Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 15 Apr 2010 16:32:19 +1000 | From | Dave Chinner <> | Subject | Re: [PATCH] mm: disallow direct reclaim page writeback |
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On Thu, Apr 15, 2010 at 01:35:17PM +0900, KOSAKI Motohiro wrote: > > Hi > > > > > How about this? For now, we stop direct reclaim from doing writeback > > > only on order zero allocations, but allow it for higher order > > > allocations. That will prevent the majority of situations where > > > direct reclaim blows the stack and interferes with background > > > writeout, but won't cause lumpy reclaim to change behaviour. > > > This reduces the scope of impact and hence testing and validation > > > the needs to be done. > > > > Tend to agree. but I would proposed slightly different algorithm for > > avoind incorrect oom. > > > > for high order allocation > > allow to use lumpy reclaim and pageout() for both kswapd and direct reclaim > > > > for low order allocation > > - kswapd: always delegate io to flusher thread > > - direct reclaim: delegate io to flusher thread only if vm pressure is low > > > > This seems more safely. I mean Who want see incorrect oom regression? > > I've made some pathes for this. I'll post it as another mail. > > Now, kernel compile and/or backup operation seems keep nr_vmscan_write==0. > Dave, can you please try to run your pageout annoying workload?
It's just as easy for you to run and observe the effects. Start with a VM with 1GB RAM and a 10GB scratch block device:
# mkfs.xfs -f /dev/<blah> # mount -o logbsize=262144,nobarrier /dev/<blah> /mnt/scratch
in one shell:
# while [ 1 ]; do dd if=/dev/zero of=/mnt/scratch/foo bs=1024k ; done
in another shell, if you have fs_mark installed, run:
# ./fs_mark -S0 -n 100000 -F -s 0 -d /mnt/scratch/0 -d /mnt/scratch/1 -d /mnt/scratch/3 -d /mnt/scratch/2 &
otherwise run a couple of these in parallel on different directories:
# for i in `seq 1 1 100000`; do echo > /mnt/scratch/0/foo.$i ; done
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
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