lkml.org 
[lkml]   [2019]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] psi:fix divide by zero in psi_update_stats
On Tue, Nov 12, 2019 at 10:41:46AM -0500, Johannes Weiner wrote:
> On Fri, Nov 08, 2019 at 03:33:24PM +0800, tim wrote:
> > In psi_update_stats, it is possible that period has value like
> > 0xXXXXXXXX00000000 where the lower 32 bit is 0, then it calls div_u64 which
> > truncates u64 period to u32, results in zero divisor.
> > Use div64_u64() instead of div_u64() if the divisor is u64 to avoid
> > truncation to 32-bit on 64-bit platforms.
> >
> > Signed-off-by: xiejingfeng <xiejingfeng@linux.alibaba.com>
>
> This is legit. When we stop the periodic averaging worker due to an
> idle CPU, the period after restart can be much longer than the ~4 sec
> in the lower 32 bits. See the missed_periods logic in update_averages.

Argh, that's not right. Of course I notice right after hitting send.

missed_periods are subtracted out of the difference between now and
the last update, so period should be not much bigger than 2s.

Something else is going on here.

\
 
 \ /
  Last update: 2019-11-12 16:49    [W:0.075 / U:2.124 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site