Messages in this thread |  | | From | David Howells <> | Subject | Re: [PATCH] FRV: do_gettimeofday() should no longer use tickadj | Date | Mon, 11 Sep 2006 11:46:44 +0100 |
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Ingo Molnar <mingo@elte.hu> wrote:
> i cannot find Thomas' recent 2.6 one (Thomas, do you have a link to > it?), but i did one 5 years ago: > > http://people.redhat.com/mingo/irq-rewrite-patches/irq-cleanup-2.4.15-B1.bz2 > > in general it's a large but otherwise pretty dumb patch.
I wrote my own patch to test this last Friday. I found that removing all the regs pointer passing from the interrupt code reduced interrupt entry with a warm cache by 1 cpu cycle out of 87, and interrupt exit by 19 cycles out of 99.
I can't tell from that exactly how many instructions/memory accesses have been removed since the FRV permits two instructions to be executed in one cycle under some circumstances, and two registers to be stored/loaded in one instruction.
But the main gain in the exit path has to be due to recovery of the clobbered regs parameter due to a call inside a loop, possibly in handle_IRQ_event().
I'd expect i386 to do better in cycle reduction because it has fewer registers and so getting one back should gain more.
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