mmap中的read ahead

https://github.com/elastic/elasticsearch/issues/27748

上面这个issue提到

The bottleneck came from the memory management read ahead which is different from the block device read ahead.

The memory management read ahead is only used for mapped files and the block device read ahead for all read operations on storage devices whether using niofs or mmapfs.

In fact, the 2MB read ahead limit I observed in my tests seems to be hard coded in the kernel: https://github.com/torvalds/linux/blob/master/mm/readahead.c#L236

mmap有他自己的readahead, (感觉有些多此一举, 我知道一定是我理解不深刻), 可以用 madvise 避免

嘿嘿嘿

我要是个富二代就好了, 算了算了, 我还是要上进的…

ticker会不会堆积

package main

import (
	"flag"
	"log"
	"sync"
	"time"
)

func main() {
	flag.Parse()
	log.Println("start")
	ticker := time.NewTicker(time.Second * 3)
	i := 3
	lock := &sync.Mutex{}
	for range ticker.C {
		lock.Lock()
		log.Printf("sleep %d second", i)
		time.Sleep(time.Second * time.Duration(i))
		i = (i + 1) % 6
		lock.Unlock()
	}
}

2020/02/22 19:14:03 start
2020/02/22 19:14:06 sleep 3 second
2020/02/22 19:14:09 sleep 4 second
2020/02/22 19:14:13 sleep 5 second
2020/02/22 19:14:18 sleep 0 second
2020/02/22 19:14:21 sleep 1 second
2020/02/22 19:14:24 sleep 2 second
2020/02/22 19:14:27 sleep 3 second
2020/02/22 19:14:30 sleep 4 second
2020/02/22 19:14:34 sleep 5 second

夏天结束了

日语里「夏天结束了」其实和「今晚月色真美」一样，是有隐晦暗示的。代表着某天突然感知到河岸的风带来凉意，爱慕的心绪不了了之，没牵到的手，未送出的信，青春潦草收场后关上了门。就像睡了漫长的午觉醒来，穿衣洗漱准备去学校，找了半天却找不到课本和双肩包，才恍惚想起自己在多年前明明没有做好准备，就被推搡着长大成人。来不及跟夏天挥手告别的仓促人生，年轻时也对世间万物充满期待，眨眼间就落入了平庸之海。
夏が終わった。

40安天命?

我是一直都觉得感情的事难以控制, 可能突然之间就不喜欢了. 接受自己这样, 也接受别人这样. 40可安天命, 但行好事, 莫问西东?

依赖

说好的不依赖尼?

烦

昨天是在梦游吗?! 现在心里好烦好纠结.

mdadm lvm

mdadm先把物理盘做成Raid, 然后LVM把Raid做成pv.

想看书

每次到书店, 都想”我要看书看书看书, 每天大把时间去看书, 我要看这本, 这本, 还有这本也要看”, 可是出来后不久就没这么想了..

123456

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