lkml.org 
[lkml]   [2015]   [Nov]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] sched: prevent getting too much vruntime
On Wed, Nov 11, 2015 at 05:50:27PM +0900, byungchul.park@lge.com wrote:

I've not actually read anything; my brain isn't working right today.

> +static inline void vruntime_unnormalize(struct cfs_rq *cfs_rq, struct sched_entity *se)
> +{
> + se->vruntime += cfs_rq->min_vruntime;
> + if (unlikely((s64)se->vruntime < 0))
> + se->vruntime = 0;
> +}

But this is broken. This simply _cannot_ be right.

vruntime very much needs to wrap in u64 space. While regular time in ns
takes some 584 year to wrap, vruntime is scaled. The fastest vruntime is
2/1024 or 512 times faster than normal time. Making it take just over a
year to wrap around. This will happen.




\
 
 \ /
  Last update: 2015-11-11 10:41    [W:0.046 / U:0.568 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site