linux-kernel - Re: rsdl:mouse freezing while doing git-gc

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Date:	Thu, 12 Apr 2007 14:10:05 +0200
From:	"Dmitry Adamushko" <dmitry.adamushko@...il.com>
To:	"surya.prabhakar@...ro.com" <surya.prabhakar@...ro.com>
Cc:	"Con Kolivas" <kernel@...ivas.org>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: rsdl:mouse freezing while doing git-gc

On 12/04/07, surya.prabhakar@...ro.com <surya.prabhakar@...ro.com> wrote:
> > [...]
> >
> > btw, it's sd-0.39, isn't?
> No! it is not. I have updated it to 2.6.21-rc5-sd-0.39.patch   and
> did the same tests.

It's nice-dependent. At least, that's something one would expect from
this design..

> PRI values s constantly changing while the git-gc is running. Is this
> expected behaviour?

Yep. Each nice level has a set of dynamic priorities which can be be
used by a task. After exhausting a time quota on a current level, the
task is moved to another (if there are no more -> "expired" array). So
the "PRI" field shows the current dynamic level.
The exceptions are SCHED_BATCH and Real-Time (FIFO and RR) tasks which
have different priority scheme.

/*
 * This contains a bitmap for each dynamic priority level with empty slots
 * for the valid priorities each different nice level can have. It allows
 * us to stagger the slots where differing priorities run in a way that
 * keeps latency differences between different nice levels at a minimum.
 * ie, where 0 means a slot for that priority, priority running from left to
 * right:
 * nice -20 0000000000000000000000000000000000000000
 * nice -10 1001000100100010001001000100010010001000
 * nice   0 0101010101010101010101010101010101010101
 * nice   5 1101011010110101101011010110101101011011
 * nice  10 0110111011011101110110111011101101110111
 * nice  15 0111110111111011111101111101111110111111
 * nice  19 1111111111111111111011111111111111111111

As you can see there is only a single possible level for nice 19
tasks, that's why your first results looked strange _but_ it might
have been due to the old version which lacks the prio_matrix (or it
was broken.. PRI == 0 for NICE 19 is very strabge indeed). So it's
good you have upgraded to the recent one.

I have made a small debugging extension that allows to monitor all the
priority levels (and how many times) being used by a given task
(configured via proc).. will test it later (don't have sd-enabled
kernel here). Just want to be sure that the "rules" are never broken.
Most likely Con did it already but as he is off-line we can't know.

>
> Did another test with hackbench and git-gc both at same priorities
> and captured the top output, in here all of them seem to have
> same priority..

Yep, this one looks good.

> thanks.
>
> surya.

-- 
Best regards,
Dmitry Adamushko
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