[lkml]   [2007]   [Jan]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [REGRESSION] 2.6.19/2.6.20-rc3 buffered write slowdown
David Chinner wrote:
> On Thu, Jan 11, 2007 at 12:08:10PM +1100, Nick Piggin wrote:

>>>So, what I've attached is three files which have both
>>>'vmstat 5' output and 'iostat 5 |grep dm-' output in them.
>>Ahh, sorry to be unclear, I meant:
>> cat /proc/vmstat > pre
>> run_test
>> cat /proc/vmstat > post
> Ok, I'll get back to you on that one - even at 600+MB/s, writing 5TB
> of data takes some time....

OK, according to your vmstat deltas, you are doing an order of magnitude
more writeout off the LRU with 2.6.20-rc3 default than with the smaller
dirty_ratio (53GB of data vs 4GB of data). 2.6.18 does not have that stat,

allocstall and direct reclaim are way down when the dirty ratio is lower,
but those numbers with vanilla 2.6.20-rc3 are comparable to 2.6.18, so
that shows that kswapd in 2.6.18 is probably also having trouble which may
mean it is also writing out a lot off the LRU.

You're not turning on zone_reclaim, by any chance, are you?

Otherwise, nothing jumps out at me yet. I'll have a bit of a look through
changelogs tomorrow. I guess it could be a pdflush or vmscan change (XFS,

Can you narrow it down at all?


SUSE Labs, Novell Inc.
Send instant messages to your online friends

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2007-01-11 10:55    [W:0.093 / U:5.664 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site