Messages in this thread | | | Subject | Re: [PATCH] IB/ehca: Serialize HCA-related hCalls on POWER5 | From | Joachim Fenkes <> | Date | Mon, 10 Dec 2007 18:59:16 +0100 |
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Hi, guys,
> We're taking this to the firmware architects at the moment, but they're not > very fond of the idea of reporting the absence of bugs through capability > flags, as this could quickly lead to the exhaustion of flag bits. We'll let > the discussion stew for a bit, but if we don't get this flag, we'll have to > resort to the CPU features.
The architects have spoken, and we're getting a capability flag for this. I'll repost my patch with new autodetection code that doesn't involve checking the processor version.
> > > Regarding the performance problem, have you checked whether converting all > > > your spin_lock_irqsave to spin_lock/spin_lock_irq improves your performance > > > on the older machines? Maybe it's already fast enough that way. > > > > It does seem that the only places that the hcall_lock is taken also > > use msleep, so they must always be in process context. So you can > > safely just use spin_lock(), right? > > As Arnd said, there are hCalls that will never return H_LONG_BUSY_*, such as > H_QUERY_PORT and chums, so they will never sleep. The surrounding functions, > though, are not prepared to be called from interrupt context (GFP_KERNEL comes > to mind), so I agree that a simple spin_lock() will suffice. Thanks, Arnd, for > pointing this out.
As I pointed out in my earlier mail, there's still an issue with map_phys_fmr possibly sleeping. Let's keep the irqsave for the time being and revisit this part once we find a solution to map_phys_fmr.
Regards, Joachim
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