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WANG Ji 王冀 ijingo

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@jaskiratr
jaskiratr / chmod-400.cmd
Created June 29, 2018 01:03
Set permission of file equivalent to chmod 400 on Windows.
# Source: https://stackoverflow.com/a/43317244
$path = ".\aws-ec2-key.pem"
# Reset to remove explict permissions
icacls.exe $path /reset
# Give current user explicit read-permission
icacls.exe $path /GRANT:R "$($env:USERNAME):(R)"
# Disable inheritance and remove inherited permissions
icacls.exe $path /inheritance:r
@KartikTalwar
KartikTalwar / Documentation.md
Last active February 28, 2025 10:57
Rsync over SSH - (40MB/s over 1GB NICs)

The fastest remote directory rsync over ssh archival I can muster (40MB/s over 1gb NICs)

This creates an archive that does the following:

rsync (Everyone seems to like -z, but it is much slower for me)

  • a: archive mode - rescursive, preserves owner, preserves permissions, preserves modification times, preserves group, copies symlinks as symlinks, preserves device files.
  • H: preserves hard-links
  • A: preserves ACLs
@jboner
jboner / latency.txt
Last active April 23, 2025 18:02
Latency Numbers Every Programmer Should Know
Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference 0.5 ns
Branch mispredict 5 ns
L2 cache reference 7 ns 14x L1 cache
Mutex lock/unlock 25 ns
Main memory reference 100 ns 20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy 3,000 ns 3 us
Send 1K bytes over 1 Gbps network 10,000 ns 10 us
Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD