[ I'm CC'ing netdev. ]
On 24.8.2010 1.35, Stan Hoeppner wrote:
Pekka Enberg put forth on 8/23/2010 4:37 AM:
On 8/23/10 1:40 AM, Christoph Lameter wrote:
On Sun, 22 Aug 2010, Pekka Enberg wrote:
In Stan's case, it's a order-1 GFP_ATOMIC allocation but there are
only order-0 pages available. Mel, any recent page allocator fixes in
2.6.35 or 2.6.36-rc1 that Stan/Mikael should test?
This is the TCP slab? Best fix would be in the page allocator. However,
in this particular case the slub allocator would be able to fall back to
an order 0 allocation and still satisfy the request.
Looking at the stack trace of the oops, I think Stan has CONFIG_SLAB
which doesn't have order-0 fallback.
That is correct. The menuconfig help screen led me to believe the SLAB
allocator was the "safe" choice:
"CONFIG_SLAB:
The regular slab allocator that is established and known to work well in
all environments"
Should I be using SLUB instead? Any downsides to SLUB on an old and
slow (500 MHz) single core dual CPU box with<512MB RAM?
I don't think the problem here is SLAB so it shouldn't matter which one
you use. You might not see the problems with SLUB, though, because it
falls back to 0-order allocations.
Also, what is the impact of these oopses? Despite the entries in dmesg,
the system "seems" to be running ok. Or is this simply the calm before
the impending storm?
The page allocation failure in question is this:
kswapd0: page allocation failure. order:1, mode:0x20
Pid: 139, comm: kswapd0 Not tainted 2.6.34.1 #1
Call Trace:
[<c104b6b3>] ? __alloc_pages_nodemask+0x448/0x48a
[<c1062ffb>] ? cache_alloc_refill+0x22f/0x422
[<c11a9a73>] ? tcp_v4_send_check+0x6e/0xa4
[<c10632c3>] ? kmem_cache_alloc+0x41/0x6a
[<c11773a5>] ? sk_prot_alloc+0x19/0x55
[<c117744b>] ? sk_clone+0x16/0x1cc
[<c119a71d>] ? inet_csk_clone+0xf/0x80
[<c11ac0e3>] ? tcp_create_openreq_child+0x1a/0x3c8
[<c11aaf0a>] ? tcp_v4_syn_recv_sock+0x4b/0x151
[<c11abf9d>] ? tcp_check_req+0x209/0x335
[<c11aa892>] ? tcp_v4_do_rcv+0x8d/0x14d
[<c11aacd5>] ? tcp_v4_rcv+0x383/0x56d
[<c1193ba4>] ? ip_local_deliver+0x76/0xc0
[<c1193b10>] ? ip_rcv+0x3dc/0x3fa
[<c103655e>] ? ktime_get_real+0xf/0x2b
[<c117f8d3>] ? netif_receive_skb+0x219/0x234
[<c115ff46>] ? e100_poll+0x1d0/0x47e
[<c117fa98>] ? net_rx_action+0x58/0xf8
[<c102539c>] ? __do_softirq+0x78/0xe5
[<c102542c>] ? do_softirq+0x23/0x27
[<c1003955>] ? do_IRQ+0x7d/0x8e
[<c1002aa9>] ? common_interrupt+0x29/0x30
[<c1062870>] ? kmem_cache_free+0xbd/0xc5
[<c10fa7d1>] ? __xfs_inode_set_reclaim_tag+0x29/0x2f
[<c1075215>] ? destroy_inode+0x1c/0x2b
[<c10752ce>] ? dispose_list+0xaa/0xd0
[<c107548c>] ? shrink_icache_memory+0x198/0x1c5
[<c104f76b>] ? shrink_slab+0xda/0x12f
[<c104fc28>] ? kswapd+0x468/0x63b
[<c104dca3>] ? isolate_pages_global+0x0/0x1bc
[<c10304d6>] ? autoremove_wake_function+0x0/0x2d
[<c1018faf>] ? complete+0x28/0x36
[<c104f7c0>] ? kswapd+0x0/0x63b
[<c10301cd>] ? kthread+0x61/0x66
[<c103016c>] ? kthread+0x0/0x66
[<c1002ab6>] ? kernel_thread_helper+0x6/0x10
It looks to me as if tcp_create_openreq_child() is able to cope with the
situation so the warning could be harmless. If that's the case, we
should probably stick a __GFP_NOWARN there.
Pekka
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