(switched to email. Please respond via emailed reply-to-all, not via the bugzilla web interface). On Fri, 24 Oct 2014 15:33:02 +0000 bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > https://bugzilla.kernel.org/show_bug.cgi?id=86831 > > Bug ID: 86831 > Summary: wrong count of dirty pages when using AIO > Product: Memory Management > Version: 2.5 > Kernel Version: 3.14.21 > Hardware: All > OS: Linux > Tree: Mainline > Status: NEW > Severity: normal > Priority: P1 > Component: Other > Assignee: akpm@xxxxxxxxxxxxxxxxxxxx > Reporter: m.koenigshaus@xxxxxx > Regression: No > > Hello, > > we use a ARM custom Board with mysqld. Shuting down mysqld (with IAO support, > on a ext3 formatted Harddrive) leads to a negative number of dirty pages > (underrun to the counter). The negative number results in a drastic reduction > of the write performance because the page cache is not used, because the kernel > thinks it is still 2 ^ 32 dirty pages open. I found, the problem is > mm/truncate.c->cancel_dirty_page() > > To reproduce,first change cancel_dirty_page() > > [...] > if (mapping && mapping_cap_account_dirty (mapping)) { > ++WARN_ON ((int) global_page_state(NR_FILE_DIRTY) <0); > dec_zone_page_state (page, NR_FILE_DIRTY); > [...] > > And test -> hm, I wonder what AIO is doing differently - cancel_dirty_page() isn't specific to aio - it's used by all truncations. Just to sanity check, could you please try something like this? --- a/include/linux/vmstat.h~a +++ a/include/linux/vmstat.h @@ -241,6 +241,8 @@ static inline void __inc_zone_state(stru static inline void __dec_zone_state(struct zone *zone, enum zone_stat_item item) { atomic_long_dec(&zone->vm_stat[item]); + WARN_ON_ONCE(item == NR_FILE_DIRTY && + atomic_long_read(&zone->vm_stat[item]) < 0); atomic_long_dec(&vm_stat[item]); } That should catch the first offending decrement, although yes, it's probably cancel_dirty_page(). (This assumes you're using an SMP kernel. If not, mm/vmstat.c:dec_zone_page_state() will need to be changed instead) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>