Date: Fri, 5 Feb 2010 17:45:01 -0500 From: Linda Messerschmidt <linda.messerschmidt@gmail.com> To: Dan Nelson <dnelson@allantgroup.com> Cc: freebsd-hackers@freebsd.org Subject: Re: ps "time" field jumps backward Message-ID: <237c27101002051445m3392115bhf8ed2ae61d56e0fa@mail.gmail.com> In-Reply-To: <20100205212837.GA43582@dan.emsphone.com> References: <237c27101002050857r78003779mb41eae44f850829b@mail.gmail.com> <20100205212837.GA43582@dan.emsphone.com>
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On Fri, Feb 5, 2010 at 4:28 PM, Dan Nelson <dnelson@allantgroup.com> wrote: > Ideally, top and ps would total up all > the per-thread CPU counts when displaying the per-process numbers, but it > doesn't seem to. It does seem to total them: $ ps axHo pid,lwp,time,wchan,comm | awk '$1 == 1647' 1647 100401 0:00.63 select mysqld 1647 100466 0:11.08 sigwai mysqld 1647 100521 0:00.00 ucond mysqld $ ps axo pid,lwp,time,wchan,comm | awk '$1 == 1647' 1647 100521 0:11.71 ucond mysqld But you put me on the right track. I ran both side by side for awhile, and found that ps/top only sums up those threads that haven't already exited. I.e., once a thread has exited, it's as if its usage never happened from the perspective of ps and top's total calculation. That seems like undesirable behavior, particularly if it conceals CPU-churning behavior by short-lived threads, but possibly very hard to change. :( I wonder if the system accounting records are more accurate? Thanks for pointing me in the right direction!
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