Messages in this thread | | | Date | Fri, 9 Jun 2006 09:00:00 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [PATCH 01/14] Per zone counter functionality |
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On Fri, 9 Jun 2006, Andi Kleen wrote:
> It would be nicer to use some variant of local_t - then you could do that > without turning off interrupts (which some CPUs like P4 don't like) > > There currently is not 1 byte local_t but it could be added. > > Mind you it would only make sense when most of the calls are not already > with interrupts disabled.
We have discussed this before and there is a comment in the patch:
+ * + * Some processors have inc/dec instructions that are atomic vs an interrupt. + * However, the code must first determine the differential location in a zone + * based on the processor number and then inc/dec the counter. There is no + * guarantee without disabling preemption that the processor will not change + * in between and therefore the atomicity vs. interrupt cannot be exploited + * in a useful way here. + */ +void __inc_zone_page_state(struct page *page, enum zone_stat_item item) +{ + struct zone *zone = page_zone(page); + s8 *p = diff_pointer(zone, item); + + (*p)++; + + if (unlikely(*p > STAT_THRESHOLD)) { + zone_page_state_add(*p, zone, item); + *p = 0; + } +}
AFAIK the restrictions on local_t use are such that is barely usable. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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