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https://issues.apache.org/jira/browse/CASSANDRA-9673?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14629357#comment-14629357
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Stefania commented on CASSANDRA-9673:
-------------------------------------
I've attached an archive containing .jfr files for trunk and the patched
branch. I generated the files using the following dtest:
{code}
def logged_batch_stress_test(self):
"""
@jira_ticket CASSANDRA-9673, a stress test to record any improvements
in GC usage
"""
cluster = self.cluster
cluster.populate(3)
cluster.start(wait_other_notice=True,
jvm_args=["-XX:+UnlockCommercialFeatures", "-XX:+FlightRecorder"])
nodes = cluster.nodelist()
self._start_jfr_recording(nodes)
nodes[0].stress(['user', 'profile=/home/stefania/git/cstar/9673.yaml',
'ops(insert=1,)', 'n=50000', '-rate', 'threads=8'])
self._dump_jfr_recording(nodes)
def _start_jfr_recording(self, nodes):
"""
Start jfr recording provided the cluster was started with
jvm_args=["-XX:+UnlockCommercialFeatures", "-XX:+FlightRecorder"]
"""
for node in nodes:
p = subprocess.Popen(['jcmd', str(node.pid), 'JFR.start'],
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
stdout, stderr = p.communicate()
debug(stdout)
debug(stderr)
def _dump_jfr_recording(self, nodes):
"""
Save jfr recording to file
"""
for node in nodes:
p = subprocess.Popen(['jcmd', str(node.pid), 'JFR.dump',
'recording=1', 'filename=recording_{}.jfr'.format(node.address())],
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
stdout, stderr = p.communicate()
debug(stdout)
debug(stderr)
{code}
9673.yaml is included in the archive attached or available
[here|https://dl.dropboxusercontent.com/u/15683245/9673.yaml]. I couldn't
figure out any other way to use logged batches in cassandra-stress other than
with a user schema, that is the only reason for the user schema.
I've also run a cperf test with the same stress test:
http://cstar.datastax.com/tests/id/20a0d848-2b84-11e5-be06-42010af0688f
I don't notice any differences in the cperf test and I am not at all familiar
with analyzing .jfr files (first time I use FlightRecorder ever). If anything
it seems to me the patched branch uses less memory but has more GCs but perhaps
I should have used a bigger sample. I also only looked at the coordinator .jfrs
(the first node).
[~JoshuaMcKenzie], any suggestions or comments?
> Improve batchlog write path
> ---------------------------
>
> Key: CASSANDRA-9673
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9673
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Aleksey Yeschenko
> Assignee: Stefania
> Fix For: 3.0.0 rc1
>
> Attachments: 9673.tar.gz
>
>
> Currently we allocate an on-heap {{ByteBuffer}} to serialize the batched
> mutations into, before sending it to a distant node, generating unnecessary
> garbage (potentially a lot of it).
> With materialized views using the batchlog, it would be nice to optimise the
> write path:
> - introduce a new verb ({{Batch}})
> - introduce a new message ({{BatchMessage}}) that would encapsulate the
> mutations, expiration, and creation time (similar to {{HintMessage}} in
> CASSANDRA-6230)
> - have MS serialize it directly instead of relying on an intermediate buffer
> To avoid merely shifting the temp buffer to the receiving side(s) we should
> change the structure of the batchlog table to use a list or a map of
> individual mutations.
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