Messages in this thread |  | | | Date | Fri, 27 Dec 2002 16:14:41 +0100 | | From | (Margit Schubert-While) | | Subject | Linux v2.5.53 pause et al |
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> [PATCH] reorder 'rep;nop;' in the spinlock macro > According to Intel's recommendation, 'rep;nop; should be called before testing > if the lock variable was modified (i.e. rep nop;cmp;jcc). > The current implementation does it the wrong way around: first test, then wait, then branch. > I've asked Asit Mallik from Intel, and he recommended to change it. > It should be at least consistent: Right now, spinlock uses 'cmp;rep nop;jcc', > rwlock uses 'rep nop;cmp;jcc'
Hmm. Unless I'm reading it wrong, this doesn't agree with the example 7-1c on page 7-14 of the P4 Optimization manual, or ?
This is also interesting - quote "The inc and dec instructions should always be avoided. Using add and sub instructions instead of inc and dec instructions avoid data dependence and improve performance."
Margit
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