On Thu, 2010-07-08 at 14:20 +0200, Jens Axboe wrote: > On 2010-07-08 00:52, Christoph Hellwig wrote: > > Currently the per-bdi writeback thread is only created when there is > > dirty any dirty data on the BDI, and it lazy exists when it's been > > unused for some time. > > > > This leads to some very complex code, and the need to keep a forker > > thread around. > > > > This patch removes all this code and simply creates the thread as part > > of the bdi registration. The downside is that we use up ressoures > > for possible unused devices, although that overhead is rather low, > > with 8k kernel stack size on x86 and few other, even smaller ressources. > > > > If the overhead is still considered too much I can look into starting > > the thread explicitly instead of as part of the bdi registration, but > > that will require a bit of code complexity, too. > > I'm pretty sure this will come back to bite us in the ass... If we are > going to change the lazy create/exit setup, I would greatly prefer > doing it at fs mount time (or something to that effect). How about not starting any thread at all at the bdi registration time, and start a bdi thread only when something for this bdi becomes dirty (__mark_inode_dirty()) or a bdi work is queued (bdi_queue_work())? If we do this, then the tasks can also die by the 5min timeout, and will be forked again when dirt/bdi works arrives? I guess it is a bit challenging to start a task in __mark_inode_dirty(), whis is supposed to be fast and non-sleeping, but we can just submit a work which will start the task. -- Best Regards, Artem Bityutskiy (Артём Битюцкий) -- 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
