Linux aio_write is very slow in btrfs, almost reduced by 60% rate. Do someone know the reason?

Asked Jul 11 '13 at 08:50

Active Jul 11 '13 at 08:50

Viewed 318 times

Here is my code:

// init
int total;
struct aiocb aio;
bzero((char *)&aio, sizeof(struct aiocb));
aio.aio_buf = malloc(BUF_MAX1+1);
aio.aio_nbytes = BUF_MAX1;
aio.aio_fildes = write_file;
aio.aio_offset = 0;

int ret;
while (total <= 900008200){   // 858MB

    ret = aio_write(&aio);
    assert(ret >= 0);

    while ((ret = aio_error(&aio)) == EINPROGRESS);
    assert(ret == 0);

    int n;
    if ((n = aio_return(&aio)) > 0) {
        total += n;
        aio.aio_offset += n;
    } else {
        assert(0);
    }
}

When i run in ext4 filesystem, i got this results "total(900008200) time(12.63s)"

In btr filesystem the result is "total(900008200) time(27.42s)"

asked Jul 11 '13 at 08:50

Yifan Wang

Do you use recent kernel, like 3.10? – konrad.kruczynski Jul 12 '13 at 08:20
No, i use 3.5.0. And I can't upgrade kernel. 3.5.0 is stable version for my project. – Yifan Wang Jul 15 '13 at 05:55
Then you should at least run the same test on the newest kernel. There were a lot of efforts regarding BTRFS performance since 3.5. – konrad.kruczynski Jul 17 '13 at 07:59
thanks, so i have to drop the plan of aio in my project, but i will test the new kernel when have time :-) – Yifan Wang Jul 18 '13 at 01:15

Linux aio_write is very slow in btrfs, almost reduced by 60% rate. Do someone know the reason?

0 Answers0