Re: RELENG_4 -> 5 -> 6: significant performance regression


----- Original Message ----- From: "Bartosz Fabianowski" <freebsd@xxxxxxxxx>
To: <ml@xxxxxxxx>
Cc: <freebsd-stable@xxxxxxxxxxx>
Sent: Thursday, April 27, 2006 3:40 PM
Subject: Re: RELENG_4 -> 5 -> 6: significant performance regression


You wrote that Giant is needed in 6.0 and now you write it has been
removed.

In 4.x, every UFS write requires the Giant lock. In 6.x, Giant is not normally required, making file system operations faster. When you enable QUOTA, you basically get back to the 4.x behavior where Giant is needed for each write. This is why in 6.x UFS will normally be faster but if you enable QUOTA, you lose the newly gained performance again.

In that case the test was correct the question stands at least on that point.
If quota isn't mpsafe yet, that's fine. It just means that performance should still be only about the same as on 4 while quota is enabled.
Removing a feature you had before is no answer to this question.
Removing an expensive new feature that didn't exist before could be.

Is it maybe simply some expected/known extra overhead that is ok because it's understood that it's only for a while, while mpsafe quota gets polished and no one is expected to switch production boxes over until after?
And once we have mpsafe quota we'll have a faster fs that still delivers the same features?

Brian K. White -- brian@xxxxxxxxx -- http://www.aljex.com/bkw/
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filePro BBx Linux SCO FreeBSD #callahans Satriani Filk!

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