Dear Christopher, Thanks for the hint about the BIOS. I updated it, the BIOS version went from 2.2.1 to 2.4.0. With the new BIOS and running non-PAE kernel: psz@DellE520:~$ uname -a Linux DellE520 3.2.0-51-generic #77-Ubuntu SMP Wed Jul 24 20:21:10 UTC 2013 i686 i686 i386 GNU/Linux psz@DellE520:~$ free -l total used free shared buffers cached Mem: 3087960 1128504 1959456 0 152800 705708 Low: 861452 213880 647572 High: 2226508 914624 1311884 -/+ buffers/cache: 269996 2817964 Swap: 20000920 0 20000920 it handled the "sleep test" bash -c 'n=0; while [ $n -lt 33000 ]; do sleep 600 & ((n=n+1)); ((m=n%500)); if [ $m -lt 1 ]; then echo -n "$n - "; date; free -l; sleep 1; fi; done' just fine (as expected), running out of "max user processes" because of default setting of "ulimit -u 23964". Installing the PAE kernel and rebooting (of course with new BIOS): psz@DellE520:~$ uname -a Linux DellE520 3.2.0-51-generic-pae #77-Ubuntu SMP Wed Jul 24 20:40:32 UTC 2013 i686 i686 i386 GNU/Linux psz@DellE520:~$ free -l total used free shared buffers cached Mem: 3087592 610740 2476852 0 112796 344216 Low: 865180 160496 704684 High: 2222412 450244 1772168 -/+ buffers/cache: 153728 2933864 Swap: 20000920 0 20000920 (has default setting "ulimit -u 23960") and re-trying the "sleep test", things went bad after 22500 processes. The graphics console crashed, with X saying "your graphics device is running in low-resolution mode" or somesuch, and with no mouse or keyboard response so could not click the OK button. Hitting Alt-Ctrl-F2 worked and got a getty login. Looking with ps, there were no sleep processes left running. In /var/log/syslog I found: Aug 8 20:01:48 DellE520 kernel: [ 341.000570] oom_kill_process: 39 callbacks suppressed Aug 8 20:01:48 DellE520 kernel: [ 341.000578] bash invoked oom-killer: gfp_mask=0x84d0, order=0, oom_adj=0, oom_score_adj=0 Aug 8 20:01:48 DellE520 kernel: [ 341.000584] bash cpuset=/ mems_allowed=0 Aug 8 20:01:48 DellE520 kernel: [ 341.000589] Pid: 2375, comm: bash Not tainted 3.2.0-51-generic-pae #77-Ubuntu Aug 8 20:01:48 DellE520 kernel: [ 341.000593] Call Trace: Aug 8 20:01:48 DellE520 kernel: [ 341.000605] [] dump_header.isra.6+0x85/0xc0 Aug 8 20:01:48 DellE520 kernel: [ 341.000612] [] oom_kill_process+0x5c/0x80 Aug 8 20:01:48 DellE520 kernel: [ 341.000617] [] out_of_memory+0xc5/0x1c0 Aug 8 20:01:48 DellE520 kernel: [ 341.000623] [] __alloc_pages_nodemask+0x72c/0x740 Aug 8 20:01:48 DellE520 kernel: [ 341.000630] [] __get_free_pages+0x1c/0x30 Aug 8 20:01:48 DellE520 kernel: [ 341.000636] [] pgd_alloc+0x74/0x250 Aug 8 20:01:48 DellE520 kernel: [ 341.000642] [] ? place_entity+0x9a/0x160 Aug 8 20:01:48 DellE520 kernel: [ 341.000648] [] mm_init+0xc7/0x100 Aug 8 20:01:48 DellE520 kernel: [ 341.000653] [] dup_mm+0xa3/0x230 Aug 8 20:01:48 DellE520 kernel: [ 341.000658] [] copy_process.part.23+0x71d/0xc10 Aug 8 20:01:48 DellE520 kernel: [ 341.000663] [] copy_process+0x7e/0x90 Aug 8 20:01:48 DellE520 kernel: [ 341.000668] [] do_fork+0xf4/0x2c0 Aug 8 20:01:48 DellE520 kernel: [ 341.000675] [] sys_clone+0x34/0x40 Aug 8 20:01:48 DellE520 kernel: [ 341.000682] [] ptregs_clone+0x15/0x3c Aug 8 20:01:48 DellE520 kernel: [ 341.000687] [] ? sysenter_do_call+0x12/0x28 Aug 8 20:01:48 DellE520 kernel: [ 341.000691] Mem-Info: Aug 8 20:01:48 DellE520 kernel: [ 341.000694] DMA per-cpu: Aug 8 20:01:48 DellE520 kernel: [ 341.000699] CPU 0: hi: 0, btch: 1 usd: 0 Aug 8 20:01:48 DellE520 kernel: [ 341.000702] CPU 1: hi: 0, btch: 1 usd: 0 Aug 8 20:01:48 DellE520 kernel: [ 341.000705] Normal per-cpu: Aug 8 20:01:48 DellE520 kernel: [ 341.000708] CPU 0: hi: 186, btch: 31 usd: 0 Aug 8 20:01:48 DellE520 kernel: [ 341.000711] CPU 1: hi: 186, btch: 31 usd: 29 Aug 8 20:01:48 DellE520 kernel: [ 341.000714] HighMem per-cpu: Aug 8 20:01:48 DellE520 kernel: [ 341.000717] CPU 0: hi: 186, btch: 31 usd: 0 Aug 8 20:01:48 DellE520 kernel: [ 341.000720] CPU 1: hi: 186, btch: 31 usd: 167 Aug 8 20:01:48 DellE520 kernel: [ 341.000726] active_anon:326331 inactive_anon:81629 isolated_anon:0 Aug 8 20:01:48 DellE520 kernel: [ 341.000728] active_file:11586 inactive_file:8659 isolated_file:0 Aug 8 20:01:48 DellE520 kernel: [ 341.000729] unevictable:0 dirty:0 writeback:2 unstable:0 Aug 8 20:01:48 DellE520 kernel: [ 341.000730] free:25897 slab_reclaimable:2285 slab_unreclaimable:60037 Aug 8 20:01:48 DellE520 kernel: [ 341.000732] mapped:14875 shmem:32942 pagetables:111532 bounce:0 Aug 8 20:01:48 DellE520 kernel: [ 341.000740] DMA free:4108kB min:784kB low:980kB high:1176kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15788kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:3432kB kernel_stack:2680kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? yes Aug 8 20:01:48 DellE520 kernel: [ 341.000747] lowmem_reserve[]: 0 869 3022 3022 Aug 8 20:01:48 DellE520 kernel: [ 341.000759] Normal free:44060kB min:44216kB low:55268kB high:66324kB active_anon:0kB inactive_anon:0kB active_file:232kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:890008kB mlocked:0kB dirty:0kB writeback:0kB mapped:4kB shmem:0kB slab_reclaimable:9140kB slab_unreclaimable:236716kB kernel_stack:182208kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:426 all_unreclaimable? yes Aug 8 20:01:48 DellE520 kernel: [ 341.000766] lowmem_reserve[]: 0 0 17226 17226 Aug 8 20:01:48 DellE520 kernel: [ 341.000778] HighMem free:55420kB min:512kB low:27900kB high:55288kB active_anon:1305324kB inactive_anon:326516kB active_file:46112kB inactive_file:34636kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2205048kB mlocked:0kB dirty:0kB writeback:8kB mapped:59496kB shmem:131768kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:446128kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:16 all_unreclaimable? no Aug 8 20:01:48 DellE520 kernel: [ 341.000785] lowmem_reserve[]: 0 0 0 0 Aug 8 20:01:48 DellE520 kernel: [ 341.000792] DMA: 3*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 2*2048kB 0*4096kB = 4108kB Aug 8 20:01:48 DellE520 kernel: [ 341.000808] Normal: 83*4kB 118*8kB 88*16kB 41*32kB 28*64kB 19*128kB 14*256kB 15*512kB 8*1024kB 6*2048kB 1*4096kB = 44060kB Aug 8 20:01:48 DellE520 kernel: [ 341.000825] HighMem: 37*4kB 55*8kB 45*16kB 97*32kB 37*64kB 16*128kB 10*256kB 8*512kB 7*1024kB 2*2048kB 7*4096kB = 55420kB Aug 8 20:01:48 DellE520 kernel: [ 341.000841] 53204 total pagecache pages Aug 8 20:01:48 DellE520 kernel: [ 341.000844] 25 pages in swap cache Aug 8 20:01:48 DellE520 kernel: [ 341.000847] Swap cache stats: add 1064, delete 1039, find 0/0 Aug 8 20:01:48 DellE520 kernel: [ 341.000850] Free swap = 19996668kB Aug 8 20:01:48 DellE520 kernel: [ 341.000852] Total swap = 20000920kB Aug 8 20:01:48 DellE520 kernel: 0 sleep Aug 8 20:01:48 DellE520 kernel: [ 341.114879] [23879] 1000 23879 537 70 0 0 0 sleep Aug 8 20:01:48 DellE520 kernel: [ 341.114884] [23880] 1000 23880 537 70 0 0 0 sleep ... [ many lines dropped] ... Aug 8 20:01:58 DellE520 kernel: [ 343.218430] [25435] 1000 25435 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218435] [25436] 1000 25436 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218440] [25437] 0 25437 558 72 1 0 0 sh Aug 8 20:01:58 DellE520 kernel: [ 343.218445] [25438] 1000 25438 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218450] [25439] 1000 25439 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218455] [25440] 1000 25440 537 71 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218460] [25441] 1000 25441 1240 279 0 0 0 dbus-daemon Aug 8 20:01:58 DellE520 kernel: [ 343.218465] [25442] 1000 25442 104 1 0 0 0 gconfd-2 Aug 8 20:01:58 DellE520 kernel: [ 343.218470] [25443] 1000 25443 537 71 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218475] [25444] 1000 25444 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218480] [25445] 1000 25445 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218485] [25446] 1000 25446 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218490] [25447] 1000 25447 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218495] [25448] 1000 25448 537 71 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218500] [25449] 1000 25449 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218505] [25450] 1000 25450 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218510] [25451] 1000 25451 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218515] [25452] 1000 25452 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218520] [25453] 1000 25453 537 71 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218525] [25454] 1000 25454 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218530] [25455] 0 25455 558 71 1 0 0 sh Aug 8 20:01:58 DellE520 kernel: [ 343.218535] [25456] 1000 25456 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218540] [25457] 0 25457 915 270 1 0 0 init Aug 8 20:01:58 DellE520 kernel: [ 343.218545] [25458] 1000 25458 537 71 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218550] [25459] 1000 25459 537 71 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218555] [25460] 1000 25460 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218560] [25461] 1000 25461 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218565] [25462] 1000 25462 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218570] [25463] 1000 25463 537 70 0 0 0 sleep Aug 8 20:01:58 DellE520 kernel: [ 343.218575] Out of memory: Kill process 1369 (nmbd) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.218581] Killed process 1369 (nmbd) total-vm:13320kB, anon-rss:580kB, file-rss:936kB Aug 8 20:01:58 DellE520 kernel: [ 343.262519] Out of memory: Kill process 1468 (getty) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.262528] Killed process 1468 (getty) total-vm:4628kB, anon-rss:124kB, file-rss:732kB Aug 8 20:01:58 DellE520 kernel: [ 343.295863] Out of memory: Kill process 1475 (getty) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.295871] Killed process 1475 (getty) total-vm:4628kB, anon-rss:116kB, file-rss:732kB Aug 8 20:01:58 DellE520 kernel: [ 343.327243] Out of memory: Kill process 1487 (getty) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.327252] Killed process 1487 (getty) total-vm:4628kB, anon-rss:128kB, file-rss:732kB Aug 8 20:01:58 DellE520 kernel: [ 343.407546] Out of memory: Kill process 1490 (getty) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.407554] Killed process 1490 (getty) total-vm:4628kB, anon-rss:120kB, file-rss:732kB Aug 8 20:01:58 DellE520 kernel: [ 343.439427] Out of memory: Kill process 1498 (getty) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.439435] Killed process 1498 (getty) total-vm:4628kB, anon-rss:120kB, file-rss:732kB Aug 8 20:01:58 DellE520 kernel: [ 343.467474] Out of memory: Kill process 1531 (acpid) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.467482] Killed process 1531 (acpid) total-vm:2172kB, anon-rss:180kB, file-rss:500kB Aug 8 20:01:58 DellE520 kernel: [ 343.499479] Out of memory: Kill process 1533 (cron) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.499487] Killed process 1533 (cron) total-vm:2616kB, anon-rss:172kB, file-rss:692kB Aug 8 20:01:58 DellE520 kernel: [ 343.531335] Out of memory: Kill process 1535 (atd) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.531343] Killed process 1535 (atd) total-vm:2468kB, anon-rss:128kB, file-rss:220kB Aug 8 20:01:58 DellE520 kernel: [ 343.563656] Out of memory: Kill process 1567 (Xorg) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.563663] Killed process 1567 (Xorg) total-vm:144576kB, anon-rss:11564kB, file-rss:7052kB Aug 8 20:01:58 DellE520 kernel: [ 343.882488] Out of memory: Kill process 1714 (getty) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 343.882497] Killed process 1714 (getty) total-vm:4628kB, anon-rss:124kB, file-rss:732kB Aug 8 20:01:58 DellE520 kernel: [ 344.154510] Out of memory: Kill process 2007 (lightdm) score 1 or sacrifice child Aug 8 20:01:58 DellE520 kernel: [ 344.154519] Killed process 2007 (lightdm) total-vm:25928kB, anon-rss:1028kB, file-rss:4316kB Aug 8 20:01:58 DellE520 kernel: [ 344.303301] init: Disconnected from system bus Aug 8 20:01:58 DellE520 kernel: [ 344.304586] init: cups main process (1096) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 344.304629] init: cups main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 344.304924] init: nmbd main process (1369) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 344.304962] init: nmbd main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 344.305190] init: tty4 main process (1468) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 344.305228] init: tty4 main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 344.768077] init: tty5 main process (1475) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 344.768125] init: tty5 main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 345.173773] init: tty2 main process (1487) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 345.173823] init: tty2 main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 345.174086] init: tty3 main process (1490) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 345.174124] init: tty3 main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 345.174388] init: tty6 main process (1498) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 345.174425] init: tty6 main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 345.174684] init: acpid main process (1531) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 345.174722] init: acpid main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 345.174957] init: cron main process (1533) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 345.174994] init: cron main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 345.175229] init: atd main process (1535) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 345.175267] init: atd main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 345.175506] init: tty1 main process (1714) killed by KILL signal Aug 8 20:01:58 DellE520 kernel: [ 345.175543] init: tty1 main process ended, respawning Aug 8 20:01:58 DellE520 kernel: [ 351.147484] audit_printk_skb: 11 callbacks suppressed Aug 8 20:01:58 DellE520 kernel: [ 351.147490] type=1400 audit(1375956118.934:25): apparmor="STATUS" operation="profile_replace" name="/usr/lib/cups/backend/cups-pdf" pid=25583 comm="apparmor_parser" Aug 8 20:01:58 DellE520 kernel: [ 351.148292] type=1400 audit(1375956118.938:26): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/cupsd" pid=25583 comm="apparmor_parser" Aug 8 20:01:59 DellE520 udev-configure-printer: add /module/lp Aug 8 20:01:59 DellE520 udev-configure-printer: Failed to get parent Aug 8 20:01:59 DellE520 kernel: [ 351.695619] init: plymouth-upstart-bridge main process (25601) terminated with status 1 Aug 8 20:02:00 DellE520 dbus[25594]: [system] Activating service name='org.freedesktop.ColorManager' (using servicehelper) Aug 8 20:02:00 DellE520 acpid: client connected from 25608[0:0] Aug 8 20:02:00 DellE520 acpid: 1 client rule loaded Aug 8 20:02:01 DellE520 dbus[25594]: [system] Successfully activated service 'org.freedesktop.ColorManager' Aug 8 20:02:32 DellE520 dbus[25594]: [system] Failed to activate service 'org.freedesktop.Avahi': timed out Aug 8 20:02:38 DellE520 dbus[25594]: [system] Activating service name='org.freedesktop.ConsoleKit' (using servicehelper) Aug 8 20:02:38 DellE520 dbus[25594]: [system] Activating service name='org.freedesktop.PolicyKit1' (using servicehelper) Aug 8 20:02:38 DellE520 polkitd[25824]: started daemon version 0.104 using authority implementation `local' version `0.104' Aug 8 20:02:38 DellE520 dbus[25594]: [system] Successfully activated service 'org.freedesktop.PolicyKit1' Aug 8 20:02:38 DellE520 dbus[25594]: [system] Successfully activated service 'org.freedesktop.ConsoleKit' You wanted me to check BIOS version. I did this after having rebooted (with non-PAE kernel) after that OOM crash: psz@DellE520:~$ sudo dmidecode -s bios-version && sudo dmidecode -s bios-release-date 2.4.0 05/24/2007 psz@DellE520:~$ Hope this helps. Cheers, Paul Paul Szabo