lkml.org 
[lkml]   [2020]   [Jan]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA
On Tue, Jan 21, 2020 at 02:29:49PM +0100, Peter Zijlstra wrote:
> On Mon, Dec 30, 2019 at 02:40:41PM -0500, Alex Kogan wrote:
>
> > +/*
> > + * Controls the threshold for the number of intra-node lock hand-offs before
> > + * the NUMA-aware variant of spinlock is forced to be passed to a thread on
> > + * another NUMA node. By default, the chosen value provides reasonable
> > + * long-term fairness without sacrificing performance compared to a lock
> > + * that does not have any fairness guarantees. The default setting can
> > + * be changed with the "numa_spinlock_threshold" boot option.
> > + */
> > +int intra_node_handoff_threshold __ro_after_init = 1 << 16;
>
> There is a distinct lack of quantitative data to back up that
> 'reasonable' claim there.
>
> Where is the table of inter-node latencies observed for the various
> values tested, and on what criteria is this number deemed reasonable?
>
> To me, 64k lock hold times seems like a giant number, entirely outside
> of reasonable.

Daniel, IIRC you just did a paper on constructing worst case latencies
from measuring pieces. Do you have data on average lock hold times?

\
 
 \ /
  Last update: 2020-01-21 14:51    [W:0.132 / U:0.356 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site