On Mon, 14 Jun 2010 12:19:55 +0530 Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > > - Why don't you believe LRU ? And if LRU doesn't work well, should it be > > fixed by a knob rather than generic approach ? > > - No side effects ? > > I believe in LRU, just that the problem I am trying to solve is of > using double the memory for caching the same data (consider kvm > running in cache=writethrough or writeback mode, both the hypervisor > and the guest OS maintain a page cache of the same data). As the VM's > grow the overhead is substantial. In my runs I found upto 60% > duplication in some cases. > > > - Linux vm guys tend to say, "free memory is bad memory". ok, for what > free memory created by your patch is used ? IOW, I can't see the benefit. > If free memory that your patch created will be used for another page-cache, > it will be dropped soon by your patch itself. > > Free memory is good for cases when you want to do more in the same > system. I agree that in a bare metail environment that might be > partially true. I don't have a problem with frequently used data being > cached, but I am targetting a consolidated environment at the moment. > Moreover, the administrator has control via a boot option, so it is > non-instrusive in many ways. It sounds that what you want is to improve performance etc. but to make it easy sizing the system and to help admins. Right ? >From performance perspective, I don't see any advantage to drop caches which can be dropped easily. I just use cpus for the purpose it may no be necessary. Thanks, -Kame -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
