Subject: Re: [PATCH] slub: Don't throw away partial remote slabs if there is no local memory

From: Wanpeng Li <[email-masked]>
Date: Fri, 24 Jan 2014 11:14:12 +0800

On Fri, Jan 24, 2014 at 11:09:07AM +0800, Wanpeng Li wrote:
>Hi Christoph,
>On Mon, Jan 20, 2014 at 04:13:30PM -0600, Christoph Lameter wrote:
>>On Mon, 20 Jan 2014, Wanpeng Li wrote:
>>
>>> >+       enum zone_type high_zoneidx = gfp_zone(flags);
>>> >
>>> >+       if (!node_present_pages(searchnode)) {
>>> >+               zonelist = node_zonelist(searchnode, flags);
>>> >+               for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
>>> >+                       searchnode = zone_to_nid(zone);
>>> >+                       if (node_present_pages(searchnode))
>>> >+                               break;
>>> >+               }
>>> >+       }
>>> >        object = get_partial_node(s, get_node(s, searchnode), c, flags);
>>> >        if (object || node != NUMA_NO_NODE)
>>> >                return object;
>>> >
>>>
>>> The patch fix the bug. However, the kernel crashed very quickly after running
>>> stress tests for a short while:
>>
>>This is not a good way of fixing it. How about not asking for memory from
>>nodes that are memoryless? Use numa_mem_id() which gives you the next node
>>that has memory instead of numa_node_id() (gives you the current node
>>regardless if it has memory or not).
>
>diff --git a/mm/slub.c b/mm/slub.c
>index 545a170..a1c6040 100644
>--- a/mm/slub.c
>+++ b/mm/slub.c
>@@ -1700,6 +1700,9 @@ static void *get_partial(struct kmem_cache *s, gfp_t flags, int node,
> 	void *object;
>	int searchnode = (node == NUMA_NO_NODE) ? numa_node_id() : node;
>
>+	if (!node_present_pages(searchnode))
>+		searchnode = numa_mem_id();
>+
>	object = get_partial_node(s, get_node(s, searchnode), c, flags);
>	if (object || node != NUMA_NO_NODE)
>		return object;
>

The bug still can't be fixed w/ this patch. 

Regards,
Wanpeng Li 

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