > Ah yes. > > > > > > Fix it by accounting tsk->nr_dirtied and bdp_ratelimits at page dirty time. > > > I was wondering about one more thing - couldn't we rather check in > > > generic_perform_write() whether the page was dirty before calling > > > ->write_end and call balance_dirty_pages_ratelimited() only if it wasn't? > > > > Cough.. the very original version does that exactly, then you raised > > some concern here: > > > > https://lkml.org/lkml/2011/4/13/554 > > > > The discussion goes on and eventually I get to the current version > > that looks most acceptable in the three options. > Good point. I should have researched web (or my memory) more closely ;) > Thanks for the pointer - it has reminded me why using PageDirty isn't quite > perfect. > > > > For generic_perform_write() it doesn't really matter that much since we > > > do things page-by-page anyway but other callers could be more efficient... > > > > That's right. > You can add: > Acked-by: Jan Kara <jack@xxxxxxx> OK, thanks! Fengguang -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
