Messages in this thread | | | Subject | Re: bdi_min_ratio never shrinks, ultimately preventing valid setting of min_ratio | From | Peter Zijlstra <> | Date | Thu, 02 Jun 2011 13:43:31 +0200 |
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It really helps if you CC the relevant people.
On Tue, 2011-05-31 at 19:28 -0500, lkml@pengaru.com wrote: > mm/page-writeback.c > There is a static global bdi_min_ratio used for policing the setting of > per-bdi min_ratio's, to ensure the sum doesn't cross 100. > > There is no place in this listing where the value is decremented by the > respective bdi's min_ratio when a bdi is torn down.
There is, adding a negative number is equal to a subtraction.
min_ratio -= bdi->min_ratio; if (bdi_min_ratio + min_ratio < 100) { bdi_min_ratio += min_ratio; bdi->min_ratio += min_ratio; }
is the relevant piece, note that bdi->min_ratio is the current setting, this makes min_ratio the difference between the new and old setting, and adding this to both bdi_min_ratio (the global sum) and bdi->min_ratio dtrt regardless if the new value is larger or smaller than the old value.
> This looks like a bug > to me, and I have a situation where I'm unable to set a min_ratio to 1 > where the sum of /sys/class/bdi/*/min_ratio does not add up to 100, which > is what triggered this investigation.
Which of the two -EINVAL cases is triggered?
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