Messages in this thread | | | Subject | backing up ext4 fs, system unresponsive, thrashing like crazy even though swap is unused | From | Dimitrios Apostolou <> | Date | Sun, 25 Nov 2012 17:03:35 +0200 |
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Hello list,
on an old PIII-500MHz laptop, 128MB RAM, kernel 3.6.6, I started a backup process (tar|xz -4, nice'd and ionice'd -c3) from ext4 on local ATA disk to ext3 on external USB disk (USB-2.0 port on PCMCIA card). Even though earlier system load was minimal, free memory was plenty, the system now is unresponsive and is thrashing the disk, but the swapfile is rarely touched.
I managed to get some information by renicing a root console to -20, but even then each keypress showed with a minimum 10s delay! In the attached file you can see the dmesg output, SysRq+{W,T}, ps, vmstat, slabs, meminfo.
I think I'm seeing paging of executable pages because ext4_inode_cache is aggressively using all memory, evicting other pages. However under no condition should realtime processes be unresponsive. What do you think? Please note that I've set vm.swappiness to 0 and gradually increased vm.vfs_cache_pressure to 1000000, but see no difference.
Thanks in advance, Dimitris
P.S. Please CC me in all replies
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