Hello, That is a continuation of Used Memory Meter (UMM) started as [1] and re-designed according to inputs I can implement. The main idea of memnotify is to provide low-cost interface for user-space to update with specified granularity and timeout required memory usulization values in specified moment of time. It is not a low memory interface as [2] nor OOM killer but it could be used for situations related to "close-to-OOM" handling. The examples of usage could be discovered in libmemnotify [3] or test case code below this intro. During the previous discussion two biggest disappointments were discovered: 1. hooking MM -- now it is removed, the new solution has 0 MM changes, only extra shrinker added to re-enforce timer to re-check memory situation as soon as possible 2. extendability -- to add any other tracked value you need to modify 2 places in code (memtypes[] and get_memory_status() function). As Kosaki-san said for activity tracking I added "active" page set. You can subscribe for one or several values for tracking simultaneously. To periodic re-read vm_stat (using global_page_state() interface) I use deferred timer, expecting if cpu sleeps timer could be delayed and use-time will be not affected. If this assumption is not correct I can add register_cpu_notifier() call. Otherwise, when no clients connected - no activity or subscription in module performed. The number of module parameters could be specified to adjust reaction time or granularity of changes. The interface pseudo-device hardcoded as /dev/memnotify. As in previous time module tested using arm, x86-32 and x86-64 for typical (10 clients) and stress (10K clients) cases. With Best Regards, Leonid References: 1. https://lkml.org/lkml/2012/1/4/208 2. https://lkml.org/lkml/2012/1/17/34 3. http://maemo.gitorious.org/maemo-tools/libmemnotify Leonid Moiseichuk (2): Making si_swapinfo exportable Memory notification pseudo-device module drivers/misc/Kconfig | 11 + drivers/misc/Makefile | 1 + drivers/misc/memnotify.c | 582 ++++++++++++++++++++++++++++++++++++++++++++++ mm/swapfile.c | 3 + 4 files changed, 597 insertions(+), 0 deletions(-) create mode 100644 drivers/misc/memnotify.c -- 1.7.7.3 /* * mn_test.c - test for system-wide memory notification/meter implementation * * Usage: * $gcc -o mn_test mn_test.c * $mn_test * or with pointing pages as threshold(s) * $mn_test "used 5000" * or * $mn_test "active 8000 used 16000" * * Copyright (C) 2012 Nokia Corporation. * Leonid Moiseichuk * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed "as is" WITHOUT ANY WARRANTY of any * kind, whether express or implied; without even the implied warranty * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. */ #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <stdio.h> #include <poll.h> #include <stdlib.h> #include <unistd.h> #include <string.h> int main(const int argc, const char* argv[]) { const char *dev = "/dev/memnotify"; const int fd = open(dev,O_RDWR); const char *lim = (2 == argc && argv[1] ? argv[1] : NULL); ssize_t ret; struct pollfd fds[1]; char tmp[256]; printf ("%s -- test for system-wide memory notification/meter %s\n", argv[0], dev); if (lim && 0 == strcmp(lim, "--help")) { printf ("usage: %s [threshold(s)_in_pages]\n", argv[0]); printf ("example of threshold(s) available in %s\n", dev); return -1; } if (fd < 0) { printf ("cannot open device %s, do you have memnotify.ko loaded?\n", dev); return -1; } else { printf ("device %s opened successfuly with fd = %d\n", dev, fd); } if ((ret = read(fd, tmp, sizeof(tmp))) < 0) { printf ("reading from %s failed\n", dev); return -1; } tmp[ret - 1] = 0; printf ("read from %s %d bytes: '%s'\n", dev, ret, tmp); /* do we have a threshold? */ if ( !lim ) return 0; printf ("establishing threshold '%s' and waiting\n", lim); if ((ret = write(fd, argv[1], strlen(argv[1]))) < 0) { printf ("cannot set threshold '%s' for device %s\n", lim, dev); return -1; } printf ("polling for threshold '%s' to be changed to up/down\n", lim); fds->fd = fd; fds->events = POLLIN; fds->revents = 0; ret = poll(fds, 1, -1); printf ("poll(%d) returned %d\n", fd, ret); if ((ret = read(fd, tmp, sizeof(tmp))) < 0) { printf ("reading from %s failed\n", dev); return -1; } tmp[ret - 1] = 0; printf ("--> memory figures reached '%s'\n", tmp); return 0; } /* ---< end of mn_test.c >---- */ -- 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>