Weiwei Jia

Weiwei Jia is a Ph.D. student in the Department of Computer Science at New Jersey Institute of Technology since 2016. His research interests are include storage systems, operating systems and computer systems.

how to install older version gcc/g++ in Ubuntu (other linux distro are similar)

When we compile some project, it needs older version gcc/g++ version. So how to insall older ones in ubuntu? Install older gcc/g++ version sudo apt-get install gcc-4.4 g++-4.4 g++-4.4-multilib gcc-4.4-multilib Set gcc/g++ version to be used automatically sudo update-alternatives –install /usr/bin/gcc gcc /usr/bin/gcc-4.4 50 sudo update-alternatives –install /usr/bin/g++ gcc /usr/bin/g++-4.4 50 You may need to […]

Printing “powernow-k8 transition frequency failed” after install XEN

After I installed XEN hypervisor, the tty0 (CTRL+ALT+F1) prints “powernow-k8 transition frequency failed” to STDOUT continously, how to solve it? sudo rmmod powernow_k8 From https://lists.debian.org/debian-user/2013/01/msg00754.html Answered by harryxiyou. How to make the settings persistent (take effect after reboot)? 1, Create script file ‘/etc/init.d/stop_pwoerk8.sh’ as follows. harry2vera@node1:/etc/init.d$ cat stop_pwoerk8.sh #! /bin/sh rmmod powernow_k8 2, Add the […]

Git-email cannot send email

As is known, git-send-email is easy to send patches to upstreams. However, now, I happen to following questions. How to solve it??? $ sudo git send-email –from=lgb.nwpu@gmail.com –to=ganeti-devel@googlegroups.com –in-reply-to=lgb.nwpu@gmail.com –subject=”[PATCH stable-2.10] Fix typos in doc/design-file-based-storage.rst” –smtp-server=/usr/bin/msmtp ./0001-fix-typos-in-design-file-based-storage.rst-doc.patch ./0001-fix-typos-in-design-file-based-storage.rst-doc.patch (mbox) Adding cc: Gangbiao Liu lgb.nwpu@gmail.com from line ‘From: Gangbiao Liu lgb.nwpu@gmail.com‘ From: lgb.nwpu@gmail.com To: ganeti-devel@googlegroups.com Cc: […]

What is Double-Blind review for a paper?

I want to submit my paper to NAS 2015 but I am confused about its double-blind review 盲审又包括单盲审(Single-Blind Peer Review, SBPR)和双盲审(Double-Blind Peer Review, DBPR)。双盲审是审者与作者之间互相都不知道彼此身份的匿名评审。在双盲审的过程中,中间组织者的规范和保密工作很重要。单盲审一般是审者知道作者的身份,而作者不知道审者是谁。 计算机有不少会议实行双盲评审。 Reference: http://emuch.net/html/201104/3022021.html Answered by harryxiyou.

how to integrate MySQL client into self designed database

Currently, I need to integrate MySQL client into SQLE as SQLE’s client. And then, we just need design/implement a translation layer to transfer MySQL protocol into SQLE engine part (KV+ internal exactly). Mysql-Proxy could solve this problem but it is complex to be only a MySQL server. Therefore, I remoduled MySQL-proxy to be more simple […]

How to merge git branches quickly and correctly

Suppose I have following branches harryxiyou@common_vm ~/forest/sqle/sqle/scripts $ git branch * dev-harry master rc After I did some changes on dev-harry branch, I wanted to merge dev-harry into rc branch. 1, git checkout rc 2, git merge dev-harry References:http://stackoverflow.com/questions/24147169/merge-two-remote-branches-in-githttps://www.atlassian.com/git/tutorials/using-brancheshttp://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging Answered by harryxiyou. I usually add –no-ff during git merge to force git to add a […]

What are the differences between database DDL and DML

Differences beween DDL (Data Definition Language) and DML (Data Manipulation Language) Data Definition Language (DDL) statements are used to define the database structure or schema. Data Manipulation Language (DML) statements are used for managing data within schema objects. References:http://www.orafaq.com/faq/what_are_the_difference_between_ddl_dml_and_dcl_commands Answered by harryxiyou.

how to remove specific directories recursively

How to remove .svn directories under hlfs dir recursively as follows. weiwei@weiwei-HP-Compaq-dx6128-MT-PX478AV:~/workshop1/hlfs > find ./ -name “.svn” ./test/build/.svn ./test/.svn ./output/conf/.svn ./output/lib32/.svn ./patches/.svn ./src/include/.svn ./src/include/api/.svn ./src/snapshot/.svn ./src/snapshot/unittest/build/.svn ./src/snapshot/unittest/.svn ./src/utils/.svn ./src/clean/Mapreducer/build/.svn ./src/clean/Mapreducer/.svn ./src/clean/.svn ./src/clean/unittest/.svn ./src/icache/.svn ./src/icache/unittest/.svn ./src/backend/.svn ./src/storage/.svn ./src/cache/.svn ./src/cache/unittest/.svn ./src/clone/.svn ./src/tools/.svn ./src/tools/unittest/.svn ./src/logger/.svn weiwei@weiwei-HP-Compaq-dx6128-MT-PX478AV:~/workshop1/hlfs > find ./ -name “.svn” | xargs rm -rf Answered by harryxiyou.

How to jump the GFW in mainland China

As is known, you cannot access some banned website in mainland China but we need them sometimes. 1, Download myentunnel from [1] 2, Config your myentunnel according to [2] 3, Download Firefox and config it in the light of [3] 4, Try facebook.com and check if it goes well References: [1] http://www.vpsmm.com/page/MyEnTunnel/ [2] http://linuxroad.blog.51cto.com/765922/1075684 Answered […]

How to config network in host (wireless network) for QEMU guest os

The host os is connected into network by wireless one so how to let its guest os connect network. Take [1] as a reference. I run it successfully with following steps. 1, create /etc/qemu-ifup script and chmod it. 2, start a qemu guest os with command sudo ./qemu/qemu-system-x86_64 -enable-kvm -m 1024 -drive file=marss_dram.qcow2 -vnc […]

What’s the difference between Reliability, Durability, and Availability for data storage system?

Some important concepts in distributed system like Hadoop distributed file system, Google file system and so on. Answer from http://www.quora.com/Whats-the-difference-between-Reliability-Durability-and-Availability-for-data-storage-system The difference between durability and availability is fairly simple. Durability is about what happens when all power goes out everywhere. Has all data been written to stable storage that doesn’t require power (e.g. disk/flash), in […]

How to import a googlecode git project to github project

I wanna migrate leveldb (code.google.com/p/leveldb) to my github repository. Create a new repo on github.com with this link https://help.github.com/articles/creating-a-new-repository git clone https://code.google.com/p/ project-name.git Set the remote origin url as follows: git remote set-url origin https://github.com/ username/ repo-name.git git pull to pull the latest. git push origin master after making local changes. This is the original […]

How does load balancing work inside of operating systems, Linux as an example

Introduction Load balance is used to rebalance the whole system resources (eg, CPU, memory, etc) so that system performance, scalability (in terms of no matter how many processes contend) and usability (in terms of idle resources can be used up immediately) will be improved. In this article, I mainly present how load balance for CPU […]