lkml.org 
[lkml]   [2016]   [Jul]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 1/7] lib/dlock-list: Distributed and lock-protected lists
Hello, Jan.

On Thu, Jul 14, 2016 at 04:35:47PM +0200, Jan Kara wrote:
> > > The current use case only need to use the regular lock functions. You are
> > > right that future use cases may require an irqsafe version of locks. I can
> > > either modify the code now to allow lock type selection at init time, for
> > > example, or defer it as a future enhancement when the need arises. What do
> > > you think?
> >
> > The bulk of performance gain of dlist would come from being per-cpu
> > and I don't think it's likely that we'd see any noticeable difference
> > between irq and preempt safe operations. Given that what's being
> > implemented is really low level operations, I'd suggest going with
> > irqsafe from the get-go.
>
> I'm not sure here. i_sb_list for which percpu lists will be used is bashed
> pretty heavily under some workloads and the cost of additional interrupt
> disabling & enabling may be visible under those loads. Probably not in the
> cases where you get a boost from percpu lists but if the workload is mostly
> single-threaded, additional cpu cost may be measurable. So IMO we should
> check whether a load which creates tons of empty inodes in tmpfs from a
> single process doesn't regress with this change.

Sure, if it actually matters, we can always create separate preempt /
irq variants.

Thanks.

--
tejun

\
 
 \ /
  Last update: 2016-07-14 17:21    [W:0.063 / U:0.744 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site