* KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-06-11 14:05:53]: > On Fri, 11 Jun 2010 10:16:32 +0530 > Balbir Singh <balbir@xxxxxxxxxxxxxxxxxx> wrote: > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> [2010-06-11 10:54:41]: > > > > > On Thu, 10 Jun 2010 17:07:32 -0700 > > > Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > > On Thu, 2010-06-10 at 19:55 +0530, Balbir Singh wrote: > > > > > > I'm not sure victimizing unmapped cache pages is a good idea. > > > > > > Shouldn't page selection use the LRU for recency information instead > > > > > > of the cost of guest reclaim? Dropping a frequently used unmapped > > > > > > cache page can be more expensive than dropping an unused text page > > > > > > that was loaded as part of some executable's initialization and > > > > > > forgotten. > > > > > > > > > > We victimize the unmapped cache only if it is unused (in LRU order). > > > > > We don't force the issue too much. We also have free slab cache to go > > > > > after. > > > > > > > > Just to be clear, let's say we have a mapped page (say of /sbin/init) > > > > that's been unreferenced since _just_ after the system booted. We also > > > > have an unmapped page cache page of a file often used at runtime, say > > > > one from /etc/resolv.conf or /etc/passwd. > > > > > > > > > > Hmm. I'm not fan of estimating working set size by calculation > > > based on some numbers without considering history or feedback. > > > > > > Can't we use some kind of feedback algorithm as hi-low-watermark, random walk > > > or GA (or somehing more smart) to detect the size ? > > > > > > > Could you please clarify at what level you are suggesting size > > detection? I assume it is outside the OS, right? > > > "OS" includes kernel and system programs ;) > > I can think of both way in kernel and in user approarh and they should be > complement to each other. > > An example of kernel-based approach is. > 1. add a shrinker callback(A) for balloon-driver-for-guest as guest kswapd. > 2. add a shrinker callback(B) for balloon-driver-for-host as host kswapd. > (I guess current balloon driver is only for host. Please imagine.) > > (A) increases free memory in Guest. > (B) increases free memory in Host. > > This is an example of feedback based memory resizing between host and guest. > > I think (B) is necessary at least before considering complecated things. B is left to the hypervisor and the memory policy running on it. My patches address Linux running as a guest, with a Linux hypervisor at the moment, but that can be extended to other balloon drivers as well. > > To implement something clever, (A) and (B) should take into account that > how frequently memory reclaim in guest (which requires some I/O) happens. > Yes, I think the policy in the hypervisor needs to look at those details as well. > If doing outside kernel, I think using memcg is better than depends on > balloon driver. But co-operative balloon and memcg may show us something > good. > Yes, agreed. Co-operative is better, if there is no co-operation than memcg might be used for enforcement. -- Three Cheers, Balbir -- 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
