linux network configurations
configs: diry_page config https://lonesysadmin.net/2013/12/22/better-linux-disk-caching-performance-vm-dirty_ratio/
common tunning techniques: https://www.percona.com/blog/2016/08/12/tuning-linux-for-mongodb/
tools: hdparam : test read performance
proc: /sys/block/sda/queue/scheduler : disk task scheduler
/sys/block/sda/queue/read_ahead_kb : read ahead
/proc/sys/vm/nr_pdflush_threads : number of pdflush thread running(not configurable now https://patchwork.kernel.org/patch/9983043/)
/proc/sys/vm/dirty_expire_centisecs : if data has stayed longer than this, flush it
/proc/sys/vm/dirty_writeback_centisecs : pdflush running interval. it can be disabled
/proc/sys/vm/dirty_background_ratio : pdflush kicks in to flush out dirty pages
/proc/sys/vm/dirty_ratio : application write blocks if dirty memory ratio reach this limit
greate resources:
- hdparam -t(cached:no disk access) and -T(buffered: just disk access) : https://www.unix.com/unix-for-dummies-questions-and-answers/163209-difference-between-buffered-disk-reads-cached-reads.html
- over commit : https://www.kernel.org/doc/Documentation/vm/overcommit-accounting
- linux config : https://www.kernel.org/doc/Documentation/sysctl/vm.txt