On Thu, Sep 03, 2009 at 11:24:23AM +0900, Ryo Tsuruta wrote: > Hi Vivek, > > Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > > > > > > - Somebody also gave an example where there is a memory hogging process and > > > > > > > possibly pushes out some processes to swap. It does not sound fair to > > > > > > > charge those proccess for that swap writeout. These processes never > > > > > > > requested swap IO. > > > > > > > > > > I think that swap writeouts should be charged to the memory hogging > > > > > process, because the process consumes more resources and it should get > > > > > a penalty. > > > > > > > > > > > > > A process requesting memory gets IO penalty? IMHO, swapping is a kernel > > > > mechanism and kernel's way of providing extended RAM. If we want to solve > > > > the issue of memory hogging by a process then right way to solve is to use > > > > memory controller and not by charging the process for IO activity. > > > > Instead, proabably a more suitable way is to charge swap activity to root > > > > group (where by default all the kernel related activity goes). > > > > > > No. In the current blkio-cgroup, a process which uses a large amount > > > of memory gets penalty, not a memory requester. > > > > > > > At ioband level you just get to see bio and page. How do you decide wheter > > this bio is being issued by a process which is a memory hog? > > > > In fact requester of memory could be anybody. It could be memory hog or a > > different process. So are you saying that you got a mechanism where you > > can detect that a process is memory hog and charge swap activity to it. > > IOW, if there are two processes A and B and assume A is the memory hog and > > then B requests for memory which triggers lot of swap IO, then you can > > charge all that IO to memory hog A? > > When an annoymou page is allocated, blkio-cgroup sets an ID to the > page. And then when the page is going to swap out, dm-ioband can know > who the owner of the page is by retrieving ID from the page. > > In the above case, since the pages of the process A are swapped-out, > dm-ioband charges swap IO to the process A. > But this does not mean that in all cases memory hog is being charged for swap IO, as you have said. So if a process A has done some anonymous page allocations and later a memory hog B comes in and forces swap out of A, you will charge A for swap activity which does not seem fair as B is memory hog here? Thanks Vivek > > Can you please point me to the relevant code in dm-ioband? > > > > IMHO, to keep things simple, all swapping activity should be charged to > > root group and be considered as kernel activity and user space not be > > charged for that. > > Thanks, > Ryo Tsuruta -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
