Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 6 Jun 2016 14:20:32 -0700 | Subject | Re: performance delta after VFS i_mutex=>i_rwsem conversion |
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On Mon, Jun 6, 2016 at 2:13 PM, Waiman Long <waiman.long@hpe.com> wrote: > > The tricky part about optimistic spinning in rwsem is that we don't know for > sure if any of the lock holding readers is running or not.
I'm notm sure how common the reader-vs-writer contention is, at least for the new inode use. I'm sure you can trigger it with crazy benchmarks, but I wouldn't worry about it unless people start complaining.
The writer-writer case is easy to trigger with write-heavy loads (ok, rename/unlink in this case). Are there real loads where there are lots of concurrent lookup and writes? I really don't know (note that "lookup" needs to be uncached and actually hit the lowlevel filesystem for the locking to even trigger in the first place).
I guess some "concurrent readdir with unlink" load would show that behavior, but is it _realistic_? No idea. Let's not worry about it too much until somebody shows a reason to worry.
Linus
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