Messages in this thread | | | Date | Thu, 19 Nov 2009 07:43:02 +0100 | From | Tomasz Chmielewski <> | Subject | Re: Linux 2.6.31 - very swap-happy with plenty of free RAM |
| |
Dave Chinner wrote:
>>>> I have a pretty powerful desktop machine with 8 GB RAM, fast disks with >>>> RAID-1 etc. >>>> Every 10 minutes or so, machine is really unresponsive, load jumps to 10 or >>>> 20. Mouse pointer jumps, it's impossible to change between windows etc. >>> This is the type of hefty workstation many of the core developers >>> have, running similar workloads, so I'm somewhat surprised that the >>> default VM settings have this kind of issue. >>> >>>> Do a "swapoff -a", and everything is snappy and responsive as it should, >>>> there are no more lags. >>> Yes, that's my exact finding. >>> >>> Is this weird IO storm happening for anyone else with plenty of memory >>> (for their taskload?) >> For me it happend on my laptop. 3gb RAM, and a 1gb VMWare Windows-XP >> instance running, plus the usual like firefox, thunderbird, kde4. >> >> Without running vmware it did not happen. And since I have now disabled >> barriers on the xfs /home partition (on luks crypto lvm) it also does >> not happen anymore. > > Yeah, it looks like dm-crypt recently started supporting barriers in > commit 647c7db14ef9cacc4ccb3683e206b61f0de6dc2b. Hence XFS will have > detected barriers work at mount time mount and so is now issuing > them. > > Similarly, raid1 (mirror) has recently gained barrier support so > the same issue can be seen there.
What is also interesting, that a normal software RAID-1 sync (i.e. from a degraded state) does not seem to make any visible effect on system responsiveness.
Uncompress a big tar file, or VM writes out lots of data - system becomes really unresponsive.
-- Tomasz Chmielewski http://wpkg.org
| |