• Shailabh Nagar's avatar
    [PATCH] delay accounting taskstats interface send tgid once · ad4ecbcb
    Shailabh Nagar authored
    Send per-tgid data only once during exit of a thread group instead of once
    with each member thread exit.
    Currently, when a thread exits, besides its per-tid data, the per-tgid data
    of its thread group is also sent out, if its thread group is non-empty.
    The per-tgid data sent consists of the sum of per-tid stats for all
    *remaining* threads of the thread group.
    This patch modifies this sending in two ways:
    - the per-tgid data is sent only when the last thread of a thread group
      exits.  This cuts down heavily on the overhead of sending/receiving
      per-tgid data, especially when other exploiters of the taskstats
      interface aren't interested in per-tgid stats
    - the semantics of the per-tgid data sent are changed.  Instead of being
      the sum of per-tid data for remaining threads, the value now sent is the
      true total accumalated statistics for all threads that are/were part of
      the thread group.
    The patch also addresses a minor issue where failure of one accounting
    subsystem to fill in the taskstats structure was causing the send of
    taskstats to not be sent at all.
    The patch has been tested for stability and run cerberus for over 4 hours
    on an SMP.
    [akpm@osdl.org: bugfixes]
    Signed-off-by: default avatarShailabh Nagar <nagar@watson.ibm.com>
    Signed-off-by: default avatarBalbir Singh <balbir@in.ibm.com>
    Cc: Jay Lan <jlan@engr.sgi.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
fork.c 40.6 KB