Messages in this thread | | | Date | Thu, 4 Nov 2004 08:13:37 -0600 | From | Jack Steiner <> | Subject | Re: Externalize SLIT table |
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On Thu, Nov 04, 2004 at 10:59:08AM +0900, Takayoshi Kochi wrote: > Hi, > > For wider audience, added LKML. > > From: Jack Steiner <steiner@sgi.com> > Subject: Externalize SLIT table > Date: Wed, 3 Nov 2004 14:56:56 -0600 > > > The SLIT table provides useful information on internode > > distances. Has anyone considered externalizing this > > table via /proc or some equivalent mechanism. > > > > For example, something like the following would be useful: > > > > # cat /proc/acpi/slit > > 010 066 046 066 > > 066 010 066 046 > > 046 066 010 020 > > 066 046 020 010 > > > > If this looks ok (or something equivalent), I'll generate a patch.... > > For user space to manipulate scheduling domains, pinning processes > to some cpu groups etc, that kind of information is very useful! > Without this, users have no notion about how far between two nodes. > > But ACPI SLIT table is too arch specific (ia64 and x86 only) and > user-visible logical number and ACPI proximity domain number is > not always identical. > > Why not export node_distance() under sysfs? > I like (1). > > (1) obey one-value-per-file sysfs principle > > % cat /sys/devices/system/node/node0/distance0 > 10 > % cat /sys/devices/system/node/node0/distance1 > 66
I'm not familar with the internals of sysfs. For example, on a 256 node system, there will be 65536 instances of /sys/devices/system/node/node<M>/distance<N>
Does this require any significant amount of kernel resources to maintain this amount of information.
> > (2) one distance for each line > > % cat /sys/devices/system/node/node0/distance > 0:10 > 1:66 > 2:46 > 3:66 > > (3) all distances in one line like /proc/<PID>/stat > > % cat /sys/devices/system/node/node0/distance > 10 66 46 66 >
I like (3) the best.
I think it would also be useful to have a similar cpu-to-cpu distance metric: % cat /sys/devices/system/cpu/cpu0/distance 10 20 40 60
This gives the same information but is cpu-centric rather than node centric.
-- Thanks
Jack Steiner (steiner@sgi.com) 651-683-5302 Principal Engineer SGI - Silicon Graphics, Inc.
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