Messages in this thread | | | Subject | Re: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI drivers | From | Xiaofei Tan <> | Date | Thu, 25 Feb 2021 10:37:26 +0800 |
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Hi Geert,
On 2021/2/24 17:41, Geert Uytterhoeven wrote: > Hi Xiaofei, > > On Sun, Feb 7, 2021 at 12:46 PM Xiaofei Tan <tanxiaofei@huawei.com> wrote: >> Replace spin_lock_irqsave with spin_lock in hard IRQ of SCSI drivers. >> There are no function changes, but may speed up if interrupt happen >> too often. > > I'll bite: how much does this speed up interrupt processing? > What's the typical cost of saving/disabling, and restoring interrupt > state?
It could only take a few CPU cycles. So there is little benefit for speeding up interrupt processing.You could take them as cleanup.
Is removing this cost worth the risk of introducing subtle > regressions on platforms you cannot test yourself? >
Currently, only found M68K platform support that high-priority interrupt preempts low-priority. No other platform has such services. Therefore, these changes do not affect non-M68K platforms.
For M68K platform, no one report such interrupt preemption case in these SCSI drivers.
> BTW, how many of these legacy SCSI controllers do you have access to? >
Actually, no.
> Thanks for your answers! > > Gr{oetje,eeting}s, > > Geert >
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