Brendan Gregg

SEPTEMBER 25, 2021

These strange questions came to the fore back in 2014 when Netflix was switching services from CentOS Linux to Ubuntu, and I helped debug several weird performance issues including one I'll describe here. As a Xen guest, this profile was gathered using perf(1) and the kernel's software cpu-clock soft interrupts, not the hardware NMI.

Speed 126

Speed Java AWS Virtualization 126

SQL Performance

MARCH 17, 2020

Back in 2014, I wrote an article called Performance Tuning the Whole Query Plan. Finding a small number of distinct values might seem like quite a specific requirement, but I have come across it fairly frequently over the years, usually as part of tuning a larger query. Test Environment. Final Thoughts.

Servers 86

Servers Tuning Database Efficiency 86

SQL Performance

JUNE 21, 2019

For SQL Server 2008R – 2014, you could lower this threshold using trace flag 2371. While hardware such as intelligent SANs, Solid State Disk, and other advancements have helped speed things up, wasted space in index can translate to wasted space in the buffer pool as well as wasting more I/O. That can take a long time on larger tables.

Servers 49

Servers Azure Hardware Database 49

Brendan Gregg

SEPTEMBER 25, 2021

These strange questions came to the fore back in 2014 when Netflix was switching services from CentOS Linux to Ubuntu, and I helped debug several weird performance issues including one I'll describe here. As a Xen guest, this profile was gathered using perf(1) and the kernel's software cpu-clock soft interrupts, not the hardware NMI.

Speed 40

Speed Java AWS Virtualization 40

Brendan Gregg

SEPTEMBER 5, 2017

Linux has been adding tracing technologies over the years: kprobes (kernel dynamic tracing), uprobes (user-level dynamic tracing), tracepoints (static tracing), and perf_events (profiling and hardware counters). Outside of EC2, many other providers are deploying on KVM. Or, from a different point of view, Solaris was less secure.)

Virtualization 76

Virtualization AWS Engineering Hardware 76

SQL Performance

MARCH 8, 2021

SQL Server 2014 SP2 and later produce runtime (“actual”) execution plans that can include elapsed time and CPU usage for each execution plan operator (see KB3170113 and this blog post by Pedro Lopes). This can make it difficult to draw sound performance-tuning conclusions. The clock keeps running at the same rate even during sleep.

Servers 95

Servers Tuning Architecture Processing 95