Hi Tigran, > The modern CPUs trying to be too smart. > > try to run this code to disable CPUs c-states: > > ----> setcpulatency.c > > #include <stdio.h> > #include <fcntl.h> > #include <stdint.h> > > int main(int argc, char **argv) { > int32_t l; > int fd; > > if (argc != 2) { > fprintf(stderr, "Usage: %s <latency in us>\n", argv[0]); > return 2; > } > > l = atoi(argv[1]); > printf("setting latency to %d us\n", l); > fd = open("/dev/cpu_dma_latency", O_WRONLY); > if (fd < 0) { > perror("open /dev/cpu_dma_latency"); > return 1; > } > > if (write(fd, &l, sizeof(l)) != sizeof(l)) { > perror("write to /dev/cpu_dma_latency"); > return 1; > } > > while (1) pause(); > } > > > ——> > your C code should be equivalent to the following: echo 0 > /dev/cpu_dma_latency Right? I executed the above command but time execution increase of about 2 seconds over 129seconds (I’ve executed the transaction several times repeating the procedure of restarting db and redoing transaction). With setting echo 1 > /dev/cpu_dma_latency it returns to 129seconds.
> you can use i7z (https://code.google.com/p/i7z/) to see the percentage of CPU > power to be used. I’ve installed i7z-GUI but it reports the following and crashes with segmentation fault (T420 has Intel Xeon, not i-series): i7z DEBUG: i7z version: svn-r77-(20-Nov-2011) i7z DEBUG: Found Intel Processor i7z DEBUG: Stepping 4 i7z DEBUG: Model e i7z DEBUG: Family 6 i7z DEBUG: Processor Type 0 i7z DEBUG: Extended Model 3 i7z DEBUG: msr = Model Specific Register i7z DEBUG: detected a newer model of ivy bridge processor i7z DEBUG: my coder doesn't know about it, can you send the following info to him? i7z DEBUG: model e, extended model 3, proc_family 6 i7z DEBUG: msr device files DONOT exist, trying out a makedev script i7z DEBUG: modprobbing for msr [1]+ Segmentation fault (core dumped) i7z_GUI > Changing CPU from C1 to C0 takes quite some time and for DB workload not > optimal (if you need a > high throughout and any given moment). > > I see ~65% boost when run './setcpulatency 0'. > > Tigran. > With “takes quite some time” you mean that it will take some time to take effect? Thank you a lot for your help. Best regards, Pietro