Date: Wed, 15 Aug 2007 13:42:18 -0400 From: Kris Kennaway <kris@obsecurity.org> To: Artem Kuchin <matrix@itlegion.ru> Cc: freebsd-stable@freebsd.org Subject: Re: twa is giant locked in 7-Current or everywhere? Message-ID: <20070815174218.GB71910@rot26.obsecurity.org> In-Reply-To: <000b01c7df5f$0ee4eec0$0c00a8c0@Artem> References: <000b01c7df5f$0ee4eec0$0c00a8c0@Artem>
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On Wed, Aug 15, 2007 at 09:09:33PM +0400, Artem Kuchin wrote:
> Hi!
>
> When i installed twas driver on 6.2-STABLE it said
> [FAST]
>
> i presumed that it measn that twa is giant-lock free.
>
> Now, after installing 7-CURRENT i see
>
> Aug 15 17:00:02 omni3 kernel: 3ware device driver for 9000 series storage
> controllers, version: 3.70.03.007
> Aug 15 17:00:02 omni3 kernel: twa0: <3ware 9000 series Storage Controller>
> port 0x3000-0x30ff mem 0x88000000-0x89ffffff,0x8a200000-0x8a200fff irq 16
> at devic
> Aug 15 17:00:02 omni3 kernel: twa0: [GIANT-LOCKED]
> Aug 15 17:00:02 omni3 kernel: twa0: [ITHREAD]
>
>
> So, it says GIANT-LOCKED and then ITHREAD.
>
> Apparently, i have no real understaning what those words mean.
> COuld anyone explain the meaning of
>
> FAST
> ITHREAD
>
> Giant-locked is self explanatory and.. bad.
I think 6.x doesn't display the GIANT-LOCKED messages because users
were freaking out too much after they were added at an earlier point
in 6.x development ("Q: why is this driver suddenly giant locked?" "A:
It's always been giant locked, now this fact is displayed as a note to
developers.").
While it's true that a non-giant locked driver would be better, it's
not as bad as you might think because almost nothing else requires
giant for most workloads thesedays (see
http://wiki.freebsd.org/SMPTODO), so in those workloads performance
will not be worse because of it. If you are really bothered by this
you can enable mutex profiling to check how much of a problem it is
for you.
Kris
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