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Bert Scalzo on Linux Maximus for Oracle

 
Mr. Bert Scalzo, a respected Oracle professionals, has published an excellent paper titled "Linux Maximus, Part 1: Gladiator-like Oracle Performance":
 
 
Scalzo notes that Linux does not perform super-fast without proper configuration and that tweaking Linux and Oracle can result in a 1,000% performance improvement:
"Believe it or not, it's quite easy to get upwards of 1000% database improvement through proper Linux tuning and database configuration for Linux."
In the section titled "DB low hanging fruit", Mr. Scalzo notes that doubling the database blocksize improved TPC-C throughout:
"Even a PC with its limited bus and I/O capabilities can reap huge benefits from a larger block size. The load time improved over 138%, with no detriment to the TPS. "
Scalzo also shows how adjusting initialization and tablespace parameters improved Oracle performance on Linux:
 
"We got improvements of 342% for the load time and 24% for the TPS; not bad for requiring absolutely no extensive or detailed performance monitoring."
Linux Kernel Tuning for Oracle
 
Mr Scalzo then focuses on tuning the Linux filesystem I/O performance:
"vm.bdflush = 100 1200 128 512 15 5000 500 1884 2

Where according to /usr/src/Linux/Documentation/sysctl/vm.txt:

The first parameter 100 %

: governs the maximum number of dirty buffers in the buffer cache. Dirty means that the contents of the buffer still have to be written to disk as opposed to a clean buffer, which can just be forgotten about. Setting this to a high value means that Linux can delay disk writes for a long time, but it also means that it will have to do a lot of I/O at once when memory becomes short. A low value will spread out disk I/O more evenly.

The second parameter 1200

ndirty: gives the maximum number of dirty buffers that bdflush can write to the disk in one time. A high value will mean delayed, bursty I/O, while a small value can lead to memory shortage when bdflush isn't woken up often enough.

The third parameter 128

nrefill: the number of buffers that bdflush will add to the list of free buffers when refill_freelist() is called. It is necessary to allocate free buffers beforehand, as the buffers often are of a different size than the memory pages, and some bookkeeping needs to be done beforehand. The higher the number, the more memory will be wasted and the less often refill_freelist() will need to run.

refill_freelist() 512

: when this comes across more than nref_dirt dirty buffers, it will wake up bdflush.

age_buffer 50*HZ, age_super parameters 5*HZ

: govern the maximum time Linux waits before writing out a dirty buffer to disk. The value is expressed in jiffies (clockticks); the number of jiffies per second is 100. Age_buffer is the maximum age for data blocks, while age_super is for filesystem metadata.

The fifth 15 and the last two parameters 1884 and 2

: unused by the system so we don't need to change the default ones."


 

 
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