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Generators
----------
Problem
=======
Until 0.5.2 Pyroute2 collected all the responses in a list
and returned them at once. It may be ok as long as there is
not so many objects to return. But let's say there are some
thousands of routes::
$ ip ro | wc -l
315417
Now we use a script to retrieve the routes::
import sys
from pyroute2 import config
from pyroute2 import IPRoute
config.nlm_generator = (sys.argv[1].lower()
if len(sys.argv) > 1
else 'false') == 'true'
with IPRoute() as ipr:
for route in ipr.get_routes():
pass
If the library collects all the routes in a list and returns
the list, it may take a lot of memory::
$ /usr/bin/time -v python e.py false
Command being timed: "python e.py false"
User time (seconds): 30.42
System time (seconds): 3.63
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:34.09
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 2416472
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 604787
Voluntary context switches: 9
Involuntary context switches: 688
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
2416472 kbytes of RSS. Pretty much.
Solution
========
Now we use generator to iterate the results::
$ /usr/bin/time -v python e.py true
Command being timed: "python e.py true"
User time (seconds): 18.48
System time (seconds): 0.99
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:19.49
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 45132
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 433589
Voluntary context switches: 9
Involuntary context switches: 244
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
45132 kbytes of RSS. That's the difference. Say we have a bit more
routes::
$ ip ro | wc -l
678148
Without generators the script will simply run ot of memory. But with
the generators::
$ /usr/bin/time -v python e.py true
Command being timed: "python e.py true"
User time (seconds): 39.63
System time (seconds): 2.78
Percent of CPU this job got: 99%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:42.75
Average shared text size (kbytes): 0
Average unshared data size (kbytes): 0
Average stack size (kbytes): 0
Average total size (kbytes): 0
Maximum resident set size (kbytes): 45324
Average resident set size (kbytes): 0
Major (requiring I/O) page faults: 0
Minor (reclaiming a frame) page faults: 925560
Voluntary context switches: 11
Involuntary context switches: 121182
Swaps: 0
File system inputs: 0
File system outputs: 0
Socket messages sent: 0
Socket messages received: 0
Signals delivered: 0
Page size (bytes): 4096
Exit status: 0
Again, 45324 kbytes of RSS.
Configuration
=============
To turn the generator option on, one should set ``pyroute2.config.nlm_generator``
to ``True``. By default is ``False`` not to break existing projects.::
from pyroute2 import config
from pyroute2 import IPRoute
config.nlm_generator = True
with IPRoute() as ipr:
for route in ipr.get_routes():
handle(route)
IPRoute and generators
======================
IPRoute objects will return generators only for methods that employ ``GET_...``
requests like ``get_routes()``, ``get_links()``, ``link('dump', ...)``, ``addr('dump', ...)``.
Setters will work as usually to apply changes immediately.
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