[Click] Core performance checkins
Beyers Cronje
bcronje at gmail.com
Thu Feb 10 09:28:45 EST 2011
Hi Eddie,
I've reverted to the pre-coreperformance code on the "semi-production"
server for now, and will see if I can replicate the issue on my dev server.
Hopefully I can use Cliff's test case to replicate and troubleshoot. Will
keep you posted. In all honesty though I haven't wrapped my head around
memory barriers and the like, so I'm not sure how far I will get on my own
:(
Cliff, care to host an online advanced multithreading course ? :)
Beyers
On Thu, Feb 10, 2011 at 4:15 PM, Eddie Kohler <kohler at cs.ucla.edu> wrote:
> I'm very sorry about this regression... Unfortunately due to travel it's
> going to hard to look at this until the weekend. I would rather not yet
> revert coreperformance. Can you handle this situation?
>
> Eddie
>
>
>
> On 02/09/2011 05:22 AM, Beyers Cronje wrote:
>
>> Hi Eddie,
>>
>> Some info that I'm sure will help debugging. I configured click
>> with --enable-schedule-debugging=extra and also enabled
>> NOTIFIERQUEUE_DEBUG
>>
>> It seems Unqueue gets stuck in the pending list. See the output below:
>>
>> read q.length
>> 1000
>>
>> read q.notifier_state
>> notifier on
>> task 0x19387b0 [uq :: Unqueue] scheduled
>>
>> read uq.scheduled
>> true /* but pending */
>>
>> read uq.notifier
>> empty.0/1:1*
>>
>>
>> Unqueue stays in this scheduled but pending state for an undetermined
>> period
>> of time, up to minutes some times.
>>
>> Any idea where I can start on fixing this bug?
>>
>> Beyers
>>
>>
>> On Wed, Feb 9, 2011 at 2:52 AM, Beyers Cronje <bcronje at gmail.com
>> <mailto:bcronje at gmail.com>> wrote:
>>
>> Update - Strange, after typing my previous email I checked again, and
>> all
>> of a sudden Unqueue was pulling packets again. Not sure if me breaking
>> into Click with gdb kick-started, it again :) or if it's a intermittent
>> issue.
>>
>>
>> On Wed, Feb 9, 2011 at 2:41 AM, Beyers Cronje <bcronje at gmail.com
>> <mailto:bcronje at gmail.com>> wrote:
>>
>> Hi Eddie,
>>
>> Since running this merge I've been experiencing issues with
>> usermode
>> multithreading. I'm using commit
>> 9419098acbdc20837e37f3033c40661809431f8d
>> I do believe the issues are related to the changes of this merged,
>> as
>> I was running the same config on pre-coreperformance merge code
>> without any issues.
>>
>> *Simplified Config used:*
>>
>> fd::FromDAG(/dev/dag0) -> cl1::Classifier(12/0800) ->
>> MarkIPHeader(14)
>> -> ipc1::IPClassifier(udp port 1646);
>> sfp::SFP();
>> q::ThreadSafeQueue;
>> log::Logger(sfp, 1800);
>>
>> ipc1 -> RadAccounting -> q;
>> q -> uq::Unqueue -> aupcc::Counter -> sfp;
>>
>> StaticThreadSched(fd 0, uq 1, log 2);
>>
>> *Problem Description:*
>> The 3 threads in the config: FromDAG and Unqueue do what their
>> names
>> indicate, and Logger has a timer that schedules its task once every
>> 30min. Everything runs fine initially and then somewhere along the
>> line Unqueue stops pulling packets from the queue which leads to a
>> constant queue overflow. When this happens I can see FromDAG is
>> still
>> working as q.drops increases constantly, and Logger also fires away
>> every 30min. Note push rate from FromDAG is quite high, but
>> what RadAccounting pushes into queue is very low ~ 100pps, which
>> means
>> queue is most of the time empty and Unqueue is not scheduled.
>>
>> Unfortunately I didn't configure debug scheduling, which would've
>> helped. I did notice Unqueue.scheduled always returned true, even
>> though it never actually ran. Not sure if the following will help,
>> gdb
>> shows the following:
>>
>> (gdb) info threads
>> 3 Thread 0x7fa422559700 (LWP 27205) 0x000000392cedb0b3 in poll
>> ()
>> from /lib64/libc.so.6
>> 2 Thread 0x7fa421d58700 (LWP 27206) 0x000000392cedcee3 in
>> select
>> () from /lib64/libc.so.6
>> * 1 Thread 0x7fa432cfb740 (LWP 27197) FromDAG::process_packet
>> (this=0x1afc570, erf_record=0x7fa423258bf0, rlen=<value optimized
>> out>) at ../elements/local/fromdag.cc:193
>> (gdb) thread 2
>> [Switching to thread 2 (Thread 0x7fa421d58700 (LWP 27206))]#0
>> 0x000000392cedb0b3 in poll () from /lib64/libc.so.6
>> (gdb) bt
>> #0 0x000000392cedb0b3 in poll () from /lib64/libc.so.6
>> #1 0x000000000058bc36 in Master::run_selects_poll (this=0x1afacc0,
>> thread=0x1afb8b0, more_tasks=false) at ../lib/master.cc:862
>> #2 0x000000000058c4ec in Master::run_selects (this=0x1afacc0,
>> thread=0x1afb8b0) at ../lib/master.cc:1050
>> #3 0x000000000057ddf1 in run_os (this=0x1afb8b0) at
>> ../lib/routerthread.cc:447
>> #4 RouterThread::driver (this=0x1afb8b0) at
>> ../lib/routerthread.cc:568
>> #5 0x0000000000556dc9 in thread_driver (user_data=<value optimized
>> out>) at click.cc:414
>> #6 0x000000392d206d5b in start_thread () from
>> /lib64/libpthread.so.0
>> #7 0x000000392cee4aad in clone () from /lib64/libc.so.6
>> (gdb) thread 3
>> [Switching to thread 3 (Thread 0x7fa422559700 (LWP 27205))]#0
>> 0x000000392cedcee3 in select () from /lib64/libc.so.6
>> (gdb) bt
>> #0 0x000000392cedcee3 in select () from /lib64/libc.so.6
>> #1 0x000000000058c4bf in Master::run_selects (this=0x1afacc0,
>> thread=0x1afb7e0) at ../lib/master.cc:1015
>> #2 0x000000000057ddf1 in run_os (this=0x1afb7e0) at
>> ../lib/routerthread.cc:447
>> #3 RouterThread::driver (this=0x1afb7e0) at
>> ../lib/routerthread.cc:568
>> #4 0x0000000000556dc9 in thread_driver (user_data=<value optimized
>> out>) at click.cc:414
>> #5 0x000000392d206d5b in start_thread () from
>> /lib64/libpthread.so.0
>> #6 0x000000392cee4aad in clone () from /lib64/libc.so.6
>> (gdb) thread 1
>> [Switching to thread 1 (Thread 0x7fa432cfb740 (LWP 27197))]#0
>> 0x000000392d20ebfd in nanosleep () from /lib64/libpthread.so.0
>> (gdb) bt
>> #0 FromDAG::process_packet (this=0x1afc570,
>> erf_record=0x7fa423258bf0, rlen=<value optimized out>) at
>> ../elements/local/fromdag.cc:193
>> #1 0x00000000004d6402 in FromDAG::run_task (this=0x1afc570) at
>> ../elements/local/fromdag.cc:150
>> #2 0x000000000057dbe6 in fire (this=0x1afb710) at
>> ../include/click/task.hh:612
>> #3 run_tasks (this=0x1afb710) at ../lib/routerthread.cc:410
>> #4 RouterThread::driver (this=0x1afb710) at
>> ../lib/routerthread.cc:600
>> #5 0x0000000000558513 in main (argc=<value optimized out>,
>> argv=<value optimized out>) at click.cc:639
>>
>> One thing to note, for various reasons I'm doing something very
>> unclick-like with FromDAG where I allow it to block up to 10ms. For
>> my
>> specific requirements this is not a problem, but just in case it
>> might
>> affect the way the new task handling operates it's worth noting.
>>
>> Beyers
>>
>> On Sun, Feb 6, 2011 at 1:23 AM, Eddie Kohler <kohler at cs.ucla.edu
>> <mailto:kohler at cs.ucla.edu>> wrote:
>>
>> Hi all,
>>
>> This is just a note to say that I've merged the
>> "coreperformance"
>> branch
>> with master. There are several changes that may speed up
>> particularly
>> simple configurations, and that (more importantly) may make it
>> easier to
>> experiment with different multithreading setups. (For instance
>> I
>> believe switching a task from one thread to another is faster
>> now.) Let
>> me know if you experience any problems
>>
>> Eddie
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>>
>>
>>
>>
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