Izik Eidus wrote: > Anthony Liguori wrote: >> Izik Eidus wrote: >>> this patchs allow the guest not shadowed memory to be swapped out. >>> >>> to make it the must effective you should run -kvm-shadow-memory 1 >>> (witch will make your machine slow) >>> with -kvm-shadow-memory 1, 3giga memory guest can get to be just >>> 32mb on physical host! >>> >>> when not using -kvm-shadow-memory, i saw 4100mb machine getting to >>> as low as 168mb on the physical host (not as bad as i thought it >>> would be, and surely not as bad as it can be with 41mb of shadow >>> pages :)) >>> >> >> So what exactly does this option do? Is it really worth exposing it >> as an option if it slows down guests so much? >> >> At least, a better name for the option would be nice. >> >> Regards, >> >> Anthony Liguori > -kvm-shadow-memory was included in kvm from version 46. > it control how much pages will be allocated to the shadow cache, (from > version 46 the default is 2% of the system (so 4.1giga have about 80 > mbs of shadow cache by default)) > the problem is that each page that present at the shadow cache ( mmu > pages ) cant be swapped out, so as lower as the number of shadow > caches you have as more swappable will be > useful. > > (this option (kvm-shadow-memory) was included to make it possible that > as less as possible shadow cache memory will be deleated ( beacuse it > have big overhead to lose this cache) > just to make it clearer, -kvm-shadow-memory main purpose is to speed up the guest, ( as more mmu pages you have to the shadow cache, as faster as your guest will be while it working with alot of memory) (the main mission is that kvm_free_some_pages() will get called as less as possible)
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