Messages in this thread | | | Date | Mon, 9 Mar 2015 22:29:36 +1100 | From | Dave Chinner <> | Subject | Re: [PATCH 4/4] mm: numa: Slow PTE scan rate if migration failures occur |
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On Sun, Mar 08, 2015 at 11:35:59AM -0700, Linus Torvalds wrote: > On Sun, Mar 8, 2015 at 3:02 AM, Ingo Molnar <mingo@kernel.org> wrote: > But: > > > As a second hack (not to be applied), could we change: > > > > #define _PAGE_BIT_PROTNONE _PAGE_BIT_GLOBAL > > > > to: > > > > #define _PAGE_BIT_PROTNONE (_PAGE_BIT_GLOBAL+1) > > > > to double check that the position of the bit does not matter? > > Agreed. We should definitely try that. > > Dave?
As Mel has already mentioned, I'm in Boston for LSFMM and don't have access to the test rig I've used to generate this.
> Also, is there some sane way for me to actually see this behavior on a > regular machine with just a single socket? Dave is apparently running > in some fake-numa setup, I'm wondering if this is easy enough to > reproduce that I could see it myself.
Should be - I don't actually use 500TB of storage to generate this - 50GB on an SSD is all you need from the storage side. I just use a sparse backing file to make it look like a 500TB device. :P
i.e. create an XFS filesystem on a 500TB sparse file with "mkfs.xfs -d size=500t,file=1 /path/to/file.img", mount it on loopback or as a virtio,cache=none device for the guest vm and then use fsmark to generate several million files spread across many, many directories such as:
$ fs_mark -D 10000 -S0 -n 100000 -s 1 -L 32 -d \ /mnt/scratch/0 -d /mnt/scratch/1 -d /mnt/scratch/2 -d \ /mnt/scratch/3 -d /mnt/scratch/4 -d /mnt/scratch/5 -d \ /mnt/scratch/6 -d /mnt/scratch/7
That should only take a few minutes to run - if you throw 8p at it then it should run at >100k files/s being created.
Then unmount and run "xfs_repair -o bhash=101703 /path/to/file.img" on the resultant image file.
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
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