lkml.org 
[lkml]   [2015]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 26/51] writeback: let balance_dirty_pages() work on the matching cgroup bdi_writeback
Hello, Jan.

On Tue, Jun 30, 2015 at 04:31:00PM +0200, Jan Kara wrote:
...
> > + if (inode_cgwb_enabled(inode))
> > + wb = wb_get_create_current(bdi, GFP_KERNEL);
> > + if (!wb)
> > + wb = &bdi->wb;
> > +
>
> So this effectively adds a radix tree lookup (of wb belonging to memcg) for
> every set_page_dirty() call. That seems relatively costly to me. And all

Hmmm... idk, radix tree lookups should be cheap especially when
shallow and set_page_dirty(). It's a glorified array indexing. If
not, we should really be improving radix tree implementation. That
said,

> that just to check wb->dirty_exceeded. Cannot we just use inode_to_wb()
> instead? I understand results may be different if multiple memcgs share an
> inode and that's the reason why you use wb_get_create_current(), right?
> But for dirty_exceeded check it may be good enough?

Yeah, that probably should work. I'll think more about it.

Thanks.

--
tejun


\
 
 \ /
  Last update: 2015-07-02 03:41    [W:0.117 / U:0.636 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site