bcache

Q:

1. 大block_size writethrough?
2. fio IOPS with writeback going -> 40k ~ 50k, initialized cache 50k, used cache 40k
3. after trigger_gc, cache_available don't get larger. --> pin: 0, mark: 1(dirty)

code flow:

• writeback:
  
  • request_write -> bch_writeback_add -> bch_writeback_queue -> refill_dirty -> read_dirty -> read_dirty_submit -> write_dirty -> write_dirty_finish
• write_dirty_finish:
  
  • bch_btree_insert
    
    • bch_btree_insert_recurse
      
      • __bkey_put(b->c, insert); // set pin to 0

pr_debug

enable pr_debug in bcache

1. mount -t debugfs /mnt/debugfs/ if debugfs is not mounted in /sys/kernel/debug/
2. echo 'file btree.c line 2349 +p' > /mnt/debugfs/dynamic_debug/control #show pr_debug in btree.c line 2349
3. echo 'module bcache +p' > /mnt/debugfs/dynamic_debug/control #show all pr_debug in bcache
4. "grep bch_btree_refill_keybuf /var/log/debug" or "dmesg|grep bch_btree_refill_keybuf"

screen to tmux

.tmux.conf:
unbind C-b
set -g prefix C-g
bind C-g last-window

set-option -g allow-rename off

-- hotkey of tmux --
ctrl-g l: last-windows
tmux attach: attach to existing session