Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory
From: Nishanth Aravamudan <hidden>
Date: 2014-01-25 00:17:08
Also in:
linux-mm
Possibly related (same subject, not in this thread)
- 2014-02-07 · Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory · Joonsoo Kim <hidden>
- 2014-02-06 · Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory · Nishanth Aravamudan <hidden>
- 2014-01-24 · Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory · Wanpeng Li <hidden>
- 2014-01-24 · Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory · Wanpeng Li <hidden>
- 2014-01-21 · Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory · Wanpeng Li <hidden>
On 24.01.2014 [15:49:33 -0800], David Rientjes wrote:
On Fri, 24 Jan 2014, Nishanth Aravamudan wrote:quoted
quoted
I think the problem is a memoryless node being used for kmalloc_node() so we need to decide where to enforce node_present_pages(). __slab_alloc() seems like the best candidate when !node_match().Actually, this is effectively what Anton's patch does, except with Wanpeng's adjustment to use node_present_pages(). Does that seem sufficient to you?I don't see that as being the effect of Anton's patch. We need to use numa_mem_id() as Christoph mentioned when a memoryless node is passed for the best NUMA locality. Something like this:
Thank you for clarifying and providing a test patch. I ran with this on the system showing the original problem, configured to have 15GB of memory. With your patch after boot: MemTotal: 15604736 kB MemFree: 8768192 kB Slab: 3882560 kB SReclaimable: 105408 kB SUnreclaim: 3777152 kB With Anton's patch after boot: MemTotal: 15604736 kB MemFree: 11195008 kB Slab: 1427968 kB SReclaimable: 109184 kB SUnreclaim: 1318784 kB I know that's fairly unscientific, but the numbers are reproducible. For what it's worth, a sample of the unmodified numbers: MemTotal: 15317632 kB MemFree: 5023424 kB Slab: 7176064 kB SReclaimable: 106816 kB SUnreclaim: 7069248 kB So it's an improvement, but something is still causing us to (it seems) be pretty inefficient with the slabs.
quoted hunk ↗ jump to hunk
diff --git a/mm/slub.c b/mm/slub.c --- a/mm/slub.c +++ b/mm/slub.c@@ -2278,10 +2278,14 @@ redo: if (unlikely(!node_match(page, node))) { stat(s, ALLOC_NODE_MISMATCH); - deactivate_slab(s, page, c->freelist); - c->page = NULL; - c->freelist = NULL; - goto new_slab; + if (unlikely(!node_present_pages(node))) + node = numa_mem_id(); + if (!node_match(page, node)) { + deactivate_slab(s, page, c->freelist); + c->page = NULL; + c->freelist = NULL; + goto new_slab; + }
Semantically, and please correct me if I'm wrong, this patch is saying if we have a memoryless node, we expect the page's locality to be that of numa_mem_id(), and we still deactivate the slab if that isn't true. Just wanting to make sure I understand the intent. What I find odd is that there are only 2 nodes on this system, node 0 (empty) and node 1. So won't numa_mem_id() always be 1? And every page should be coming from node 1 (thus node_match() should always be true?) Thanks, Nish