many processes stuck in "hmrrcm", system unusable

Simon 'corecode' Schubert corecode at fs.ei.tum.de
Sun Oct 4 10:00:55 PDT 2009


Matthew Dillon wrote:
:
:On chlamydia I have many processes stuck in "hmrrcm", making the system 
:unusable - can't open new shells, etc.  After a minute or two the 
:situation seems to improve again.

    This is an inode moderation mechanic which will typically occur if
    large numbers (thousands) of inodes have been dirtied and need to
    be updated on-media.  It prevents hammer's inode structure allocations
    from blowing away kernel memory and crashing the system.
    A rm -rf or a tar extract is the most typical culprit but atime
    updates can create issues as well if large portions of the filesystem
    are being randomly read.  You can try mounting noatime to address
    atime issues.
Shouldn't we rather try to fix the issue, i.e. make hammer work just a 
little bit performant and capable of concurrent use?  I think now that 
the code is stable we should start investigating performance (latency) 
issues and address them.

cheers
  simon
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