slab/kernel memory problem

From: Alexander Lazarevich (alazarev_at_itg.uiuc.edu)
Date: 09/29/05

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    Date: Thu, 29 Sep 2005 11:23:26 -0500 (CDT)
To: General Red Hat Linux discussion list <redhat-list@redhat.com>

    We have a RHEL4-AS 64bit system, and a FC364bit system. Both running most
    recent kernels.

    We've got bad memory problems. The kernel is sucking up quite a bit of
    memory, check out Slab in meminfo:

    [root@hostname ~]# cat /proc/meminfo
    MemTotal: 8078596 kB
    MemFree: 486480 kB
    Buffers: 1075532 kB
    Cached: 527284 kB
    SwapCached: 1384 kB
    Active: 2120352 kB
    Inactive: 1019628 kB
    HighTotal: 0 kB
    HighFree: 0 kB
    LowTotal: 8078596 kB
    LowFree: 486480 kB
    SwapTotal: 2096472 kB
    SwapFree: 2053372 kB
    Dirty: 28 kB
    Writeback: 0 kB
    Mapped: 1564776 kB
    Slab: 4424180 kB
    CommitLimit: 6135768 kB
    Committed_AS: 1836712 kB
    PageTables: 9952 kB
    VmallocTotal: 34359738367 kB
    VmallocUsed: 1356 kB
    VmallocChunk: 34359736951 kB
    HugePages_Total: 0
    HugePages_Free: 0
    Hugepagesize: 2048 kB

    Then, slabtop is showing what is using all that slab mem:

      Active / Total Objects (% used) : 9028210 / 9033666 (99.9%)
      Active / Total Slabs (% used) : 1105829 / 1105834 (100.0%)
      Active / Total Caches (% used) : 94 / 135 (69.6%)
      Active / Total Size (% used) : 108142.02K / 108819.82K (99.4%)
      Minimum / Average / Maximum Object : 0.02K / 0.01K / 128.00K

       OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
    4181455 4181452 99% 0.78K 836291 5 3345164K ext3_inode_cache
    4129011 4129007 99% 0.23K 242883 17 971532K dentry_cache

    Why in the heck is the system trying to use all this memory to cache
    ext3 inodes? This happens on both FC364bit and RHEL4-AS64bit.

    I've search google and bugzilla, couldn't find anything.

    Anyone see this as well?

    Thanks!

    Alex 

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