Messages in this thread | | | Date | Fri, 23 Sep 2005 12:16:18 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [patch 0/6] mm: alloc_percpu and bigrefs |
| |
On Fri, 23 Sep 2005, Andrew Morton wrote:
> big deal. Given that alloc_percpu() is already numa-aware, is that extra > cross-node fetch and pointer hop really worth all that new code? The new > version will have to do a tlb load (including a cross-node fetch) > approximately as often as the old version will get a CPU cache miss on the > percpu array, maybe?
The current alloc_percpu() is problematic because it has to allocate entries for all cpus even those who are not online yet. There is no way to track alloc_percpu entries and therefore no possibility of adding an entry for a processor if one comes online or for removing one when a processor goes away.
An additional complication is the allocation of per cpu entries for processors whose memory node are not online. The current implementation will fall back on a unspecific allocation but this means that the placement of the per cpu entries will not be on the node of the processor! - 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/
| |