On 09/26/2013 06:28 PM, Srivatsa S. Bhat wrote: > On 09/26/2013 05:10 AM, Andrew Morton wrote: >> On Thu, 26 Sep 2013 04:56:32 +0530 "Srivatsa S. Bhat" <srivatsa.bhat@xxxxxxxxxxxxxxxxxx> wrote: >> >>> Experimental Results: >>> ==================== >>> >>> Test setup: >>> ---------- >>> >>> x86 Sandybridge dual-socket quad core HT-enabled machine, with 128GB RAM. >>> Memory Region size = 512MB. >> >> Yes, but how much power was saved ;) >> > > I don't have those numbers yet, but I'll be able to get them going forward. > Hi, I performed experiments on an IBM POWER 7 machine and got actual power-savings numbers (upto 2.6% of total system power) from this patchset. I presented them at the Kernel Summit but forgot to post them on LKML. So here they are: Hardware-setup: -------------- IBM POWER 7 machine: 4 socket (NUMA), 32 cores, 128GB RAM - 4 NUMA nodes with 32 GB RAM each - Booted with numa=fake=1 and treated them as 4 memory regions Software setup: -------------- Workload: Run modified ebizzy for half an hour, which allocates and frees large quantities of memory frequently. The modified ebizzy touches every allocated page a number of times (4 times) before freeing it up. This ensures that allocating a page in the "wrong" memory region makes it very costly in terms of power-savings, since every allocated page is accessed before getting freed (and accesses cause energy consumption). Thus, with this modified benchmark, sub-optimal MM decisions (in terms of memory power-savings) get magnified and hence become noticeable. Power-savings compared to mainline (3.12-rc4): --------------------------------------------- With this patchset applied, the average power of the system reduced by 2.6% compared to the mainline kernel during the benchmark run. The total system power is an excellent metric for such evaluations, since it brings out the overall power-efficiency of the patchset. (IOW, if the patchset shoots up the CPU or disk power-consumption while causing memory power savings, then the total system power will not show much difference). So these numbers indicate that the patchset performs quite well in reducing the power-consumption of the system as a whole. This is not the most ideal hardware configuration to test on, since I had only 4 memory regions to play with, but this gives a good initial indication of the kind of power savings that can be achieved with this patchset. I am expecting the same patchset to give us power-savings of upto 5% of the total system power on a newer prototype hardware that I have (since it has more memory regions and lower base power consumption). Regards, Srivatsa S. Bhat -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>