Re: [PATCH 0/5][RFC] Physical PCI slot objects

Andi Kleen
2007-11-14T14:35:37Z

On Wed, Nov 14, 2007 at 07:17:51AM -0700, Matthew Wilcox wrote:
> On Wed, Nov 14, 2007 at 02:07:56AM +0100, Andi Kleen wrote:
> > It's not only complexity. Each new sysfs entry costs memory.
> > Memory is not free. There should be always a good reason for those.
>
> It's not a lot of memory; it's one directory and a couple of files for
> each PCI slot in the system. Even huge systems have maybe 200 slots.
> In order for this to take up as much as one page of ram on a typical PC
> with six slots, this would have to consume 680 bytes per directory. I
> don't think sysfs is that inefficient (and if it is, maybe this feature
> is not where the problem is, given the 'power' directory per device, the
> 19 files per scsi device, the huge numbers of symlinks, etc).

It becomes much more when someone does a find /sys. dentries are
expensive. They eventually can get pruned again, but it's still
costly to do that.

-Andi