1333613 - hgweb and hgssh machines have / mounted with atime enabled

Status: RESOLVED WONTFIX

(Developer Services :: Mercurial: hg.mozilla.org, defect)

Description

[Gregory Szorc [:gps]]

hgweb and hgssh have / mounted with the "defaults" mount options, which include "relatime."

Unless there is an arcane requirement to have it, recording access times is unnecessary and just adds overhead. We should add "noatime" to the mount options to disable it.

Comment 1

[Kendall Libby [:fubar] (he/him)]

You could probably convince me that's useful on hgweb, where all of the repos are actually under /, but on hgssh they're aren't so what do we actually gain by deviating from default CentOS behavior?

Comment 2

[Gregory Szorc [:gps]]

We gain performance and extend the lifetime of the underlying SSDs. Servicing a clone or pull will potentially access thousands of files. While I suspect the corresponding atime updates will be buffered, that's still a lot of avoidable I/O writes. And IIRC the SSDs in the hgweb machines are optimized for reads and don't have as many write cycles. So atimes will reduce their lifetime.

Comment 3

[Gregory Szorc [:gps]]

FWIW the default mount option of "relatime" isn't as evil as "atime." So this is not as urgent as I thought it was. It is somewhat annoying though.