Messages in this thread Patch in this message | | | From | chris.higgins@horizon ... | Subject | PATCH: kernel/sched.c - Optimisation of some variable assignments | Date | Mon, 05 Mar 2001 10:06:15 +0000 |
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I was reading through sched.c and noticed two places where variable assignments occur immediately prior to 'if(test) goto label:' statements. If the test is TRUE, then the jump happens and in both cases the variables are either not used, or immediately over-written..
So I've re-sequenced the two sets of statements to 'test then assign' rather than 'assign regardless, then test'.
I presume that the C compiler is optimising this out, but not all platforms may been seeing this... It's probably only going to save a couple of cycles on any iteration through the scheduler, but the more available for everyone else the better :)
--- kernel/sched.c.orig Fri Feb 9 19:37:03 2001 +++ kernel/sched.c Sun Mar 4 20:27:42 2001 @@ -507,11 +507,11 @@ if (!current->active_mm) BUG(); need_resched_back: + if (in_interrupt()) + goto scheduling_in_interrupt; prev = current; this_cpu = prev->processor; - if (in_interrupt()) - goto scheduling_in_interrupt; release_kernel_lock(prev, this_cpu); @@ -553,10 +553,10 @@ /* * Default process to select.. */ - next = idle_task(this_cpu); - c = -1000; if (prev->state == TASK_RUNNING) goto still_running; + next = idle_task(this_cpu); + c = -1000; still_running_back: list_for_each(tmp, &runqueue_head) {
--END-OF-PATCH---
-- ** Chris Higgins e: chris.higgins at horizon.ie ** ** Technical Business Development tel: +353-1-6204916 ** ** Horizon Technology Group fax: +353-1-6204949 **
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