On Wed, Jan 04, 2012 at 07:21:53PM +0200, Leonid Moiseichuk wrote: > The main idea of Used Memory Meter (UMM) is to provide low-cost interface > for user-space to notify about memory consumption using similar approach /proc/meminfo > does but focusing only on "modified" pages which cannot be fogotten. > > The calculation formula in terms of meminfo looks the following: > UsedMemory = (MemTotal - MemFree - Buffers - Cached - SwapCached) + > (SwapTotal - SwapFree) > It reflects well amount of system memory used in applications in heaps and shared pages. > > Previously (n770..n900) we had lowmem.c [1] which used LSM and did a lot other things, > n9 implementation based on memcg [2] which has own problems, so the proposed variant > I hope is the best one for n9: > - Keeps connections from user space > - When amount of modified pages reaches crossed pointed value for particular connection > makes POLLIN and allow user-space app to read it and react > - Economic as much as possible, so currently its operates if allocation higher than 487 > pages or last check happened 250 ms before > Of course if no allocation happened then no activities performed, use-time > must be not affected. > > Testing results: > - Checkpatch produced 0 warning > - Sparse does not produce warnings > - One check costs ~20 us or less (could be checked with probe=1 insmod) > - One connection costs 20 bytes in kernel-space (see observer structure) for 32-bit variant > - For 10K connections poll update in requested in ~10ms, but for practically device expected > to will have about 10 connections (like n9 has now). > > Known weak points which I do not know how to fix but will if you have a brillian idea: > - Having hook in MM is nasty but MM/shrinker cannot be used there and LSM even worse idea > - If I made > $cat /dev/used_memory > it is produced lines in non-stop mode. Adding position check in umm_read seems doesn not help, > so "head -1 /dev/used_memory" should be used if you need to quick check > - Format of output is USED_PAGES:AVAILABLE_PAGES, primitive but enough for tasks module does > > Tested on ARM, x86-32 and x86-64 with and without CONFIG_SWAP. Seems works in all combinations. > Sorry for wide distributions but list of names were produced by scripts/get_maintainer.pl How does this compare with the lowmemorykiller.c driver from the android developers that is currently in the linux-next tree? thanks, greg k-h -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>