Instead of the easily brute-forceable one-pass MD5/AES128 password protection format used by SSH per default, you should use the PKCS#8 format to store your private key files. PKCS#8 allows to choose proper key-derivation functions and encryption schemes (for example PBKDF2 and PBES2).
The following commands convert an existing password protected SSH private key file to PKCS#8 format (using PBKDF2, PBES2 and AES-256):
mv ~/.ssh/id_rsa{,.old}
openssl pkcs8 -topk8 -v2 aes256 -in ~/.ssh/id_rsa.old -out ~/.ssh/id_rsa
chmod 600 ~/.ssh/id_rsa
rm ~/.ssh/id_rsa.old
(via Martin Kleppmann)
Found this neat trick in Brendan Gregg's Blazing Performance with Flame Graphs talk.
Switching to LANG=C improved performance by 2000x
In a quick test I directly got a performance gain of factor 50.22.
This is quite an achievement for only changing one environment variable.
real:~# du -sh /var/log/querylog
148M /var/log/querylog
real:~# time grep -i e /var/log/querylog > /dev/null
real 0m12.807s
user 0m12.437s
sys 0m0.068s
real:~# time LANG=C grep -i e /var/log/querylog > /dev/null
real 0m0.255s
user 0m0.196s
sys 0m0.052s
I suspect that the performance gain may vary quite a lot depending on the search pattern.
Also, please note that this trick only works when you know that the involved files and search patterns are ASCII only.
(via Standalone Sysadmin)