svn commit: r331732 - head/sys/vm

[Tijl Coosemans]

On Sun, 1 Apr 2018 12:27:03 -0400 Mark Johnston <markj at FreeBSD.org> wrote:
> On Sun, Apr 01, 2018 at 05:20:21PM +0200, Tijl Coosemans wrote:
>> On Sat, 31 Mar 2018 18:54:32 -0400 Mark Johnston <markj at FreeBSD.org> wrote:  
>>> On Sat, Mar 31, 2018 at 08:21:18PM +0200, Tijl Coosemans wrote:  
>>>> On Thu, 29 Mar 2018 14:27:40 +0000 (UTC) Mark Johnston <markj at FreeBSD.org> wrote:    
>>>>> Author: markj
>>>>> Date: Thu Mar 29 14:27:40 2018
>>>>> New Revision: 331732
>>>>> URL: https://svnweb.freebsd.org/changeset/base/331732
>>>>> 
>>>>> Log:
>>>>>   Fix the background laundering mechanism after r329882.
>>>>>   
>>>>>   Rather than using the number of inactive queue scans as a metric for
>>>>>   how many clean pages are being freed by the page daemon, have the
>>>>>   page daemon keep a running counter of the number of pages it has freed,
>>>>>   and have the laundry thread use that when computing the background
>>>>>   laundering threshold.
>>>>> [...]    
>>>> 
>>>> I'm seeing big processes being killed with an "out of swap space" message
>>>> even though there's still plenty of swap available.  It seems to be fixed
>>>> by making this division round upwards:
>>>> 
>>>> 		if (target == 0 && ndirty * isqrt((nfreed +
>>>> 		    (vmd->vmd_free_target - vmd->vmd_free_min) - 1) /
>>>> 		    (vmd->vmd_free_target - vmd->vmd_free_min)) >= nclean) {
>>>> 
>>>> I don't know where this formula comes from, so I don't know if this
>>>> change is correct.    
>>> 
>>> Hm, that's somewhat surprising. This code shouldn't be executing in
>>> situations where the OOM kill logic is invoked (i.e., memory pressure
>>> plus a shortage of clean pages in the inactive queue).
>>> 
>>> How much RAM does the system have? Could you collect "sysctl vm" output
>>> around the time of an OOM kill?  
>> 
>> 1GiB RAM.  I've sampled sysctl vm every 5s from the moment the process
>> starts swapping until it is killed and uploaded that to
>> https://people.freebsd.org/~tijl/sysctl/  
> 
> Thank you. Now I agree with your change. Would you like to commit it?
> I can take care of it if you prefer.

Please go ahead.  You can probably write a better commit log.