* [email protected] <[email protected]> [2010-03-09 10:29:28]:
> On Tue, 9 Mar 2010 09:19:14 +0900, KAMEZAWA Hiroyuki > <[email protected]> wrote: > > On Tue, 9 Mar 2010 01:12:52 +0100 > > Andrea Righi <[email protected]> wrote: > > > > > On Mon, Mar 08, 2010 at 05:31:00PM +0900, KAMEZAWA Hiroyuki wrote: > > > > On Mon, 8 Mar 2010 17:07:11 +0900 > > > > Daisuke Nishimura <[email protected]> wrote: > > > > > > > > > On Mon, 8 Mar 2010 11:37:11 +0900, KAMEZAWA Hiroyuki > > > > > <[email protected]> wrote: > > > > > > On Mon, 8 Mar 2010 11:17:24 +0900 > > > > > > Daisuke Nishimura <[email protected]> wrote: > > > > > > > > > > > > > > But IIRC, clear_writeback is done under treelock.... No ? > > > > > > > > > > > > > > > The place where NR_WRITEBACK is updated is out of tree_lock. > > > > > > > > > > > > > > 1311 int test_clear_page_writeback(struct page *page) > > > > > > > 1312 { > > > > > > > 1313 struct address_space *mapping = > > > > > > > page_mapping(page); > > > > > > > 1314 int ret; > > > > > > > 1315 > > > > > > > 1316 if (mapping) { > > > > > > > 1317 struct backing_dev_info *bdi = > > > > > > > mapping->backing_dev_info; > > > > > > > 1318 unsigned long flags; > > > > > > > 1319 > > > > > > > 1320 spin_lock_irqsave(&mapping->tree_lock, > > > > > > > flags); > > > > > > > 1321 ret = TestClearPageWriteback(page); > > > > > > > 1322 if (ret) { > > > > > > > 1323 > > > > > > > radix_tree_tag_clear(&mapping->page_tree, > > > > > > > 1324 > > > > > > > page_index(page), > > > > > > > 1325 > > > > > > > PAGECACHE_TAG_WRITEBACK); > > > > > > > 1326 if > > > > > > > (bdi_cap_account_writeback(bdi)) { > > > > > > > 1327 __dec_bdi_stat(bdi, > > > > > > > BDI_WRITEBACK); > > > > > > > 1328 __bdi_writeout_inc(bdi); > > > > > > > 1329 } > > > > > > > 1330 } > > > > > > > 1331 > > > > > > > spin_unlock_irqrestore(&mapping->tree_lock, flags); > > > > > > > 1332 } else { > > > > > > > 1333 ret = TestClearPageWriteback(page); > > > > > > > 1334 } > > > > > > > 1335 if (ret) > > > > > > > 1336 dec_zone_page_state(page, NR_WRITEBACK); > > > > > > > 1337 return ret; > > > > > > > 1338 } > > > > > > > > > > > > We can move this up to under tree_lock. Considering memcg, all our > > > > > > target has "mapping". > > > > > > > > > > > > If we newly account bounce-buffers (for NILFS, FUSE, etc..), which > > > > > > has no ->mapping, > > > > > > we need much more complex new charge/uncharge theory. > > > > > > > > > > > > But yes, adding new lock scheme seems complicated. (Sorry Andrea.) > > > > > > My concerns is performance. We may need somehing new > > > > > > re-implementation of > > > > > > locks/migrate/charge/uncharge. > > > > > > > > > > > I agree. Performance is my concern too. > > > > > > > > > > I made a patch below and measured the time(average of 10 times) of > > > > > kernel build > > > > > on tmpfs(make -j8 on 8 CPU machine with 2.6.33 defconfig). > > > > > > > > > > <before> > > > > > - root cgroup: 190.47 sec > > > > > - child cgroup: 192.81 sec > > > > > > > > > > <after> > > > > > - root cgroup: 191.06 sec > > > > > - child cgroup: 193.06 sec > > > > > > > > > > Hmm... about 0.3% slower for root, 0.1% slower for child. > > > > > > > > > > > > > Hmm...accepatable ? (sounds it's in error-range) > > > > > > > > BTW, why local_irq_disable() ? > > > > local_irq_save()/restore() isn't better ? > > > > > > Probably there's not the overhead of saving flags? > > maybe. > > > > > Anyway, it would make the code much more readable... > > > > > ok. > > > > please go ahead in this direction. Nishimura-san, would you post an > > independent patch ? If no, Andrea-san, please. > > > This is the updated version. > > Andrea-san, can you merge this into your patch set ? > Please please measure the performance overhead of this change. -- Three Cheers, Balbir _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
