GitHub user witgo opened a pull request:
https://github.com/apache/spark/pull/15512
The SerializerInstance instance used when deserializing a TaskResult is not
reused
## What changes were proposed in this pull request?
The following code is called when the DirectTaskResult instance is
deserialized
```scala
def value(): T = {
if (valueObjectDeserialized) {
valueObject
} else {
// Each deserialization creates a new instance of SerializerInstance,
which is very time-consuming
val resultSer = SparkEnv.get.serializer.newInstance()
valueObject = resultSer.deserialize(valueBytes)
valueObjectDeserialized = true
valueObject
}
}
```
In the case of stage has a lot of tasks, reuse SerializerInstance instance
can improve the scheduling performance of three times
The test data is TPC-DS 2T (Parquet) and SQL statement as follows (query
2)):
```sql
select i_item_id,
avg(ss_quantity) agg1,
avg(ss_list_price) agg2,
avg(ss_coupon_amt) agg3,
avg(ss_sales_price) agg4
from store_sales, customer_demographics, date_dim, item, promotion
where ss_sold_date_sk = d_date_sk and
ss_item_sk = i_item_sk and
ss_cdemo_sk = cd_demo_sk and
ss_promo_sk = p_promo_sk and
cd_gender = 'M' and
cd_marital_status = 'M' and
cd_education_status = '4 yr Degree' and
(p_channel_email = 'N' or p_channel_event = 'N') and
d_year = 2001
group by i_item_id
order by i_item_id
limit 100;
```
`spark-defaults.conf` file:
```
spark.master yarn-client
spark.executor.instances 20
spark.driver.memory 16g
spark.executor.memory 30g
spark.executor.cores 5
spark.default.parallelism 100
spark.sql.shuffle.partitions 100000
spark.serializer
org.apache.spark.serializer.KryoSerializer
spark.driver.maxResultSize 0
spark.rpc.netty.dispatcher.numThreads 8
spark.executor.extraJavaOptions -XX:+UseG1GC
-XX:+UseStringDeduplication -XX:G1HeapRegionSize=16M -XX:MetaspaceSize=256M
spark.cleaner.referenceTracking.blocking true
spark.cleaner.referenceTracking.blocking.shuffle true
```
Performance test results are as follows
[SPARK-17930](https://github.com/witgo/spark/tree/SPARK-17930)|
[ed14633](https://github.com/witgo/spark/commit/ed1463341455830b8867b721a1b34f291139baf3])
------------ | -------------
54.5 s|231.7 s
## How was this patch tested?
Existing tests.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/witgo/spark SPARK-17930
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/15512.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #15512
----
commit 037871d8843760fbbdeab344d8228bfaeba6f6ae
Author: Guoqiang Li <wi...@qq.com>
Date: 2016-10-16T03:18:00Z
The SerializerInstance instance used when deserializing a TaskResult is not
reused
----
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