On Sat, Sep 22, 2007 at 03:16:22PM +0200, Peter Zijlstra wrote: > On Sat, 22 Sep 2007 09:55:09 +0800 Fengguang Wu <[EMAIL PROTECTED]> > wrote: > > > --- linux-2.6.22.orig/mm/page-writeback.c > > +++ linux-2.6.22/mm/page-writeback.c > > @@ -426,6 +426,14 @@ static void balance_dirty_pages(struct a > > bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); > > } > > > > + printk(KERN_DEBUG "balance_dirty_pages written %lu %lu > > congested %d limits %lu %lu %lu %lu %lu %ld\n", > > + pages_written, > > + write_chunk - wbc.nr_to_write, > > + bdi_write_congested(bdi), > > + background_thresh, dirty_thresh, > > + bdi_thresh, bdi_nr_reclaimable, > > bdi_nr_writeback, > > + bdi_thresh - bdi_nr_reclaimable - > > bdi_nr_writeback); > > + > > if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) > > break; > > if (pages_written >= write_chunk) > > > > > [ 1305.361511] balance_dirty_pages written 0 0 congested 0 limits 48869 > > 195477 5801 5760 288 -247 > > <snip long series of mostly identical lines> > > Could you perhaps instrument the writeback_inodes() path to see why > nothing is written out? - the attached patch would be a nice start.
Curiously the lockup problem disappeared after upgrading to 2.6.23-rc6-mm1. (need to watch it in a longer time window). Anyway here's the output of your patch: sb_locked 0 sb_empty 97011 > Most peculiar. It seems writeback_inodes() doesn't even attempt to > write out stuff. Nor are outstanding writeback pages completed. Still true. Another problem is that balance_dirty_pages() is being called even when there are only 54 dirty pages. That could slow down writers unnecessarily. balance_dirty_pages() should not be entered at all with small nr_dirty. Look at these lines: [ 197.471619] balance_dirty_pages for tar written 405 405 congested 0 global 196554 54 403 196097 bdi 0 0 398 -398 [ 197.472196] balance_dirty_pages for tar written 405 0 congested 0 global 196554 54 372 196128 bdi 0 0 380 -380 [ 197.472893] balance_dirty_pages for tar written 405 0 congested 0 global 196554 54 372 196128 bdi 23 0 369 -346 [ 197.473158] balance_dirty_pages for tar written 405 0 congested 0 global 196554 54 372 196128 bdi 23 0 366 -343 [ 197.473403] balance_dirty_pages for tar written 405 0 congested 0 global 196554 54 372 196128 bdi 23 0 365 -342 [ 197.473674] balance_dirty_pages for tar written 405 0 congested 0 global 196554 54 372 196128 bdi 23 0 364 -341 [ 197.474265] balance_dirty_pages for tar written 405 0 congested 0 global 196554 54 372 196128 bdi 23 0 362 -339 [ 197.475440] balance_dirty_pages for tar written 405 0 congested 0 global 196554 54 341 196159 bdi 47 0 327 -280 [ 197.476970] balance_dirty_pages for tar written 405 0 congested 0 global 196546 54 279 196213 bdi 95 0 279 -184 [ 197.477773] balance_dirty_pages for tar written 405 0 congested 0 global 196546 54 248 196244 bdi 95 0 255 -160 [ 197.479463] balance_dirty_pages for tar written 405 0 congested 0 global 196546 54 217 196275 bdi 143 0 210 -67 [ 197.479656] balance_dirty_pages for tar written 405 0 congested 0 global 196546 54 217 196275 bdi 143 0 209 -66 [ 197.481159] balance_dirty_pages for tar written 405 0 congested 0 global 196546 54 155 196337 bdi 167 0 163 4 The trace messages are generated by the following code: --- linux-2.6.23-rc6-mm1.orig/mm/page-writeback.c +++ linux-2.6.23-rc6-mm1/mm/page-writeback.c @@ -421,6 +421,18 @@ static void balance_dirty_pages(struct a bdi_nr_writeback = bdi_stat(bdi, BDI_WRITEBACK); } + printk(KERN_DEBUG "balance_dirty_pages for %s written %lu %lu congested %d " + "global %lu %lu %lu %ld bdi %lu %lu %lu %ld\n", + current->comm, + pages_written, write_chunk - wbc.nr_to_write, + bdi_write_congested(bdi), + dirty_thresh, + global_dirty_unstable_pages(), global_page_state(NR_WRITEBACK), + dirty_thresh - + global_dirty_unstable_pages() - global_page_state(NR_WRITEBACK), + bdi_thresh, bdi_nr_reclaimable, bdi_nr_writeback, + bdi_thresh - bdi_nr_reclaimable - bdi_nr_writeback); + if (bdi_nr_reclaimable + bdi_nr_writeback <= bdi_thresh) break; if (pages_written >= write_chunk) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/