Hi Gopal, Thanks for your reply. >For the Hadoop version, we will upgrade it to 2.8 later. >In our test, we found the shuffle stage of LLAP is very slow. Whether need to >configure some related shuffle value or not? And we get the following log >from the LLAP daemon in shuffle stage: 2017-11-23T12:48:39,367 INFO [New I/O worker #120 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:39,656 INFO [New I/O worker #121 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:39,698 INFO [New I/O worker #122 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:39,849 INFO [New I/O worker #123 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:39,859 INFO [New I/O worker #124 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:40,037 INFO [New I/O worker #125 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:40,141 INFO [New I/O worker #126 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:40,298 INFO [New I/O worker #127 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header... 2017-11-23T12:48:40,718 INFO [New I/O worker #128 ()] org.apache.hadoop.hive.llap.shufflehandler.ShuffleHandler: Setting connection close header...
>Now " hive.llap.execution.mode" have "auto,none,all,map,only" mode. About the >four mode, do you have some suggestions? Whether the "all" mode can gain the >best performance or not? And how the "auto" and "only" mode work? Regards, Jia Ke -----Original Message----- From: Gopal Vijayaraghavan [mailto:gop...@apache.org] Sent: Thursday, November 23, 2017 4:03 AM To: user@hive.apache.org Subject: Re: Hive +Tez+LLAP does not have obvious performance improvement than HIVE + Tez Hi, > With these configurations, the cpu utilization of llap is very low. Low CPU usage has been observed with LLAP due to RPC starvation. I'm going to assume that the build you're testing is a raw Hadoop 2.7.3 with no additional patches? Hadoop-RPC is single-threaded & has a single mutex lock in the 2.7.x branch, which is fixed in 2.8. Can you confirm if you have backported either https://issues.apache.org/jira/browse/HADOOP-11772 or https://issues.apache.org/jira/browse/HADOOP-12475 to your Hadoop implementation? The secondary IO starvation comes from a series of HDFS performance problems which are easily worked around. Here's the root-cause https://issues.apache.org/jira/browse/HDFS-9146 The current workaround is to make sure that the HDFS & Hive user has a limits.d entry to allow it to open a large number of sockets (which are fds). https://github.com/apache/ambari/blob/trunk/ambari-server/src/main/resources/common-services/HDFS/2.1.0.2.0/package/templates/hdfs.conf.j2 + https://github.com/apache/ambari/blob/trunk/ambari-server/src/main/resources/common-services/HIVE/2.1.0.3.0/package/templates/hive.conf.j2 This increases the FD limit for Hive & HDFS users (YARN also needs it, in case of Tez due to shuffle being served out of the NodeManager). After increasing the FDs, LLAP is fast enough to run through 128 socket openings within the Linux TCP MSL (60 seconds) The RHEL default for somaxconn is 128, which causes 120s timeouts when HDFS silently loses packets & forces the packet timeout to expire before retrying. To know whether the problem has already happened, check the SNMP traps # netstat -s | grep "overflow" <n> times the listen queue of a socket overflowed Or to know when the SYN flood issue has been worked around by the kernel with cookies. # dmesg | grep cookies After this, you get hit by the DNS starvation within LLAP where the DNS server traffic (port 53 UDP) gets lost (or the DNS server bans an IP due to massive number of packets). This is a JDK internal detail, which ignores the DNS actual TTL values, which can be worked around by running nscd or sssd on the host to cache dns lookups without generating UDP network packets constantly. If you need more detail on any of these, ask away. I've had to report and get backports for several of these issues into HDP (mostly because perf issues are not generally community backports & whatever has good workarounds remain off the priority lists). Cheers, Gopal
