heroheman

Ranger Cheatsheet

General

Shortcut	Description
ranger	Start Ranger
Q	Quit Ranger
R	Reload current directory
?	Ranger Manpages / Shortcuts

djspiewak

Thread Pools

Thread pools on the JVM should usually be divided into the following three categories:

1. CPU-bound
2. Blocking IO
3. Non-blocking IO polling

Each of these categories has a different optimal configuration and usage pattern.

svanoort

# Base settings and GC logging
-server -XX:+AlwaysPreTouch  # First should be default, but we make it explicit, second pre-zeroes memory mapped pages on JVM startup -- improves runtime performance
# -Xloggc:gc-%t.log  # CUSTOMIZE LOCATION HERE - $path/gc-%t.log -- the %t in the gc log file path is so we get a new file with each JVM restart
-XX:NumberOfGCLogFiles=5 -XX:+UseGCLogFileRotation -XX:GCLogFileSize=20m # Limits the number of files, logs to folder 
-XX:+PrintGC -XX:+PrintGCDateStamps -XX:+PrintGCDetails -XX:+PrintHeapAtGC -XX:+PrintGCCause
-XX:+PrintTenuringDistribution -XX:+PrintReferenceGC -XX:+PrintAdaptiveSizePolicy # gather info on object age & reference GC time for further tuning if needed.

# G1 specific settings -- probably should be default for multi-core systems with >2 GB of heap (below that, default is probably fine)
-XX:+UseG1GC
-XX:+UseStringDeduplication

NikolayS

-- Installs "file_fdw" extension and creates foreign table to work with data from CSV file.
-- See also the comment below which helps to automate the process for Google Spreadsheets
-- Another option would be using Multicorn for Google Spreadsheets, but it requires additional steps  
-- (see https://wiki.postgresql.org/wiki/Foreign_data_wrappers).

create extension file_fdw;
create server "import" foreign data wrapper file_fdw;

create foreign table "table1" (
  col1 text,

matthewmccullough

Git Compression of Blobs and Packfiles.

Many users of Git are curious about the lack of delta compression at the object (blob) level when commits are first written. This efficiency is saved until the pack file is written. Loose objects are written in compressed, but non-delta format at the time of each commit.

A simple run though of a commit sequence with only the smallest change to the image (in uncompressed TIFF format to amplify the observable behavior) aids the understanding of this deferred and different approach efficiency.

The command sequence:

Create the repo: