1) the platform is low memory platform having memory 64MB.
2) we are doing around 45MB TCP data transfer from PC to target using netcat utility .On Target , a process receives data over socket and writes the data to flash disk .
I think your network is faster than your disk ...
5) sometimes , we observed kernel memory getting exhausted as page allocation failure happens in kernel with the backtrace is printed below :
# [ 775.947949] nc.traditional: page allocation failure: order:0, mode:0x2080020(GFP_ATOMIC)
We're in the soft interrupt handler at this point, so we have very
few options for freeing memory; we can't wait for I/O to complete,
for example.
That said, this is a TCP connection. We could drop the packet silently
without such a noisy warning. Perhaps just collect statistics on how
many packets we dropped due to a low memory situation.
[ 775.956362] CPU: 0 PID: 1288 Comm: nc.traditional Tainted: G O 4.9.123-pic6-g31a13de-dirty #19
[ 775.966085] Hardware name: Generic R7S72100 (Flattened Device Tree)
[ 775.972501] [<c0109829>] (unwind_backtrace) from [<c010796f>] (show_stack+0xb/0xc)
[ 775.980118] [<c010796f>] (show_stack) from [<c0151de3>] (warn_alloc+0x89/0xba)
[ 775.987361] [<c0151de3>] (warn_alloc) from [<c0152043>] (__alloc_pages_nodemask+0x1eb/0x634)
[ 775.995790] [<c0152043>] (__alloc_pages_nodemask) from [<c0152523>] (__alloc_page_frag+0x39/0xde)
[ 776.004685] [<c0152523>] (__alloc_page_frag) from [<c03190f1>] (__netdev_alloc_skb+0x51/0xb0)
[ 776.013217] [<c03190f1>] (__netdev_alloc_skb) from [<c02c1b6f>] (sh_eth_poll+0xbf/0x3c0)
[ 776.021342] [<c02c1b6f>] (sh_eth_poll) from [<c031fd8f>] (net_rx_action+0x77/0x170)
[ 776.029051] [<c031fd8f>] (net_rx_action) from [<c011238f>] (__do_softirq+0x107/0x160)
[ 776.036896] [<c011238f>] (__do_softirq) from [<c0112589>] (irq_exit+0x5d/0x80)
[ 776.044165] [<c0112589>] (irq_exit) from [<c012f4db>] (__handle_domain_irq+0x57/0x8c)
[ 776.052007] [<c012f4db>] (__handle_domain_irq) from [<c01012e1>] (gic_handle_irq+0x31/0x48)
[ 776.060362] [<c01012e1>] (gic_handle_irq) from [<c0108025>] (__irq_svc+0x65/0xac)
[ 776.067835] Exception stack(0xc1cafd70 to 0xc1cafdb8)
[ 776.072876] fd60: 0002751c c1dec6a0 0000000c 521c3be5
[ 776.081042] fd80: 56feb08e f64823a6 ffb35f7b feab513d f9cb0643 0000056c c1caff10 ffffe000
[ 776.089204] fda0: b1f49160 c1cafdc4 c180c677 c0234ace 200e0033 ffffffff
[ 776.095816] [<c0108025>] (__irq_svc) from [<c0234ace>] (__copy_to_user_std+0x7e/0x430)
[ 776.103796] [<c0234ace>] (__copy_to_user_std) from [<c0241715>] (copy_page_to_iter+0x105/0x250)
[ 776.112503] [<c0241715>] (copy_page_to_iter) from [<c0319aeb>] (skb_copy_datagram_iter+0xa3/0x108)
[ 776.121469] [<c0319aeb>] (skb_copy_datagram_iter) from [<c03443a7>] (tcp_recvmsg+0x3ab/0x5f4)
[ 776.130045] [<c03443a7>] (tcp_recvmsg) from [<c035e249>] (inet_recvmsg+0x21/0x2c)
[ 776.137576] [<c035e249>] (inet_recvmsg) from [<c031009f>] (sock_read_iter+0x51/0x6e)
[ 776.145384] [<c031009f>] (sock_read_iter) from [<c017795d>] (__vfs_read+0x97/0xb0)
[ 776.152967] [<c017795d>] (__vfs_read) from [<c01781d9>] (vfs_read+0x51/0xb0)
[ 776.159983] [<c01781d9>] (vfs_read) from [<c0178aab>] (SyS_read+0x27/0x52)
[ 776.166837] [<c0178aab>] (SyS_read) from [<c0105261>] (ret_fast_syscall+0x1/0x54)
[ 776.174308] Mem-Info:
[ 776.176650] active_anon:2037 inactive_anon:23 isolated_anon:0
[ 776.176650] active_file:2636 inactive_file:7391 isolated_file:32
[ 776.176650] unevictable:0 dirty:1366 writeback:1281 unstable:0
Almost all the dirty pages are under writeback at this point.
[ 776.176650] slab_reclaimable:719 slab_unreclaimable:724
[ 776.176650] mapped:1990 shmem:26 pagetables:159 bounce:0
[ 776.176650] free:373 free_pcp:6 free_cma:0
We have 373 free pages, but refused to allocate one of them to GFP_ATOMIC?
I don't understand why that failed. We also didn't try to steal an
inactive_file or inactive_anon page, which seems like an obvious thing
we might want to do.
[ 776.209062] Node 0 active_anon:8148kB inactive_anon:92kB active_file:10544kB inactive_file:29564kB unevictable:0kB isolated(anon):0kB isolated(file):128kB mapped:7960kB dirty:5464kB writeback:5124kB shmem:104kB writeback_tmp:0kB unstable:0kB pages_scanned:0 all_unreclaimable? no
[ 776.233602] Normal free:1492kB min:964kB low:1204kB high:1444kB active_anon:8148kB inactive_anon:92kB active_file:10544kB inactive_file:29564kB unevictable:0kB writepending:10588kB present:65536kB managed:59304kB mlocked:0kB slab_reclaimable:2876kB slab_unreclaimable:2896kB kernel_stack:1152kB pagetables:636kB bounce:0kB free_pcp:24kB local_pcp:24kB free_cma:0kB
[ 776.265406] lowmem_reserve[]: 0 0
[ 776.268761] Normal: 7*4kB (H) 5*8kB (H) 7*16kB (H) 5*32kB (H) 6*64kB (H) 2*128kB (H) 2*256kB (H) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 1492kB
10071 total pagecache pages
[ 776.284124] 0 pages in swap cache
[ 776.287446] Swap cache stats: add 0, delete 0, find 0/0
[ 776.292645] Free swap = 0kB
[ 776.295532] Total swap = 0kB
[ 776.298421] 16384 pages RAM
[ 776.301224] 0 pages HighMem/MovableOnly
[ 776.305052] 1558 pages reserved