Re: git: 4a864f624a70 - main - vm_pageout: Print a more accurate message to the console before an OOM kill [MFC in time for 13.1?]

On 2022-Jan-15, at 07:55, Mark Johnston <markj@FreeBSD.org> wrote:

> On Fri, Jan 14, 2022 at 09:38:56PM -0800, Mark Millard wrote:
>> Thanks. This will allow me to remove part of my personal additions
>> in this area --and my having to explain the misnomer when trying
>> to help someone analyze why they end up with OOM activity so they
>> can figure out what to do about it.
>> 
>> There seem to be two separate sources of VM_OOM_SWAPZ. Showing
>> my personal additions for them (just making them explicit in the
>> sequence of messages generated):
>> 
>> diff --git a/sys/vm/swap_pager.c b/sys/vm/swap_pager.c
>> index 01cf9233329f..280621ca51be 100644
>> --- a/sys/vm/swap_pager.c
>> +++ b/sys/vm/swap_pager.c
>> @@ -2091,6 +2091,7 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
>>                                    0, 1))
>>                                        printf("swap blk zone exhausted, "
>>                                            "increase kern.maxswzone\n");
>> +                               printf("swp_pager_meta_build: swap blk uma zone exhausted\n");
>>                                vm_pageout_oom(VM_OOM_SWAPZ);
>>                                pause("swzonxb", 10);
>>                        } else
>> @@ -2121,6 +2122,7 @@ swp_pager_meta_build(vm_object_t object, vm_pindex_t pindex, daddr_t swapblk)
>>                                    0, 1))
>>                                        printf("swap pctrie zone exhausted, "
>>                                            "increase kern.maxswzone\n");
>> +                               printf("swp_pager_meta_build: swap pctrie uma zone exhausted\n");
>>                                vm_pageout_oom(VM_OOM_SWAPZ);
>>                                pause("swzonxp", 10);
>>                        } else
>> 
>> Care to comment on the distinctions and why there are two
>> contexts classified as "out of swap space"? Would either
>> one show the swap space as (nearly?) all used in, say, top?
>> Or might one of them still end up looking like a misnomer
>> from just a top (or whatever) display?
> 
> Hmm, those cases should likely be changed from "out of swap space" to
> "failed to allocate swap metadata" or something like that.

The above does not seem to have happened yet in main [so: 14].

Will 13.1 get an MFC of 4a864f624a70 in time, possibly with the
above change also in place to fully avoid misnomer reporting
that misleads folks?

4a864f624a70 listed:

MFC after:	2 weeks

but it has been more than a month.

> . . .
> 

===
Mark Millard
marklmi at yahoo.com