Re: Memory Exclusion

From: Paul H. Hargrove (PHHargrove_at_lbl_dot_gov)
Date: Tue Nov 10 2009 - 14:02:50 PST

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    Currently BLCR will exclude :
    1) Pages mapped from a file and unmodified, which will include the code 
    and read-only data segments of the executable and shared libraries.  
    This may also included mmap()s performed by the application, if any.
    2) "Anonymous" (non file-backed) pages that are mapped in to the process 
    but not yet written to, which includes unused portions of the stack and 
    In the next release (target Jan 2010) we will have a mechanism that 
    allows applications and libraries to hint to BLCR about regions of 
    memory that can be excluded.  For instance, the OpenMPI developer that 
    works on checkpoint/restart has suggested that they might exclude any of 
    MPI's receive buffers that don't hold actual messages at the time the 
    checkpoint is taken.
    We are also working on incremental checkpointing for the next release.  
    In the case where one takes multiple checkpoints of the same process 
    over time, this will omit from a checkpoint any pages not written to 
    since the previous one.  However, when using this mechanism one needs 
    all the past checkpoints to restore (and so more disk space is required).
    Chris Chaudoir wrote:
    > To Paul et all,
    > I just started playing around with the latest version of BLCR (nice 
    > btw) and had a question...besides the expected methods of skipping the 
    > code and unused stack, can you describe the 'memory exclusion' methods 
    > in BLCR (or point me to the right documentation)?
    > Respectfully,
    >   Chris Chaudoir
    > BSEE & CS grad student
    Paul H. Hargrove                          PHHargrove_at_lbl_dot_gov
    Future Technologies Group                 Tel: +1-510-495-2352
    HPC Research Department                   Fax: +1-510-486-6900
    Lawrence Berkeley National Laboratory     

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