RE: format 2TB rbd device is too slow

[Ma, Jianpeng]

Ilya
 I modify kernel code. The patch like this:
[root@dev linux]# git diff
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index bc67a93..e4c4ea9 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -55,7 +55,7 @@
  * universally 512 bytes.  These symbols are just slightly more
  * meaningful than the bare numbers they represent.
  */
-#define        SECTOR_SHIFT    9
+#define        SECTOR_SHIFT    12
 #define        SECTOR_SIZE     (1ULL << SECTOR_SHIFT)

 /*
@@ -3811,6 +3811,7 @@ static int rbd_init_disk(struct rbd_device *rbd_dev)
        blk_queue_io_min(q, segment_size);
        blk_queue_io_opt(q, segment_size);

+       blk_queue_physical_block_size(q, SECTOR_SIZE);
        /* enable the discard support */
        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
        q->limits.discard_granularity = segment_size;

I don't know the exact why this can decrease the time.

For the -b of mkfs.xfs, I try for 65536. But it don't change any.


Thanks!

> -----Original Message-----
> From: Ilya Dryomov [mailto:idryo...@gmail.com]
> Sent: Friday, August 28, 2015 5:23 PM
> To: Ma, Jianpeng
> Cc: huang jun; Haomai Wang; ceph-devel
> Subject: Re: format 2TB rbd device is too slow
> 
> On Fri, Aug 28, 2015 at 10:36 AM, Ma, Jianpeng <jianpeng...@intel.com>
> wrote:
> > Hi Ilya,
> >    We can change sector size from 512 to 4096. This can reduce the count
> of write.
> > I did a simple test: for 900G, mkfs.xfs -f For default: 1m10s Physical
> > sector size = 4096:  0m10s.
> >
> > But if change sector size, we need rbd meta record this.
> 
> What exactly do you mean by changing the sector size?  xfs sector size or
> physical block size of the rbd device?  If the latter, meaning mkfs.xfs -s 
> size
> 4096, I fail to see how it can result in the above numbers.  If the former, 
> you
> have to patch the kernel and I fail to see how it can result in such an
> improvement too.  I probably didn't have enough coffee, please elaborate.
> 
> Thanks,
> 
>                 Ilya
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