Re: mounting 4000 disks

[Andrew Morton]

Badari Pulavarty <[e-mail]> wrote:
>
> Hi,
> 
> I have been playing with testing 4000 disk support. (using 32bit dev_t).
> 
> I created 4000 disks using scsi_debug and mounted them.
> We consumed 84MB of low memory by just mouting 4000 filesystems.
> Out of 84MB lowmem 48MB is in slabs. 33 MB is used by buffers.

20 kbytes per disk+filesystem seems reasonable.

The "Buffers" will be the superblock (4k) and the group descriptor blocks
(256 bytes per gigabyte of disk).  These are pinned memory.

And the ext2 superblock got bigger in -mm due to the recent scalability
patches.

What is using the "size-8192" allocation there?  It could be the ext2 superblock
if you have NR_CPUS=32.