+ linux-mm Summarizing the issue for linux-mm readers: If I read data from a storage device larger than my system's RAM, the system freezes once dd has read more data than available RAM. # dd if=/dev/sde of=/dev/null bs=1M & while true; do echo m > /proc/sysrq-trigger; echo; echo; sleep 1; done https://pastebin.ubuntu.com/p/HXzdqDZH4W/ A few seconds before the system hangs, Mem-Info shows: [ 90.986784] Node 0 active_anon:7060kB inactive_anon:13644kB active_file:0kB inactive_file:3797500kB [...] => 3797500kB is basically all of RAM. I tried to locate where "inactive_file" was being increased from, and saw two signatures: [ 255.606019] __mod_node_page_state | __pagevec_lru_add_fn | pagevec_lru_move_fn | __lru_cache_add | lru_cache_add | add_to_page_cache_lru | mpage_readpages | blkdev_readpages | read_pages | __do_page_cache_readahead | ondemand_readahead | page_cache_sync_readahead [ 255.637238] __mod_node_page_state | __pagevec_lru_add_fn | pagevec_lru_move_fn | __lru_cache_add | lru_cache_add | lru_cache_add_active_or_unevictable | __handle_mm_fault | handle_mm_fault | do_page_fault | do_translation_fault | do_mem_abort | el1_da Are these expected? NB: the system does not hang if I specify 'iflag=direct' to dd. According to the RCU watchdog: [ 108.466240] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 108.466420] rcu: 1-...0: (130 ticks this GP) idle=79e/1/0x4000000000000000 softirq=2393/2523 fqs=2626 [ 108.471436] rcu: (detected by 4, t=5252 jiffies, g=133, q=85) [ 108.480605] Task dump for CPU 1: [ 108.486483] kworker/1:1H R running task 0 680 2 0x0000002a [ 108.489977] Workqueue: kblockd blk_mq_run_work_fn [ 108.496908] Call trace: [ 108.501513] __switch_to+0x174/0x1e0 [ 108.503757] blk_mq_run_work_fn+0x28/0x40 [ 108.507589] process_one_work+0x208/0x480 [ 108.511486] worker_thread+0x48/0x460 [ 108.515480] kthread+0x124/0x130 [ 108.519123] ret_from_fork+0x10/0x1c Can anyone shed some light on what's going on? Regards.
