Hi all, I've been wondering this for some time (i.e. a good 5 years or so, never had the time to go sit down and nut it out). I haven't worried about it since it normally is just a minor nit, but today I was doing something where I really did need swap to work. On i386 systems I used to allocate a *HUGE* swap partition and mount tmpfs on /tmp. This used to work really well, swap usage would grow as I plonk files in /tmp, and when I reboot, it'd be nice and clean ready to go. When I tried this on AMD64, I found this no longer worked as expected. Swap would be left alone, and sometimes RAM would become scarce once too many files were deposited in /tmp. This has been the case for me ever since I got my first AMD64 machine (mid-2010). Today, I was busy slicing up images for printing in The Gimp. One that has been giving me curry is this one: https://publications.qld.gov.au/dataset/guide-to-queensland-roads/resource/f86c19ae-9adf-4100-bb59-5113548c361e I rasterise that at 1440 DPI, then try to crop or print it. I have 8GB RAM and my swap partition is 10GB. Inspite of this, I'm not seeing more than about 200MB of swap space used at any time, and The Gimp crawls. Not surprising that it's slow as I really need 16GB to process something this size, but it is surprising that the 10GB of swap doesn't get touched: > RC=0 stuartl@vk4msl-mb ~ $ free > total used free shared buffers cached > Mem: 7915412 7684668 230744 6804 19264 2073856 > -/+ buffers/cache: 5591548 2323864 > Swap: 10664956 197432 10467524 > RC=0 stuartl@vk4msl-mb ~ $ uname -a > Linux vk4msl-mb 3.16.2-vk4msl-mb #1 SMP PREEMPT Fri Sep 12 22:32:47 EST 2014 x86_64 Intel(R) Core(TM)2 Duo CPU P7350 @ 2.00GHz GenuineIntel GNU/Linux I run vanilla kernels that I build myself and most of the settings come from defconfig. I can post my .config if people desire. Until today I have not touched 'swappiness' (today I tried setting it to 80). Is there some setting I've missed in .config that allows swap to be utilised on AMD64? -- Stuart Longland (aka Redhatter, VK4MSL) I haven't lost my mind... ...it's backed up on a tape somewhere. -- To unsubscribe from this list: send the line "unsubscribe linux-admin" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
