rich7420 commented on PR #11151:
URL: https://github.com/apache/ozone/pull/11151#issuecomment-5461217322
Quick JMH of a page-cache-hot `ReadChunk` (open + read) with the per-op
`getChunkDir` stat (old) vs the cached dir (new), JDK 21 / macOS (5 forks x 5,
n=25):
```
chunk old new saved
4KB 11.2 us 9.35 us 1.85 us (~16%)
1MB 36.0 us 33.7 us 2.26 us (~6%)
```
The removed work is ~one stat plus a `File` allocation (~2 us, roughly
constant), so it is a meaningful fraction for small cached reads and shrinks as
the read grows. On the read path the stat is pure added work (the read
otherwise goes straight to open()). No fsync in this run, and macOS stat is
pricier than Linux, so the fraction is an upper bound. Standalone JMH, not part
of the PR.
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: [email protected]
For queries about this service, please contact Infrastructure at:
[email protected]
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
