Messages in this thread | | | Date | Fri, 10 Feb 2006 13:28:51 -0800 | From | Andrew Morton <> | Subject | Re: msync() behaviour broken for MS_ASYNC, revert patch? |
| |
Linus Torvalds <torvalds@osdl.org> wrote: > > > > On Fri, 10 Feb 2006, Andrew Morton wrote: > > > > Yes, it would make sense to run balance_dirty_pages_ratelimited() inside > > msync_pte_range(). So pdflush will get poked if we hit > > background_dirty_ratio threshold, or we go into caller-initiated writeout > > if we hit dirty_ratio. > > > > But it's not completely trivial, because I don't think we want to be doing > > blocking writeback with mmap_sem held. > > Why not just do it once, at the end? >
We could, sort-of.
balance_dirty_pages() is quite CPU-intensive (hence the presence of balance_dirty_pages_ratelimited()).
balance_dirty_pages_ratelimited() expects to be called once per page-dirtying.
- We can't use balance_dirty_pages() because workloads which do lots of teeny msyncs would chew lots of CPU.
- We can't use balance_dirty_pages_ratelimited() because it thinks only a single page was dirtied.
So the thing to do is to change msync to keep track of how many pages were dirtied, then at the end call
balance_dirty_pages_ratelimited_new_improved_api(mapping, nr_pages_dirtied).
Except an msync can cover multiple mappings, so we'd need to pop the lock in the top-level loop, run the above for each VMA. Not rocket-science, I guess. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |