Re: [lttng-dev] High memory consumption issue on RCU side
On Sat, Sep 24, 2016 at 03:34:47PM +, Mathieu Desnoyers wrote: > - On Sep 24, 2016, at 11:22 AM, Paul E. McKenney > paul...@linux.vnet.ibm.com wrote: > > > On Sat, Sep 24, 2016 at 10:42:24AM +0300, Evgeniy Ivanov wrote: > >> Hi Mathieu, > >> > >> On Sat, Sep 24, 2016 at 12:59 AM, Mathieu Desnoyers > >>wrote: > >> > - On Sep 22, 2016, at 3:14 PM, Evgeniy Ivanov lolkaanti...@gmail.com > >> > wrote: > >> > > >> >> Hi all, > >> >> > >> >> I'm investigating high memory usage of my program: RSS varies between > >> >> executions in range 20-50 GB, though it should be determenistic. I've > >> >> found that all the memory is allocated in this stack: > >> >> > >> >> Allocated 17673781248 bytes in 556 allocations > >> >>cds_lfht_alloc_bucket_table3 from liburcu-cds.so.2.0.0 > >> >>_do_cds_lfht_resize from liburcu-cds.so.2.0.0 > >> >>do_resize_cb from liburcu-cds.so.2.0.0 > >> >>call_rcu_thread from liburcu-qsbr.so.2.0.0 > >> >>start_thread from libpthread-2.12.so > >> >>clonefrom libc-2.12.so > >> >> > >> >> According pstack it should be quiescent state. Call thread waits on > >> >> syscall: > >> >> syscall > >> >> call_rcu_thread > >> >> start_thread > >> >> clone > >> >> > >> >> We use urcu-0.8.7, only rculfhash (QSBR). Is it some kind of leak in > >> >> RCU or any chance I misuse it? What would you recommend to > >> >> troubleshoot the situation? > >> > > >> > urcu-qsbr is the fastest flavor of urcu, but it is rather tricky to use > >> > well. > >> > Make sure that: > >> > > >> > - Each registered thread periodically reach a quiescent state, by: > >> > - Invoking rcu_quiescent_state periodically, and > >> > - Making sure to surround any blocking for relatively large amount of > >> > time by rcu_thread_offline()/rcu_thread_online(). > >> > > >> > In urcu-qsbr, the "default" state of threads is to be within a RCU > >> > read-side. > >> > Therefore, if you omit any of the two advice above, you end up in a > >> > situation > >> > where grace periods never complete, and therefore no call_rcu() > >> > callbacks can > >> > be processed. This effectively acts like a big memory leak. > >> > >> It was the original assumption, but in memory stacks I don't see such > >> allocations for my data. Instead huge allocations happen right in > >> call_rcu_thread. Memory footprint for my app is about 20 GB, erasing > >> RCU data is a rare operation, so almost 20 GB in rcu thread looks > >> suspecios. I'll try to not erase any RCU protected data and reproduce > >> the issue (complicated thing is that under memory tracer it happens > >> not so often). > > > > Interesting. Trying to figure out why your call_rcu_thread() would > > ever allocate memory. > > > > Ah! Do your RCU callbacks allocate memory? > > In this case yes: urculfhash allocates memory within a call rcu worker > thread when a hash table resize is performed. Is this then expected behavior? Though I must admit that 20GB sounds like some serious resizing... Thanx, Paul > Thanks, > > Mathieu > > > > > Thanx, Paul > > > >> > Hoping this helps, > >> > > >> > Thanks, > >> > > >> > Mathieu > >> > > >> > > >> > -- > >> > Mathieu Desnoyers > >> > EfficiOS Inc. > >> > http://www.efficios.com > >> > >> > >> > >> -- > >> Cheers, > >> Evgeniy > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com > ___ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
Re: [lttng-dev] High memory consumption issue on RCU side
All hash tables are created with 1024 initial buckets (no limit for max number of buckets). Only three tables can contain at most about 5 000 000 nodes, the rest (I think about 5000) tables contain at most 1000-5000 nodes. Big tables have UUID key and CityHash, small tables have a complicated binary key with SuperFastHash. Binary keys are the same between executions, but UUID are generated on the fly and if there're collisions it might explain why memory footprint varies so much. I've set both min and max buckets limits and now RSS looks constant between executions. Thank you very much for pointing to this! Do I understand it correctly, that besides load factor rculfhash also resizes depending on max number of nodes in any bucket? Is there any way to get number of buckets (sorry if I missed it looking into API) allocated by table? This would help to further troubleshoot the issue. On Sat, Sep 24, 2016 at 6:34 PM, Mathieu Desnoyerswrote: > - On Sep 24, 2016, at 11:22 AM, Paul E. McKenney > paul...@linux.vnet.ibm.com wrote: > >> On Sat, Sep 24, 2016 at 10:42:24AM +0300, Evgeniy Ivanov wrote: >>> Hi Mathieu, >>> >>> On Sat, Sep 24, 2016 at 12:59 AM, Mathieu Desnoyers >>> wrote: >>> > - On Sep 22, 2016, at 3:14 PM, Evgeniy Ivanov lolkaanti...@gmail.com >>> > wrote: >>> > >>> >> Hi all, >>> >> >>> >> I'm investigating high memory usage of my program: RSS varies between >>> >> executions in range 20-50 GB, though it should be determenistic. I've >>> >> found that all the memory is allocated in this stack: >>> >> >>> >> Allocated 17673781248 bytes in 556 allocations >>> >>cds_lfht_alloc_bucket_table3 from liburcu-cds.so.2.0.0 >>> >>_do_cds_lfht_resize from liburcu-cds.so.2.0.0 >>> >>do_resize_cb from liburcu-cds.so.2.0.0 >>> >>call_rcu_thread from liburcu-qsbr.so.2.0.0 >>> >>start_thread from libpthread-2.12.so >>> >>clonefrom libc-2.12.so >>> >> >>> >> According pstack it should be quiescent state. Call thread waits on >>> >> syscall: >>> >> syscall >>> >> call_rcu_thread >>> >> start_thread >>> >> clone >>> >> >>> >> We use urcu-0.8.7, only rculfhash (QSBR). Is it some kind of leak in >>> >> RCU or any chance I misuse it? What would you recommend to >>> >> troubleshoot the situation? >>> > >>> > urcu-qsbr is the fastest flavor of urcu, but it is rather tricky to use >>> > well. >>> > Make sure that: >>> > >>> > - Each registered thread periodically reach a quiescent state, by: >>> > - Invoking rcu_quiescent_state periodically, and >>> > - Making sure to surround any blocking for relatively large amount of >>> > time by rcu_thread_offline()/rcu_thread_online(). >>> > >>> > In urcu-qsbr, the "default" state of threads is to be within a RCU >>> > read-side. >>> > Therefore, if you omit any of the two advice above, you end up in a >>> > situation >>> > where grace periods never complete, and therefore no call_rcu() callbacks >>> > can >>> > be processed. This effectively acts like a big memory leak. >>> >>> It was the original assumption, but in memory stacks I don't see such >>> allocations for my data. Instead huge allocations happen right in >>> call_rcu_thread. Memory footprint for my app is about 20 GB, erasing >>> RCU data is a rare operation, so almost 20 GB in rcu thread looks >>> suspecios. I'll try to not erase any RCU protected data and reproduce >>> the issue (complicated thing is that under memory tracer it happens >>> not so often). >> >> Interesting. Trying to figure out why your call_rcu_thread() would >> ever allocate memory. >> >> Ah! Do your RCU callbacks allocate memory? > > In this case yes: urculfhash allocates memory within a call rcu worker > thread when a hash table resize is performed. > > Thanks, > > Mathieu > >> >> Thanx, Paul >> >>> > Hoping this helps, >>> > >>> > Thanks, >>> > >>> > Mathieu >>> > >>> > >>> > -- >>> > Mathieu Desnoyers >>> > EfficiOS Inc. >>> > http://www.efficios.com >>> >>> >>> >>> -- >>> Cheers, >>> Evgeniy > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com -- Cheers, Evgeniy ___ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
Re: [lttng-dev] High memory consumption issue on RCU side
On Sat, Sep 24, 2016 at 10:42:24AM +0300, Evgeniy Ivanov wrote: > Hi Mathieu, > > On Sat, Sep 24, 2016 at 12:59 AM, Mathieu Desnoyers >wrote: > > - On Sep 22, 2016, at 3:14 PM, Evgeniy Ivanov lolkaanti...@gmail.com > > wrote: > > > >> Hi all, > >> > >> I'm investigating high memory usage of my program: RSS varies between > >> executions in range 20-50 GB, though it should be determenistic. I've > >> found that all the memory is allocated in this stack: > >> > >> Allocated 17673781248 bytes in 556 allocations > >>cds_lfht_alloc_bucket_table3 from liburcu-cds.so.2.0.0 > >>_do_cds_lfht_resize from liburcu-cds.so.2.0.0 > >>do_resize_cb from liburcu-cds.so.2.0.0 > >>call_rcu_thread from liburcu-qsbr.so.2.0.0 > >>start_thread from libpthread-2.12.so > >>clonefrom libc-2.12.so > >> > >> According pstack it should be quiescent state. Call thread waits on > >> syscall: > >> syscall > >> call_rcu_thread > >> start_thread > >> clone > >> > >> We use urcu-0.8.7, only rculfhash (QSBR). Is it some kind of leak in > >> RCU or any chance I misuse it? What would you recommend to > >> troubleshoot the situation? > > > > urcu-qsbr is the fastest flavor of urcu, but it is rather tricky to use > > well. > > Make sure that: > > > > - Each registered thread periodically reach a quiescent state, by: > > - Invoking rcu_quiescent_state periodically, and > > - Making sure to surround any blocking for relatively large amount of > > time by rcu_thread_offline()/rcu_thread_online(). > > > > In urcu-qsbr, the "default" state of threads is to be within a RCU > > read-side. > > Therefore, if you omit any of the two advice above, you end up in a > > situation > > where grace periods never complete, and therefore no call_rcu() callbacks > > can > > be processed. This effectively acts like a big memory leak. > > It was the original assumption, but in memory stacks I don't see such > allocations for my data. Instead huge allocations happen right in > call_rcu_thread. Memory footprint for my app is about 20 GB, erasing > RCU data is a rare operation, so almost 20 GB in rcu thread looks > suspecios. I'll try to not erase any RCU protected data and reproduce > the issue (complicated thing is that under memory tracer it happens > not so often). Interesting. Trying to figure out why your call_rcu_thread() would ever allocate memory. Ah! Do your RCU callbacks allocate memory? Thanx, Paul > > Hoping this helps, > > > > Thanks, > > > > Mathieu > > > > > > -- > > Mathieu Desnoyers > > EfficiOS Inc. > > http://www.efficios.com > > > > -- > Cheers, > Evgeniy > ___ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
Re: [lttng-dev] High memory consumption issue on RCU side
- On Sep 24, 2016, at 11:22 AM, Paul E. McKenney paul...@linux.vnet.ibm.com wrote: > On Sat, Sep 24, 2016 at 10:42:24AM +0300, Evgeniy Ivanov wrote: >> Hi Mathieu, >> >> On Sat, Sep 24, 2016 at 12:59 AM, Mathieu Desnoyers >>wrote: >> > - On Sep 22, 2016, at 3:14 PM, Evgeniy Ivanov lolkaanti...@gmail.com >> > wrote: >> > >> >> Hi all, >> >> >> >> I'm investigating high memory usage of my program: RSS varies between >> >> executions in range 20-50 GB, though it should be determenistic. I've >> >> found that all the memory is allocated in this stack: >> >> >> >> Allocated 17673781248 bytes in 556 allocations >> >>cds_lfht_alloc_bucket_table3 from liburcu-cds.so.2.0.0 >> >>_do_cds_lfht_resize from liburcu-cds.so.2.0.0 >> >>do_resize_cb from liburcu-cds.so.2.0.0 >> >>call_rcu_thread from liburcu-qsbr.so.2.0.0 >> >>start_thread from libpthread-2.12.so >> >>clonefrom libc-2.12.so >> >> >> >> According pstack it should be quiescent state. Call thread waits on >> >> syscall: >> >> syscall >> >> call_rcu_thread >> >> start_thread >> >> clone >> >> >> >> We use urcu-0.8.7, only rculfhash (QSBR). Is it some kind of leak in >> >> RCU or any chance I misuse it? What would you recommend to >> >> troubleshoot the situation? >> > >> > urcu-qsbr is the fastest flavor of urcu, but it is rather tricky to use >> > well. >> > Make sure that: >> > >> > - Each registered thread periodically reach a quiescent state, by: >> > - Invoking rcu_quiescent_state periodically, and >> > - Making sure to surround any blocking for relatively large amount of >> > time by rcu_thread_offline()/rcu_thread_online(). >> > >> > In urcu-qsbr, the "default" state of threads is to be within a RCU >> > read-side. >> > Therefore, if you omit any of the two advice above, you end up in a >> > situation >> > where grace periods never complete, and therefore no call_rcu() callbacks >> > can >> > be processed. This effectively acts like a big memory leak. >> >> It was the original assumption, but in memory stacks I don't see such >> allocations for my data. Instead huge allocations happen right in >> call_rcu_thread. Memory footprint for my app is about 20 GB, erasing >> RCU data is a rare operation, so almost 20 GB in rcu thread looks >> suspecios. I'll try to not erase any RCU protected data and reproduce >> the issue (complicated thing is that under memory tracer it happens >> not so often). > > Interesting. Trying to figure out why your call_rcu_thread() would > ever allocate memory. > > Ah! Do your RCU callbacks allocate memory? In this case yes: urculfhash allocates memory within a call rcu worker thread when a hash table resize is performed. Thanks, Mathieu > > Thanx, Paul > >> > Hoping this helps, >> > >> > Thanks, >> > >> > Mathieu >> > >> > >> > -- >> > Mathieu Desnoyers >> > EfficiOS Inc. >> > http://www.efficios.com >> >> >> >> -- >> Cheers, >> Evgeniy -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com ___ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
Re: [lttng-dev] High memory consumption issue on RCU side
Hi Mathieu, On Sat, Sep 24, 2016 at 12:59 AM, Mathieu Desnoyerswrote: > - On Sep 22, 2016, at 3:14 PM, Evgeniy Ivanov lolkaanti...@gmail.com > wrote: > >> Hi all, >> >> I'm investigating high memory usage of my program: RSS varies between >> executions in range 20-50 GB, though it should be determenistic. I've >> found that all the memory is allocated in this stack: >> >> Allocated 17673781248 bytes in 556 allocations >>cds_lfht_alloc_bucket_table3 from liburcu-cds.so.2.0.0 >>_do_cds_lfht_resize from liburcu-cds.so.2.0.0 >>do_resize_cb from liburcu-cds.so.2.0.0 >>call_rcu_thread from liburcu-qsbr.so.2.0.0 >>start_thread from libpthread-2.12.so >>clonefrom libc-2.12.so >> >> According pstack it should be quiescent state. Call thread waits on syscall: >> syscall >> call_rcu_thread >> start_thread >> clone >> >> We use urcu-0.8.7, only rculfhash (QSBR). Is it some kind of leak in >> RCU or any chance I misuse it? What would you recommend to >> troubleshoot the situation? > > urcu-qsbr is the fastest flavor of urcu, but it is rather tricky to use well. > Make sure that: > > - Each registered thread periodically reach a quiescent state, by: > - Invoking rcu_quiescent_state periodically, and > - Making sure to surround any blocking for relatively large amount of > time by rcu_thread_offline()/rcu_thread_online(). > > In urcu-qsbr, the "default" state of threads is to be within a RCU read-side. > Therefore, if you omit any of the two advice above, you end up in a situation > where grace periods never complete, and therefore no call_rcu() callbacks can > be processed. This effectively acts like a big memory leak. It was the original assumption, but in memory stacks I don't see such allocations for my data. Instead huge allocations happen right in call_rcu_thread. Memory footprint for my app is about 20 GB, erasing RCU data is a rare operation, so almost 20 GB in rcu thread looks suspecios. I'll try to not erase any RCU protected data and reproduce the issue (complicated thing is that under memory tracer it happens not so often). > Hoping this helps, > > Thanks, > > Mathieu > > > -- > Mathieu Desnoyers > EfficiOS Inc. > http://www.efficios.com -- Cheers, Evgeniy ___ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev