-----Original Message----- From: Nagal, Amit UTC CCS Sent: Monday, June 3, 2019 11:08 AM To: 'Matthew Wilcox' <willy@xxxxxxxxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; CHAWLA, RITU UTC CCS <RITU.CHAWLA@xxxxxxx>; netdev@xxxxxxxxxxxxxxx; Netter, Christian M UTC CCS <christian.Netter@xxxxxxxxxx> Subject: RE: [External] Re: linux kernel page allocation failure and tuning of page cache -----Original Message----- From: Matthew Wilcox [mailto:willy@xxxxxxxxxxxxx] Sent: Saturday, June 1, 2019 1:01 AM To: Nagal, Amit UTC CCS <Amit.Nagal@xxxxxxx> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx; CHAWLA, RITU UTC CCS <RITU.CHAWLA@xxxxxxx>; netdev@xxxxxxxxxxxxxxx Subject: [External] Re: linux kernel page allocation failure and tuning of page cache > 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 ... >Ok . I need to check it . But how does this affect page reclaim procedure . > 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. total used free shared buffers cached Mem: 57 56 1 0 0 20 -/+ buffers/cache: 35 22 Swap: 0 0 0 eth0 Link encap:Ethernet HWaddr D6:8C:FD:9D:35:AC inet addr:169.254.1.1 Bcast:0.0.0.0 Mask:255.255.255.0 inet6 addr: fe80::d48c:fdff:fe9d:35ac/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:8466 errors:1 dropped:0 overruns:3 frame:5 TX packets:1085 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:12230677 (11.6 MiB) TX bytes:107425 (104.9 KiB) Interrupt:77 Base address:0x3000 Not too many packet drops seem to happen . > [ 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. >Yes that's where I am concerned . we do not have swap device so I am assuming perhaps inactive_anon pages are not stolen , but inactive_file pages could have been used . > [ 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
