Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [RFC 1/2] deactive invalidated pages | Date | Tue, 23 Nov 2010 17:01:14 +0900 (JST) |
| |
> Hi KOSAKI, > > 2010/11/23 KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>: > >> By Other approach, app developer uses POSIX_FADV_DONTNEED. > >> But it has a problem. If kernel meets page is writing > >> during invalidate_mapping_pages, it can't work. > >> It is very hard for application programmer to use it. > >> Because they always have to sync data before calling > >> fadivse(..POSIX_FADV_DONTNEED) to make sure the pages could > >> be discardable. At last, they can't use deferred write of kernel > >> so that they could see performance loss. > >> (http://insights.oetiker.ch/linux/fadvise.html) > > > > If rsync use the above url patch, we don't need your patch. > > fdatasync() + POSIX_FADV_DONTNEED should work fine. > > It works well. But it needs always fdatasync before calling fadvise. > For small file, it hurt performance since we can't use the deferred write.
I doubt rsync need to call fdatasync. Why?
If rsync continue to do following loop, some POSIX_FADV_DONTNEED may not drop some dirty pages. But they can be dropped at next loop's POSIX_FADV_DONTNEED. Then, It doesn't make serious issue.
1) read 2) write 3) POSIX_FADV_DONTNEED 4) goto 1
Am I missing anything?
> > So, I think the core worth of previous PeterZ's patch is in readahead > > based heuristics. I'm curious why you drop it. > > > > In previous peter's patch, it couldn't move active page into inactive list. > So it's not what i want and I think invalidation is stronger hint than > the readahead heuristic. > But if we need it, I will add it in my series. It can help reclaiming > unnecessary inactive page asap. > but before that, I hope we make sure fadvise works well enough.
I've got it.Yeah, 1) implement manual oepration 2) add automatic heuristic is right order. I think. we can easily test your one.
> >> In fact, invalidate is very big hint to reclaimer. > >> It means we don't use the page any more. So let's move > >> the writing page into inactive list's head. > > > > But, I agree this. > > Thank you. > > >> +static void __pagevec_lru_deactive(struct pagevec *pvec) > >> +{ > >> + int i, lru, file; > >> + > >> + struct zone *zone = NULL; > >> + > >> + for (i = 0; i < pagevec_count(pvec); i++) { > >> + struct page *page = pvec->pages[i]; > >> + struct zone *pagezone = page_zone(page); > >> + > >> + if (pagezone != zone) { > >> + if (zone) > >> + spin_unlock_irq(&zone->lru_lock); > >> + zone = pagezone; > >> + spin_lock_irq(&zone->lru_lock); > >> + } > >> + > >> + if (PageLRU(page)) { > >> + if (PageActive(page)) { > >> + file = page_is_file_cache(page); > >> + lru = page_lru_base_type(page); > >> + del_page_from_lru_list(zone, page, > >> + lru + LRU_ACTIVE); > >> + ClearPageActive(page); > >> + ClearPageReferenced(page); > >> + add_page_to_lru_list(zone, page, lru); > >> + __count_vm_event(PGDEACTIVATE); > >> + > >> + update_page_reclaim_stat(zone, page, file, 0); > > > > When PageActive is unset, we need to change cgroup lru too. > > Doesn't add_page_to_lru_list/del_page_from_lru_list do it?
Grr, my fault. I've forgot to we changed add_page_to_lru_list.
-- 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/
| |