-----Original Message-----
From: Matthew Wilcox [mailto:wi...@infradead.org]
Sent: Saturday, June 1, 2019 1:01 AM
To: Nagal, Amit UTC CCS <amit.na...@utc.com>
Cc: linux-kernel@vger.kernel.org; linux...@kvack.org; CHAWLA, RITU UTC CCS
<ritu.cha...@utc.com>; net...@vger.kernel.org
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.
I will collect statistics for it .
> [ 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
