Re: [Crash-utility] [PATCH] task.c: avoid unnecessary cpu cycles during init

> While stkptr_to_task does the job of trying to match a stack pointer > to a task, it runs through each task's stack to find whether the given > SP falls into its range. This can be a very expensive operation, if > the vmcore is from a system running too many tasks. It can get even > worse when the total number of CPUs on the system is in the order of > thousands. Given the expensive nature of the operation, it must be > optimized as much as possible. Possible options to optimize: > > 1) Get min & max of the stack range in first pass and use these > values against the given SP to decide whether or not to proceed > with stack lookup. > 2) Use multithreading to parallely update irq_tasks. > 3) Skip stkptr_to_task() when SP is 0 > > Though option 3 is a low hanging fruit, it significantly improved the > time taken between starting crash utility & reaching crash prompt. > Implement option 3 to optimize while listing the other two options > as TODO items for follow-up. It looks like on x86_64 the stkptr_to_task() is not called when starting session and I cannot test, but the patch looks safe enough. Acked-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; Lianbo, Bhupesh, this is not a fix but huge improvement for some machines or situations, so I'd like to pick it up for crash-7.2.9.

Could you ack this? and my patch for the compiler warnings?

Thanks, Kazu