Hi, I was experimenting with the usage of blkio recently and got some interesting results which differed from what the blkio manual describes. Details of the experiment : Type of disk : magnetic Cgroups and weight assigned : 10 cgroups named Group1,Group2..Group10 with 100,200..1000 wight respectively assigned to each group. I created these groups both with cpu and blkio subsystem. The scheduler was set to cfq. Operations Involved : I created 10 files using dd, 40GB each. Now, for the experiment, I was attempting to read sequentially from the files. I used the following command for each group cgexec -g blkio:test/group<id> -g cpu:test/group<id> time dd if=/usr/sumo/ephemeral/katta/test/group<id>/file of=/dev/null bs=1M where id is from 1 to 10.Also, dropped os disk cache before running experiment. Now, I have got results which differ from what I expected. After running the experiment for some time, here are the results : Blkio stats were reset before start of the experiment. Following results represent the cgroup followed by bytes read from t = 0s (start of experiment) to t = 15m . Group1 -> 2.51 G Group2 -> 3.45 G Group3 -> 2.64 G Group4 -> 3.41 G Group5 -> 5.92 G Group6 -> 9.62 G Group7 -> 10.81 G Group8 -> 11.21 G Group9 -> 17.68 G Group10 -> 19.13 G It seems like there is some clustering for the weights greater and less than 500 and bytes read are not proportional to the weights assigned.I have repeated the experiment few times but have been getting same result. My question is : Given that the bytes read were not in ratio of the weights provided, Is this expected behavior ? if not, is it something that I am possibly over looking while performing the experiments? Thanks, Ankur. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
