[ovirt-devel] [VDSM][JSON] jsonrpc coding/encoding performance on RHEL/Centos 6
Nir Soffer
nsoffer at redhat.com
Mon Nov 10 12:21:53 UTC 2014
----- Original Message -----
> From: "Francesco Romani" <fromani at redhat.com>
> To: devel at ovirt.org
> Sent: Monday, November 10, 2014 10:02:44 AM
> Subject: [ovirt-devel] [VDSM][JSON] jsonrpc coding/encoding performance on RHEL/Centos 6
>
> Hi everyone,
>
> I was doing JSON-RPC investigation recently, running VDSM on RHEL6.{5,6},
> and while some initial profile work, I discovered a (little) performance
> degradation
> about pure JSONRPC coding/encoding, *only* on the above platforms. Here's
> why:
>
> - the JSON codec module in the python stdlib is based on simplejson
> - (thus) simplejson API is identical to stdlib's json module API
> - python 2.6 JSON codec is (based on) simplejson 1.9
> - python 2.7 JSON codec is (based on) simplejson 2.0.9, with significant
> speedups. See
> https://docs.python.org/2/whatsnew/2.7.html#new-and-improved-modules and
> https://bugs.python.org/issue4136
> - RHEL6.x/Centos 6.x includes python 2.6, so here (and only here) JSON codec
> is unnecessarily slower.
> - RHEL6.x (surely) and CentOS 6.x (need to check, don't see why not) includes
> anyway simplejson 2.0.9 as external package
>
> So, it seems to me that we can get python 2.7 speed even on stable platform
> with
> a five line patch:
>
> === cut here ===
> diff --git a/lib/yajsonrpc/__init__.py b/lib/yajsonrpc/__init__.py
> index b3fd590..6682fc3 100644
> --- a/lib/yajsonrpc/__init__.py
> +++ b/lib/yajsonrpc/__init__.py
> @@ -12,7 +12,10 @@
> # You should have received a copy of the GNU General Public
> # License along with this program; if not, write to the Free Software
> # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
> -import json
> +try:
> + import simplejson as json
> +except ImportError
> + import json
> import logging
> from functools import partial
> from Queue import Queue
> === cut here ===
We have vdsm/lib/compat.py for this stuff.
Then everyone needing json will do "from vdsm.compat import json"
>
> Here's an excerpt of the effects of this patch, using an initial still rough
> bencmark
> - once again 100 VMs boot, is the beginning of every testing routine from
> mine,
> so nothing new here.
>
> Let's consider two initial profiles. Please note that
> 1) the amount of calls is not the same (error from mine in profiling, need
> more precise bench)
> but still
> 2) using 2.0.9 module JSON just vanishes from the profile alltogether
>
> Vanilla VDSM, stdlib json, top 20 expensive calls
>
> ncalls tottime percall cumtime percall filename:lineno(function)
> 19/100 127.216 6.696 9.974 0.100
> /usr/lib/python2.6/site-packages/mom/GuestMonitor.py:51(GuestMonitor.run)
> 1555/1635 41.180 0.026 58.566 0.036
> /usr/lib64/python2.6/threading.py:481(Thread.run)
> 11708/1553160 11.967 0.001 37.921 0.000
> /usr/lib64/python2.6/copy.py:144(deepcopy)
> 1268613 6.154 0.000 9.209 0.000
> /usr/lib64/python2.6/copy.py:261(_keep_alive)
> 4890/130093 6.149 0.001 37.596 0.000
> /usr/lib64/python2.6/copy.py:251(_deepcopy_dict)
> 497858/2070078 5.224 0.000 11.102 0.000
> /usr/lib64/python2.6/json/encoder.py:284(JSONEncoder._iterencode)
> 498440/1333474 4.187 0.000 10.368 0.000
> /usr/lib64/python2.6/json/encoder.py:213(JSONEncoder._iterencode_dict)
> 12/100 4.115 0.343 4.130 0.041
> /usr/share/vdsm/virt/sampling.py:424(VmStatsThread.run)
> 43826 3.692 0.000 6.516 0.000
> /usr/lib64/python2.6/xml/dom/expatbuilder.py:743(ExpatBuilderNS.start_element_handler)
> 7345 3.657 0.000 11.047 0.002
> /usr/share/vdsm/virt/vm.py:2264(Vm._getRunningVmStats)
> 9666/320508 3.568 0.000 3.572 0.000
> /usr/lib64/python2.6/xml/dom/minidom.py:305(_get_elements_by_tagName_helper)
> 274994/275000 3.339 0.000 5.593 0.000
> /usr/lib64/python2.6/StringIO.py:208(StringIO.write)
> 90217 1.823 0.000 1.870 0.000
> /usr/lib64/python2.6/xml/dom/minidom.py:349(Attr.__init__)
> 44025/44036 1.666 0.000 2.470 0.000
> /usr/share/vdsm/storage/lvm.py:217(makeLV)
> 144212/144226 1.287 0.000 1.292 0.000
> /usr/lib/python2.6/site-packages/vdsm/utils.py:285(convertToStr)
> 201 1.285 0.006 7.278 0.036
> /usr/share/vdsm/storage/lvm.py:411(LVMCache._reloadlvs)
> 109880 1.235 0.000 1.283 0.000
> /usr/lib64/python2.6/xml/dom/minidom.py:281(Document._append_child)
> 57874 1.163 0.000 1.799 0.000
> /usr/lib64/python2.6/xml/dom/expatbuilder.py:274(ExpatBuilderNS.character_data_handler_cdata)
> 1130859 1.160 0.000 1.160 0.000
> /usr/lib64/python2.6/copy.py:197(_deepcopy_atomic)
> 3021/3022 1.121 0.000 2.554 0.001
> /usr/lib64/python2.6/inspect.py:247(getmembers)
>
>
> patch applied, top 20 expensive calls
>
> 24/100 117.222 4.884 13.372 0.134
> /usr/lib/python2.6/site-packages/mom/GuestMonitor.py:51(GuestMonitor.run)
> 1209/1302 60.812 0.050 64.963 0.050
> /usr/lib64/python2.6/threading.py:481(Thread.run)
> 9243/1235834 10.259 0.001 33.047 0.000
> /usr/lib64/python2.6/copy.py:144(deepcopy)
> 13/100 7.007 0.539 7.281 0.073
> /usr/share/vdsm/virt/sampling.py:424(VmStatsThread.run)
> 4116/103669 5.536 0.001 32.779 0.000
> /usr/lib64/python2.6/copy.py:251(_deepcopy_dict)
> 9670/320560 4.437 0.000 4.443 0.000
> /usr/lib64/python2.6/xml/dom/minidom.py:305(_get_elements_by_tagName_helper)
> 5653 3.232 0.001 9.443 0.002
> /usr/share/vdsm/virt/vm.py:2264(Vm._getRunningVmStats)
> 43836 3.117 0.000 7.304 0.000
> /usr/lib64/python2.6/xml/dom/expatbuilder.py:743(ExpatBuilderNS.start_element_handler)
> 274967/275000 2.955 0.000 6.833 0.000
> /usr/lib64/python2.6/StringIO.py:208(StringIO.write)
> 1100/28500 2.376 0.002 12.881 0.000
> /usr/share/vdsm/virt/vmxml.py:489(Element.__hacked_writexml)
> 43745/44036 1.729 0.000 2.736 0.000
> /usr/share/vdsm/storage/lvm.py:217(makeLV)
> 90217/90221 1.695 0.000 1.953 0.000
> /usr/lib64/python2.6/xml/dom/minidom.py:349(Attr.__init__)
> 201 1.549 0.008 7.725 0.038
> /usr/share/vdsm/storage/lvm.py:411(LVMCache._reloadlvs)
> 57888 1.441 0.000 2.216 0.000
> /usr/lib64/python2.6/xml/dom/expatbuilder.py:274(ExpatBuilderNS.character_data_handler_cdata)
> 2351/2354 1.262 0.001 2.750 0.001
> /usr/lib64/python2.6/inspect.py:247(getmembers)
> 992794 1.232 0.000 8.027 0.000
> /usr/lib64/python2.6/copy.py:261(_keep_alive)
> 4827 1.150 0.000 1.368 0.000
> /usr/lib/python2.6/site-packages/mom/Policy/spark.py:211(Parser.buildState)
> 108040 1.119 0.000 1.119 0.000
> /usr/lib/python2.6/site-packages/vdsm/utils.py:285(convertToStr)
> 336771/422122 1.106 0.000 2.575 0.000
> /usr/share/vdsm/protocoldetector.py:108(MultiProtocolAcceptor._process_events)
> 883021 0.987 0.000 0.987 0.000
> /usr/lib64/python2.6/copy.py:197(_deepcopy_atomic)
>
>
> Indeed this is a microbenchmark, but my point is we *recover* some speed at
> nearly
> zero cost and risk.
>
> Now, the question is:
> Do we want this patch? Do we want it on master? On 3.5 branch? Only on
> RHEL/Centos 6 platforms?
Nice catch - using pure python encoder/decoder is indeed much slower, strange
that Python 2.6 does not include the c extension.
I think we would like to use simplejson on all platforms, to make the build
and support simpler.
Nir
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