Re: how to recycle Inact memory more aggressively?

On 2016-03-14 15:19, Ian Lepore wrote:
> On Sun, 2016-03-13 at 19:08 -0700, Adrian Chadd wrote:
>> On 13 March 2016 at 18:51, Mark Johnston <markj_at_freebsd.org> wrote:
>>> On Sun, Mar 13, 2016 at 06:33:46PM -0700, Adrian Chadd wrote:
>>>> Hi,
>>>>
>>>> I can reproduce this by doing a mkimage on a large destination
>>>> file
>>>> image. it looks like it causes all the desktop processes to get
>>>> paged
>>>> out whilst it's doing so, and then the whole UI freezes until it
>>>> catches up.
>>>
>>> mkimg(1) maps the destination file with MAP_NOSYNC, so if it's
>>> larger
>>> than RAM, I think it'll basically force the pagedaemon to write out
>>> the
>>> image as it tries to reclaim pages from the inactive queue. This
>>> can
>>> cause stalls if the pagedaemon blocks waiting for some I/O to
>>> complete.
>>> The user/alc/PQ_LAUNDRY branch helps alleviate this problem by
>>> using a
>>> different thread to launder dirty pages. I use mkimg on various
>>> desktop
>>> machines to build bhyve images and have noticed the problem you're
>>> describing; PQ_LAUNDRY helps quite a bit in that case. But I don't
>>> know
>>> why this would be a new problem.
>>>
>>
>> That's why I'm confused. I just know that it didn't used to cause the
>> whole UI to hang due to paging.
>>
> 
> I've been noticing this too.  This machine runs 10-stable and this use
> of the swap began happening recently when I updated from 10-stable
> around the 10.2 release time to 10-stable right about when the 10.3
> code freeze began.
> 
> In my case I have no zfs anything here.  I noticed the problem bigtime
> yesterday when rsync was syncing a ufs filesystem of about 500GB from
> one disk to another (probably 70-80 GB actually needed copying).  My
> desktop apps were noticibly unresponsive when I activated a window that
> had been idle for a while (like it would take a couple seconds for the
> app to begin responding).  I could see lots of swap In happening in top
> during this unresponsiveness, and noticible amounts of Out activity
> when nothing was happening except the rsync.
> 
> This is amd64, 12GB ram, 16GB swap, a tmpfs had about 400MB in it at
> the time.  Prior to the update around the 10.3 freeze, this machine
> would never touch the swap no matter what workload I threw at it (this
> rsync stuff happens every day, it's the usual workload).
> 

I'm not sure if it is the same problem, or port related.

On two systems without zfs but with many files e.g. svn servers I see now
from time to time they are running out of swap.

 kernel: swap_pager_getswapspace(9): failed
 kernel: swap_pager_getswapspace(16): failed
 ...

It also happened on one system during the nightly periodic tasks holding
only millions of backup files.

$ freebsd-version -ku
  10.2-RELEASE-p9
  10.2-RELEASE-p13