I was copying files to a Pi via the samba share on the device itself from another Linux machine and it worked fine until I reached a large file (a PlayStation disc BIN file) which then slowed to a crawl and threw an error. It looks like Samba tries to use too much RAM on the Batocera side and is killed due to the whole machine going OOM (even with EmulationStation shut down).
[31538.677555] smbd invoked oom-killer: gfp_mask=0x1c200ca(GFP_HIGHUSER_MOVABLE|__GFP_WRITE), nodemask=(null), order=0, oom_score_adj=0
[31538.677570] smbd cpuset=/ mems_allowed=0
[31538.677585] CPU: 1 PID: 3742 Comm: smbd Tainted: G C 4.14.39-v7 #1
[31538.677587] Hardware name: BCM2835
[31538.677610] [<80110258>] (unwind_backtrace) from [<8010c41c>] (show_stack+0x20/0x24)
[31538.677622] [<8010c41c>] (show_stack) from [<80793560>] (dump_stack+0xcc/0x110)
[31538.677632] [<80793560>] (dump_stack) from [<80225d5c>] (dump_header+0xb0/0x234)
[31538.677641] [<80225d5c>] (dump_header) from [<8022545c>] (oom_kill_process+0x32c/0x5a8)
[31538.677649] [<8022545c>] (oom_kill_process) from [<80225b18>] (out_of_memory+0x1f0/0x31c)
[31538.677657] [<80225b18>] (out_of_memory) from [<8022b3fc>] (__alloc_pages_nodemask+0x1068/0x1134)
[31538.677666] [<8022b3fc>] (__alloc_pages_nodemask) from [<8021f33c>] (pagecache_get_page+0xd0/0x2e4)
[31538.677673] [<8021f33c>] (pagecache_get_page) from [<80220160>] (grab_cache_page_write_begin+0x28/0x3c)
[31538.677682] [<80220160>] (grab_cache_page_write_begin) from [<8033e1a8>] (ext4_da_write_begin+0xa8/0x41c)
[31538.677689] [<8033e1a8>] (ext4_da_write_begin) from [<802202dc>] (generic_perform_write+0xb0/0x1ac)
[31538.677695] [<802202dc>] (generic_perform_write) from [<80222b3c>] (__generic_file_write_iter+0x11c/0x1d0)
[31538.677704] [<80222b3c>] (__generic_file_write_iter) from [<80329dd8>] (ext4_file_write_iter+0xd4/0x440)
[31538.677712] [<80329dd8>] (ext4_file_write_iter) from [<8028c624>] (__vfs_write+0xe0/0x130)
[31538.677720] [<8028c624>] (__vfs_write) from [<8028c838>] (vfs_write+0xb4/0x1c0)
[31538.677726] [<8028c838>] (vfs_write) from [<8028cbe8>] (SyS_pwrite64+0x84/0x9c)
[31538.677734] [<8028cbe8>] (SyS_pwrite64) from [<80108220>] (ret_fast_syscall+0x0/0x28)
[31538.677739] Mem-Info:
[31538.677750] active_anon:115623 inactive_anon:902 isolated_anon:0
[31538.677750] active_file:376 inactive_file:386 isolated_file:0
[31538.677750] unevictable:0 dirty:17 writeback:689 unstable:0
[31538.677750] slab_reclaimable:1829 slab_unreclaimable:2755
[31538.677750] mapped:1441 shmem:2334 pagetables:596 bounce:0
[31538.677750] free:951 free_pcp:353 free_cma:0
[31538.677760] Node 0 active_anon:462492kB inactive_anon:3608kB active_file:1504kB inactive_file:1544kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:5764kB dirty:68kB writeback:2756kB shmem:9336kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
[31538.677771] Normal free:3804kB min:2820kB low:3524kB high:4228kB active_anon:462492kB inactive_anon:3608kB active_file:1668kB inactive_file:1472kB unevictable:0kB writepending:2672kB present:524288kB managed:507304kB mlocked:0kB kernel_stack:1688kB pagetables:2384kB bounce:0kB free_pcp:1412kB local_pcp:572kB free_cma:0kB
[31538.677773] lowmem_reserve[]: 0 0
[31538.677779] Normal: 15*4kB (H) 21*8kB (H) 21*16kB (H) 19*32kB (H) 13*64kB (H) 6*128kB (H) 4*256kB (H) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3796kB
[31538.677814] 3122 total pagecache pages
[31538.677818] 0 pages in swap cache
[31538.677820] Swap cache stats: add 0, delete 0, find 0/0
[31538.677822] Free swap = 0kB
[31538.677824] Total swap = 0kB
[31538.677827] 131072 pages RAM
[31538.677829] 0 pages HighMem/MovableOnly
[31538.677831] 4246 pages reserved
[31538.677833] 2048 pages cma reserved
[31538.677835] [ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name
[31538.677852] [ 117] 0 117 629 16 6 0 0 0 syslogd
[31538.677858] [ 120] 0 120 629 23 4 0 0 0 klogd
[31538.677862] [ 141] 0 141 733 35 5 0 0 0 dbus-daemon
[31538.677867] [ 147] 0 147 1152 138 5 0 0 -1000 udevd
[31538.677876] [ 205] 1001 205 766 88 6 0 0 0 dbus-daemon
[31538.677881] [ 218] 0 218 1263 107 7 0 0 0 connmand
[31538.677887] [ 221] 0 221 432 20 4 0 0 0 thd
[31538.677892] [ 315] 0 315 1275 88 7 0 0 0 wpa_supplicant
[31538.677898] [ 919] 0 919 1267 66 7 0 0 0 lircd
[31538.677905] [ 1002] 0 1002 848 46 5 0 0 0 S31emulationsta
[31538.677910] [ 1004] 0 1004 39958 7897 50 0 0 0 emulationstatio
[31538.677916] [ 1011] 0 1011 1316 118 8 0 0 0 bluetoothd
[31538.677921] [ 1012] 0 1012 848 46 5 0 0 0 S32bluetooth
[31538.677926] [ 1045] 0 1045 2034 124 8 0 0 0 ntpd
[31538.677931] [ 1051] 1000 1051 884 66 5 0 0 0 avahi-daemon
[31538.677936] [ 1056] 0 1056 559 26 4 0 0 0 dropbear
[31538.677941] [ 1067] 0 1067 8694 713 22 0 0 0 smbd
[31538.677946] [ 1070] 0 1070 7745 373 19 0 0 0 smbd-notifyd
[31538.677951] [ 1071] 0 1071 7746 372 18 0 0 0 cleanupd
[31538.677956] [ 1072] 0 1072 8691 427 20 0 0 0 lpqd
[31538.677961] [ 1073] 0 1073 5311 298 15 0 0 0 nmbd
[31538.677965] [ 1094] 0 1094 629 9 5 0 0 0 getty
[31538.677970] [ 1095] 0 1095 629 9 5 0 0 0 getty
[31538.677975] [ 1096] 0 1096 1111 130 7 0 0 0 alsamixer
[31538.677980] [ 1105] 0 1105 454 30 5 0 0 0 hciattach
[31538.677985] [ 1108] 0 1108 3726 909 11 0 0 0 btDaemon
[31538.677990] [ 3350] 0 3350 319488 104978 329 0 0 0 smbd
[31538.677995] Out of memory: Kill process 3350 (smbd) score 805 or sacrifice child
[31538.678169] Killed process 3350 (smbd) total-vm:1277952kB, anon-rss:414352kB, file-rss:8kB, shmem-rss:5552kB
[31538.769509] oom_reaper: reaped process 3350 (smbd), now anon-rss:0kB, file-rss:0kB, shmem-rss:5552kB
Not sure if there's an easy way to tell Samba to use less RAM, or whether this is just going to be an unfixable issue due to the Pi's lack of RAM (the Odroid-XU4 had no such issues, it was also exponentially faster copying the files too).
