On Wed, Nov 18, 2009 at 06:38:49PM +0800, Peter Zijlstra wrote: > On Wed, 2009-11-18 at 16:27 +0800, Wu Fengguang wrote: > > plain text document attachment (bdi-debug-dump-sum.patch) > > CC: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > > Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> > > --- > > mm/backing-dev.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > --- linux.orig/mm/backing-dev.c 2009-11-18 16:25:28.000000000 +0800 > > +++ linux/mm/backing-dev.c 2009-11-18 16:26:10.000000000 +0800 > > @@ -104,8 +104,8 @@ static int bdi_debug_stats_show(struct s > > "wb_mask: %8lx\n" > > "wb_list: %8u\n" > > "wb_cnt: %8u\n", > > - (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)), > > - (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)), > > + (unsigned long) K(bdi_stat_sum(bdi, BDI_WRITEBACK)), > > + (unsigned long) K(bdi_stat_sum(bdi, BDI_RECLAIMABLE)), > > K(bdi_thresh), K(dirty_thresh), > > K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io, > > !list_empty(&bdi->bdi_list), bdi->state, bdi->wb_mask, > > > > Is this really important? This patch is basically a local DoS for large > machines. I did this patch after seeing inaccurate exported numbers, it may be confusing.. > Imagine someone doing: > > while :; do cat /debug/bdi/*/stats; done > > on a 512 cpu box. Yes there will be overheads. However it's always possible to create local DoS with some other kind of busy loop? Thanks, Fengguang -- 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
