Red Hat Performance Blog: March 2014 archives

  • The Right Performance Tool for the Task

    As an engineer who works on performance tools at Red Hat, I often get seemingly simple questions along the lines of, "How do I get performance tool X to collect Y data?" Unfortunately, many times the answer is that "tool X does not measure Y." This leads to a dicussion about the performance problem being investigated. With additional background information, it becomes much easier to suggest more promising tools and techniques to get the desired measurements. Given the number of performance...
    Posted 2014-03-31T18:04:57+00:00 - 0
  • Determining Whether an Application Has Poor Cache Performance

    Modern computer systems include cache memory to hide the higher latency and lower bandwidth of RAM memory from the processor. The cache has access latencies ranging from a few processor cycles to 10 or 20 cycles, rather than the hundreds of cycles needed to access RAM. If the processor must frequently obtain data from the RAM rather than the cache, performance will suffer. With Red Hat Enterprise Linux 6 and later distributions, the system use of cache can be measured with the perf utility...
    Posted 2014-03-26T20:39:35+00:00 - 0
  • Examining Huge Pages or Transparent Huge Pages Performance

    All modern processors use page-based mechanisms to translate the user-space processes virtual addresses into physical addresses for RAM. The pages are commonly 4KB in size, and the processor can hold a limited number of virtual-to-physical address mappings in the Translation Lookaside Buffers (TLB). The number of TLB entries ranges from tens to hundreds of mappings. This limits a processor to a few megabytes of memory it can address without changing the TLB entries. When a virtual-to-physical...
    Posted 2014-03-26T20:35:16+00:00 - 0