A little bit of lazy and busy in the beginning of 2012, I haven’t written too much. Yep, I just got another session of internship in Google this summer. What I’ve heard so far is only that I will work in the Ads backend team to optimize their map-reduce stuff…It sounds like a awesome job, [...]
Author Archives: xulei
Dynamically set CPU offline on Linux
Linux provides a mechanism to hotplug a CPU (core) online or offline during the runtime, which is very convenient for me to dynamically adjust the CPU topology. As usual, I have written a python script (Link: gist:1331343) to make this manually task easy. This script accepts similar parameters as taskset(8): # Set core 1,2,3,5,6,7,9,12 online, [...]
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HomeNAS reborn with ZFS
After came back from California, I bought a HP ProLiant MicroServer for its 4 hard drive bays. The machine was upgraded to 5(1+4) GB ECC RAMs, and added two more Seagate Barracuda Green 1.5TB 5900RPM HDDs. Without any confidence of storing important data (e.g family photos, research data and drafts) on the 3 years old [...]
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Google intern summary 1
Three busy weeks have passed by. For most of the time, I was attending tutorials, reading documents and at the end of this period, I was writing documents. Yes, no a single line of code I wrote. Google has fantastic infrastructures for developments and a bunch of awesome people giving tutorials to us nooglers (a.k.a [...]
Got google summer internship
I am so excited to get the google summer internship this year for a great matched team, the storage team for Google Apps. Two back-to-back tech phone screens were taken at the last Monday (March 21). I felt good about the most of the questions except the last one, for which my brain was shortcut [...]
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Reading: Cheap and Large CAMS for High Performance Data-Intensive Network Systems (NSDI’10)
This paper presents how to build cheap and large CAMs (what’s CAM?) using a combination of DRAM and flash memory(SSD) to balance the cost and query latency. The main approach of this work is building multiple small hash tables, which are stored on SSD, and holding a two-level bloom-filter in RAM to provide fast hash [...]
Developing environment for solo developer
Yes, I am still a computer science Ph.D student right now. Therefore, for my long-term research projects, there is nobody taking charge of building automatically test environments, document management, several platform configurations and so on. I have to build my own to fit my specific workloads: typically a project starts from collecting ideas (head storms), [...]
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Note: Move MySQL database to another location
For the purpose to evaluate the performance of MySQL database on Ubuntu, I have to move it to an separated disk. I write the steps here for future use: mkdir /mnt/test/mysql and chmod -R mysql:mysql /mnt/test/mysql Stop mysql cp -rp /var/lib/mysql/mysql /var/lib/mysql/otherdb /mnt/test/mysql Modify /etc/mysql/my.cnf, find the line with datadir = /var/lib/mysql , then change [...]
A sed script to extract file name from trace file
The following script is used to extract the full path from a file. sed -En ‘s#^[^/]+(/([^ ])+).+#\1#gp’ < trace.txt
Reading: Debunking the 100X GPU vs. CPU Myth
This paper comes from ISCA’10. This paper re-evaluates the performance gap, especially for high throughput computing, between CPU and GPU. Contrast to the previous papers it mentioned claimed 100x performance differences between CPU and GPU, with appropriate optimizations, the performance gap between CPU (Intel Core i7 960) and Nvidia GTX280 narrows to only 2.5x on [...]