confuse about the alignment about directio HOT 6 CLOSED

I would guess you are running on macOS - this doesn't need any alignment.

What OS are you using?

from directio.

@ncw I was test on linux kernel version 5.8.15
the test code is as simple as

package main

import (
  "fmt"
  "github.com/ncw/directio"
)


func main() {
  block := directio.AlignedBlock(3000)
  fmt.Printf("block is %d\n", len(block))
}

and the result is

[vagrant@testbox directio-test]$ go run main.go
block is 3000

which I expect to see is 4096

from directio.

I see your confusion now. directio.AlignedBlock will return only the size that you asked for but it is guaranteed to be aligned to a page boundary.

package main

import (
	"fmt"

	"github.com/ncw/directio"
)

func main() {
	block := directio.AlignedBlock(3000)
	fmt.Printf("block is %d\n", len(block))
	fmt.Printf("block is at %p", &block[0])
}

https://go.dev/play/p/mcHTD5COgBi

Prints

block is 3000
block is at 0xc00007e000

so the block is clearly aligned.

I'll close this now as I think the question is answered.

from directio.

thanks for the clarify

from directio.

No probs!

I'll close this now.

from directio.

in this test code, if its ok when the block which size is 3000 is write to a file in driect IO?

from directio.