I am beginning to understand why zram appears to work fine on our x86 systems but not on our ARM systems. The bottom line is that swapping doesn't work as I would expect when allocation is "too fast". In one of my tests, opening 50 tabs simultaneously in a Chrome browser on devices with 2 GB of RAM and a zram-disk of 3 GB (uncompressed), I was observing that on the x86 device all of the zram swap space was used before OOM kills happened, but on the ARM device I would see OOM kills when only about 1 GB (out of 3) was swapped out. I wrote a simple program to understand this behavior. The program (called "hog") allocates memory and fills it with a mix of incompressible data (from /dev/urandom) and highly compressible data (1's, just to avoid zero pages) in a given ratio. The memory is never touched again. It turns out that if I don't limit the allocation speed, I see premature OOM kills also on the x86 device. If I limit the allocation to 10 MB/s, the premature OOM kills stop happening on the x86 device, but still happen on the ARM device. If I further limit the allocation speed to 5 Mb/s, the premature OOM kills disappear also from the ARM device. I have noticed a few time constants in the MM whose value is not well explained, and I am wondering if the code is tuned for some ideal system that doesn't behave like ours (considering, for instance, that zram is much faster than swapping to a disk device, but it also uses more CPU). If this is plausible, I am wondering if anybody has suggestions for changes that I could try out to obtain a better behavior with a higher allocation speed. Thanks! Luigi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>