On 08/09/2007 12:55 PM, Andrew Morton wrote: > On Thu, 9 Aug 2007 11:59:43 +0200 Matthias Hensler <[EMAIL PROTECTED]> wrote: > >> On Sat, Aug 04, 2007 at 10:44:26AM +0200, Matthias Hensler wrote: >>> On Fri, Aug 03, 2007 at 11:34:07AM -0700, Andrew Morton wrote: >>> [...] >>> I am also willing to try the patch posted by Richard. >> I want to give some update here: >> >> 1. We finally hit the problem on a third system, with a total different >> setup and hardware. However, again high I/O load caused the problem >> and the affected filesystems were mounted with noatime. >> >> 2. I installed a recompiled kernel with just the two line patch from >> Richard Kennedy (http://lkml.org/lkml/2007/8/2/89). That system has 5 >> days uptime now and counting. I believe the patch fixed the problem. >> However, I will continue running "vmstat 1" and the endless loop of >> "cat /proc/meminfo", just in case I am wrong. >> > > Did we ever see the /proc/meminfo and /proc/vmstat output during the stall? > > If Richard's patch has indeed fixed it then this confirms that we're seeing > contention over the dirty-memory limits. Richard's patch isn't really the > right one because it allows unlimited dirty-memory windup in some situations > (large number of disks with small writes, or when we perform queue congestion > avoidance). > > As you're seeing this happening when multiple disks are being written to it is > possible that the per-device-dirty-threshold patches which recently went into > -mm (and which appear to have a bug) will fix it. > > But I worry that the stall appears to persist *forever*. That would indicate > that we have a dirty-memory accounting leak, or that for some reason the > system has decided to stop doing writeback to one or more queues (might be > caused by an error in a lower-level driver's queue congestion state > management). > > If it is the latter, then it could be that running "sync" will clear the > problem. Temporarily, at least. Because sync will ignore the queue > congestion > state. >
This is still a problem for people, and no fix is in sight until 2.6.24. Can we get some kind of band-aid, like making the endless 'for' loop in balance_dirty_pages() terminate after some number of iterations? Clearly if we haven't written "write_chunk" pages after a few tries, *and* we haven't encountered congestion, there's no point in trying forever... [not even compile tested patch follows] --- mm/page-writeback.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) --- linux-2.6.22.noarch.orig/mm/page-writeback.c +++ linux-2.6.22.noarch/mm/page-writeback.c @@ -208,11 +208,12 @@ static void balance_dirty_pages(struct a long background_thresh; long dirty_thresh; unsigned long pages_written = 0; + int i; unsigned long write_chunk = sync_writeback_pages(); struct backing_dev_info *bdi = mapping->backing_dev_info; - for (;;) { + for (i = 0; ; i++) { struct writeback_control wbc = { .bdi = bdi, .sync_mode = WB_SYNC_NONE, @@ -250,6 +251,8 @@ static void balance_dirty_pages(struct a pages_written += write_chunk - wbc.nr_to_write; if (pages_written >= write_chunk) break; /* We've done our duty */ + if (i >= write_chunk && !wbc.encountered_congestion) + break; /* nothing to write? */ } congestion_wait(WRITE, HZ/10); } - 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/