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Back to basics – gprof PT1 (generating a profile)
A while ago at work we were discussing the pros and cons of the classic Linux profiler gprof… What are…
Tag: linux
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Effect of POSIX_FADV_SEQUENTIAL and POSIX_FADV_RANDOM on IO performance.
Previously we looked at how the POSIX_FADVISE_DONTNEED hint influences the Linux page cache when doing IO via a filesystem. Here…
1 min read
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Using fio to read from Linux buffer-cache
Sometimes we want to read from the Linux cache rather than the underlying device using fio. There are couple of…
1 min read
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Understanding QEMU devices
Not sure where I came across this, but it is an excellent description of QEMU (and virtualization in general). I…
1 min read
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A Nutanix / Prometheus exporter in bash
Overview For a fun afternoon project, how about a retro prometheus exporter using Apache/nginx, cgi-bin and bash!? About prometheus format…
1 min read
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Linux memory monitoring (allocations Vs usage)
How to use some of Linux’s standard tools and how different types of memory usage shows up. Examples of using…
1 min read
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Using iperf multi-stream may not work as expected
Running iperf with parallel threads TL;DR – When running iperf with parallel threads/workers the -P option must be specified after…
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Generate load on Microsoft SQLserver Windows from HammerDB on Linux
Often it’s nice to be able to drive Windows applications and databases from Linux, especially if you are more comfortable…
1 min read
5
Create a Linux VM with KVM in 6 easy steps
A Step-by-step guide to creating a Linux virtual machine on a Linux host with KVM,qemu,libvirt and ubuntu cloud images.
1 min read
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Using cloud-init with AHV command line
TL;DR Using cloud-init with AHV is conceptually identical to using KVM/QEMU- we need to use a few different tools with…
1 min read
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Why does my SSD not issue 1MB IO’s?
First things First Why do we tend to use 1MB IO sizes for throughput benchmarking? To achieve the maximum throughput…
2 min read
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Duplicate IP issues with Linux and virtual machine cloning.
TL;DR – Some modern Linux distributions use a newer method of identification which, when combined with DHCP can result in…
2 min read
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Performance gains for postgres on Linux with hugepages
For this experiment I am using Postgres v11 on Linux 3.10 kernel. The goal was to see what gains can…
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The return of misaligned IO
We have started seeing misaligned partitions on Linux guests runnning certain HDFS distributions. How these partitions became mis-aligned is a…