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References: <164859751830.29473.5309689752169286816.stgit@noble.brown>
 <2923577.1648635976@warthog.procyon.org.uk> <164868916197.25542.11845352976146070176@noble.neil.brown.name>
In-Reply-To: <164868916197.25542.11845352976146070176@noble.neil.brown.name>
From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 19 Apr 2022 17:57:13 +0200
Message-ID: <CAMuHMdVJZmjM0yc=-iVi0y5ML6u8E4pG_RpLpwbZKu35Y9vOZQ@mail.gmail.com>
Subject: Re: [PATCH 00/10] MM changes to improve swap-over-NFS support
To:     NeilBrown <neilb@suse.de>
Cc:     David Howells <dhowells@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Christoph Hellwig <hch@infradead.org>,
        "open list:NFS, SUNRPC, AND..." <linux-nfs@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Neil,

On Thu, Mar 31, 2022 at 4:54 AM NeilBrown <neilb@suse.de> wrote:
> On Wed, 30 Mar 2022, David Howells wrote:
> > Do you have a branch with your patches on?
>
> http://git.neil.brown.name/?p=linux.git;a=shortlog;h=refs/heads/swap-nfs
>
> git://neil.brown.name/linux  branch swap-nfs
>
> Also  on https://github.com/neilbrown/linux.git same branch
>
> (it seems 1GB is no longer enough to run a git server for the kernel
>  effectively)
>
> This contains
>  - recent HEAD from Linus, which includes the NFS work
>  - the patches I sent to akpm
>  - the patch to switch NFS over to using the new swap_rw
>  - a SUNRPC patch to fix an easy crash.  But has always been there,
>     but recent changes to how kmalloc is called makes it much easier to
>     trigger.

Thanks for your series!

I gave this a try on Renesas RSK+RZA1 (RZ/A1H with 32 MiB of RAM)
and RZA2MEVB (RZ/A2M with 64 MiB of RAM) with a Debian nfsroot.
Seems to work, so
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>

However, I still managed to trigger memory allocation failures,
even on the RZ/A2, which I don't remember seeing last time I tried.

root@rza2mevb:~# free
              total        used        free      shared  buff/cache   available
Mem:          57428       12400       20024        1212       25004       40028
Swap:             0           0           0
root@rza2mevb:~# swapon /swap
Adding 1048572k swap on /swap.  Priority:-2 extents:1 across:1048572k
root@rza2mevb:~# apt update
Ign:1 http://ftp.be.debian.org/debian stretch InRelease
Get:2 http://security.debian.org stretch/updates InRelease [53.0 kB]
Hit:3 http://ftp.be.debian.org/debian stretch Release
Get:5 http://security.debian.org stretch/updates/main armhf Packages [738 kB]
Get:6 http://security.debian.org stretch/updates/main Translation-en [356 kB]
Fetched 1,147 kB in 12s (89.5 kB/s)
apt: page allocation failure: order:0,
mode:0x40cc0(GFP_KERNEL|__GFP_COMP), nodemask=(null)
CPU: 0 PID: 455 Comm: apt Not tainted
5.18.0-rc3-rza2mevb-00734-g98e2a6b7a591 #186
Hardware name: Generic R7S9210 (Flattened Device Tree)
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from warn_alloc+0xa0/0x150
 warn_alloc from __alloc_pages+0x3a0/0x8c0
 __alloc_pages from ____cache_alloc+0x194/0x734
 ____cache_alloc from kmem_cache_alloc+0x60/0xd0
 kmem_cache_alloc from nfs_writehdr_alloc+0x28/0x70
 nfs_writehdr_alloc from nfs_pgio_header_alloc+0x10/0x28
 nfs_pgio_header_alloc from nfs_generic_pg_pgios+0x14/0xa8
 nfs_generic_pg_pgios from nfs_pageio_doio+0x2c/0x4c
 nfs_pageio_doio from __nfs_pageio_add_request+0x34c/0x3c8
 __nfs_pageio_add_request from nfs_pageio_add_request_mirror+0x18/0x44
 nfs_pageio_add_request_mirror from nfs_pageio_add_request+0x1b8/0x1c8
 nfs_pageio_add_request from nfs_direct_write_schedule_iovec+0x208/0x28c
 nfs_direct_write_schedule_iovec from nfs_file_direct_write+0x128/0x21c
 nfs_file_direct_write from nfs_swap_rw+0x24/0x28
 nfs_swap_rw from swap_write_unplug+0x54/0x94
 swap_write_unplug from __swap_writepage+0x10c/0x20c
 __swap_writepage from shrink_page_list+0x86c/0xabc
 shrink_page_list from shrink_inactive_list+0xfc/0x2b0
 shrink_inactive_list from shrink_node+0x598/0x80c
 shrink_node from try_to_free_pages+0x2bc/0x3e8
 try_to_free_pages from __alloc_pages+0x55c/0x8c0
 __alloc_pages from __filemap_get_folio+0x1b4/0x260
 __filemap_get_folio from pagecache_get_page+0x10/0x68
 pagecache_get_page from nfs_write_begin+0x30/0x148
 nfs_write_begin from generic_perform_write+0xa4/0x1b8
 generic_perform_write from nfs_file_write+0xf0/0x2a4
 nfs_file_write from vfs_write+0x140/0x19c
 vfs_write from ksys_write+0x74/0xc8
 ksys_write from ret_fast_syscall+0x0/0x54
Exception stack(0xc4c1dfa8 to 0xc4c1dff0)
dfa0:                   b6ec4025 00000000 00000004 b1d0e000 019f12ac befee52c
dfc0: b6ec4025 00000000 019f12ac 00000004 019f12ac b1d0e000 befee52c befee7ac
dfe0: 00000000 befee4d4 b6ec0b43 b6cb1cf6
Mem-Info:
active_anon:1772 inactive_anon:7471 isolated_anon:64
 active_file:679 inactive_file:392 isolated_file:0
 unevictable:0 dirty:0 writeback:2891
 slab_reclaimable:417 slab_unreclaimable:2863
 mapped:32 shmem:52 pagetables:107 bounce:0
 kernel_misc_reclaimable:0
 free:0 free_pcp:6 free_cma:0
Node 0 active_anon:7088kB inactive_anon:29884kB active_file:2716kB
inactive_file:1568kB unevictable:0kB isolated(anon):256kB
isolated(file):0kB mapped:128kB dirty:0kB writeback:11564kB
shmem:208kB writeback_tmp:0kB kernel_stack:408kB pagetables:428kB
all_unreclaimable? no
Normal free:0kB boost:4096kB min:5044kB low:5280kB high:5516kB
reserved_highatomic:0KB active_anon:7088kB inactive_anon:29884kB
active_file:2716kB inactive_file:1568kB unevictable:0kB
writepending:10296kB present:65536kB managed:57428kB mlocked:0kB
bounce:0kB free_pcp:24kB local_pcp:24kB free_cma:0kB
lowmem_reserve[]: 0 0
Normal: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB
0*1024kB 0*2048kB 0*4096kB = 0kB
7385 total pagecache pages
6262 pages in swap cache
Swap cache stats: add 6787, delete 525, find 58/74
Free swap  = 1021476kB
Total swap = 1048572kB
16384 pages RAM
0 pages HighMem/MovableOnly
2027 pages reserved
Write error -12 on dio swapfile (27660288)
Write error -12 on dio swapfile (29679616)
Write error -12 on dio swapfile (8572928)
Write error 0 on dio swapfile (8441856)
Write error 0 on dio swapfile (8704000)
Write error -12 on dio swapfile (8966144)
Write error -12 on dio swapfile (9097216)
Write error 0 on dio swapfile (8835072)
Write error 0 on dio swapfile (9228288)
Write error 0 on dio swapfile (9359360)
sio_write_complete: 2731 callbacks suppressed
Write error 0 on dio swapfile (34705408)
Write error 0 on dio swapfile (23470080)
Write error 0 on dio swapfile (23601152)
Write error 0 on dio swapfile (23732224)
Write error 0 on dio swapfile (4202496)
Write error 0 on dio swapfile (4304896)
Write error 0 on dio swapfile (4435968)
Write error 0 on dio swapfile (4567040)
Write error 0 on dio swapfile (4698112)
Write error 0 on dio swapfile (4829184)
warn_alloc: 125849 callbacks suppressed
kworker/u2:7: page allocation failure: order:0,
mode:0x60c40(GFP_NOFS|__GFP_COMP|__GFP_MEMALLOC), nodemask=(null)
CPU: 0 PID: 457 Comm: kworker/u2:7 Not tainted
5.18.0-rc3-rza2mevb-00734-g98e2a6b7a591 #186
Hardware name: Generic R7S9210 (Flattened Device Tree)
Workqueue: rpciod rpc_async_schedule
 unwind_backtrace from show_stack+0x10/0x14
 show_stack from warn_alloc+0xa0/0x150
 warn_alloc from __alloc_pages+0x3a0/0x8c0
 __alloc_pages from ____cache_alloc+0x194/0x734
 ____cache_alloc from __kmalloc_track_caller+0x74/0xf0
 __kmalloc_track_caller from kmalloc_reserve.constprop.0+0x4c/0x60
 kmalloc_reserve.constprop.0 from __alloc_skb+0x88/0x154
 __alloc_skb from tcp_stream_alloc_skb+0x68/0x13c
 tcp_stream_alloc_skb from tcp_sendmsg_locked+0x4b8/0xabc
 tcp_sendmsg_locked from tcp_sendmsg+0x24/0x38
 tcp_sendmsg from sock_sendmsg_nosec+0x14/0x24
 sock_sendmsg_nosec from xprt_sock_sendmsg+0x1d8/0x244
 xprt_sock_sendmsg from xs_tcp_send_request+0x11c/0x20c
 xs_tcp_send_request from xprt_transmit+0x84/0x234
 xprt_transmit from call_transmit+0x6c/0x7c
 call_transmit from __rpc_execute+0xe4/0x2f0
 __rpc_execute from rpc_async_schedule+0x18/0x24
 rpc_async_schedule from process_one_work+0x170/0x210
 process_one_work from worker_thread+0x204/0x2a4
 worker_thread from kthread+0xb0/0xbc
 kthread from ret_from_fork+0x14/0x2c
Exception stack(0xc4e0dfb0 to 0xc4e0dff8)
dfa0:                                     00000000 00000000 00000000 00000000
dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
Mem-Info:
active_anon:2703 inactive_anon:6291 isolated_anon:209
 active_file:541 inactive_file:530 isolated_file:0
 unevictable:0 dirty:0 writeback:3781
 slab_reclaimable:391 slab_unreclaimable:2993
 mapped:0 shmem:0 pagetables:107 bounce:0
 kernel_misc_reclaimable:0
 free:0 free_pcp:26 free_cma:0
Node 0 active_anon:10812kB inactive_anon:25164kB active_file:2164kB
inactive_file:2120kB unevictable:0kB isolated(anon):836kB
isolated(file):0kB mapped:0kB dirty:0kB writeback:15124kB shmem:0kB
writeback_tmp:0kB kernel_stack:408kB pagetables:428kB
all_unreclaimable? yes
Normal free:0kB boost:0kB min:948kB low:1184kB high:1420kB
reserved_highatomic:0KB active_anon:10812kB inactive_anon:25164kB
active_file:2164kB inactive_file:2120kB unevictable:0kB
writepending:13284kB present:65536kB managed:57428kB mlocked:0kB
bounce:0kB free_pcp:104kB local_pcp:104kB free_cma:0kB
lowmem_reserve[]: 0 0
Normal: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB
0*1024kB 0*2048kB 0*4096kB = 0kB
10274 total pagecache pages
9203 pages in swap cache
Swap cache stats: add 9834, delete 631, find 61/77
Free swap  = 1009180kB
Total swap = 1048572kB
16384 pages RAM
0 pages HighMem/MovableOnly
2027 pages reserved
sio_write_complete: 29066 callbacks suppressed
...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds