On Tue, Apr 14, 2015 at 11:00:52AM -0400, Przemek Klosowski wrote: > On 04/13/2015 11:34 PM, Zbigniew Jędrzejewski-Szmek wrote: > >OK, so swap 2x memory seems excessive. Actually swap with the same as > >memory should work *most* of the time. There's no guarantee that any > >amount swap will be enough, since it could all be filled by the time > >hibernation is requested, but we should try to cover most normal > >usage. But considering that swap will be slow on HDD, so users will > >most likely avoid using more than a small amount, and SDD are small, > >so it's expensive to provide bigger swap, the default that anaconda > >uses seems OK. An exception is for computers with small amount of RAM > >(<= 2GB?). There swaps is more likely to be filled and the default > >size for swap should imho be higher than the amount of RAM. > Exactly! remember that a typical disk speed is few tens of MB/s, > i.e. about 1 GB/min. I came to the conclusion that anything more > than 4GB is just counterproductive. Large swap just deceives us into > thinking that we can run jobs larger than the physical memory but > that is really not the case, just like Seymour Cray said [1]. The amount of swap space used should be controlled by vm.swappiness sysctl and kernel algorithms, not by making the swap small.
> Maybe swap space should simply be max(4GB, $PhysicalMemory). > Actually, isn't 'swap to filesystem' still an option? if so, maybe > swap should be a constant 4GB, and hibernation should create an > appropriately sized file on the fly, join it to the swap and use > both. I think it should be other way around: swap partition big enough to hibernate, i.e. the size of RAM, and a dynamnically sized swap file if more swap space is needed for non-hibernation data. Zbyszek -- devel mailing list devel@lists.fedoraproject.org https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
