Those are also constantly running on this system (30G free mem):
101 root 20 0 0 0 0 S 12,9 0,0 40:38.45
[kswapd0]
89 root 39 19 0 0 0 S 11,6 0,0 38:58.84
[khugepaged]
# cat /proc/pagetypeinfo
Page block order: 9
Pages per block: 512
Free pages count per migrate type at order 0 1 2 3
4 5 6 7 8 9 10
Node 0, zone DMA, type Unmovable 0 0 0 1
2 1 1 0 1 0 0
Node 0, zone DMA, type Movable 0 0 0 0
0 0 0 0 0 1 3
Node 0, zone DMA, type Reclaimable 0 0 0 0
0 0 0 0 0 0 0
Node 0, zone DMA, type HighAtomic 0 0 0 0
0 0 0 0 0 0 0
Node 0, zone DMA, type Isolate 0 0 0 0
0 0 0 0 0 0 0
Node 0, zone DMA32, type Unmovable 0 1 0 1
0 1 0 1 1 0 3
Node 0, zone DMA32, type Movable 66 53 71 57
59 53 49 47 24 2 42
Node 0, zone DMA32, type Reclaimable 0 0 3 1
0 1 1 1 1 0 0
Node 0, zone DMA32, type HighAtomic 0 0 0 0
0 0 0 0 0 0 0
Node 0, zone DMA32, type Isolate 0 0 0 0
0 0 0 0 0 0 0
Node 0, zone Normal, type Unmovable 1 5442 25546 12849
8379 5771 3297 1523 268 0 0
Node 0, zone Normal, type Movable 100322 153229 102511 75583
52007 34284 19259 9465 2014 15 5
Node 0, zone Normal, type Reclaimable 4002 4299 2395 3721
2568 1056 489 177 63 0 0
Node 0, zone Normal, type HighAtomic 0 0 1 3
3 3 1 0 1 0 0
Node 0, zone Normal, type Isolate 0 0 0 0
0 0 0 0 0 0 0
Number of blocks type Unmovable Movable Reclaimable
HighAtomic Isolate
Node 0, zone DMA 1 7 0
0 0
Node 0, zone DMA32 10 1005 1
0 0
Node 0, zone Normal 3411 27125 1207
1 0
Greets,
Stefan
Am 10.09.19 um 07:56 schrieb Stefan Priebe - Profihost AG:
>
> Am 09.09.19 um 14:56 schrieb Stefan Priebe - Profihost AG:
>> Am 09.09.19 um 14:49 schrieb Michal Hocko:
>>> On Mon 09-09-19 14:37:52, Stefan Priebe - Profihost AG wrote:
>>>>
>>>> Am 09.09.19 um 14:28 schrieb Michal Hocko:
>>>>> On Mon 09-09-19 14:10:02, Stefan Priebe - Profihost AG wrote:
>>>>>>
>>>>>> Am 09.09.19 um 14:08 schrieb Michal Hocko:
>>>>>>> On Mon 09-09-19 13:01:36, Michal Hocko wrote:
>>>>>>>> and that matches moments when we reclaimed memory. There seems to be a
>>>>>>>> steady THP allocations flow so maybe this is a source of the direct
>>>>>>>> reclaim?
>>>>>>>
>>>>>>> I was thinking about this some more and THP being a source of reclaim
>>>>>>> sounds quite unlikely. At least in a default configuration because we
>>>>>>> shouldn't do anything expensinve in the #PF path. But there might be a
>>>>>>> difference source of high order (!costly) allocations. Could you check
>>>>>>> how many allocation requests like that you have on your system?
>>>>>>>
>>>>>>> mount -t debugfs none /debug
>>>>>>> echo "order > 0" > /debug/tracing/events/kmem/mm_page_alloc/filter
>>>>>>> echo 1 > /debug/tracing/events/kmem/mm_page_alloc/enable
>>>>>>> cat /debug/tracing/trace_pipe > $file
>>>>>
>>>>> echo 1 > /debug/tracing/events/vmscan/mm_vmscan_direct_reclaim_begin/enable
>>>>> echo 1 > /debug/tracing/events/vmscan/mm_vmscan_direct_reclaim_end/enable
>>>>>
>>>>> might tell us something as well but it might turn out that it just still
>>>>> doesn't give us the full picture and we might need
>>>>> echo stacktrace > /debug/tracing/trace_options
>>>>>
>>>>> It will generate much more output though.
>>>>>
>>>>>> Just now or when PSI raises?
>>>>>
>>>>> When the excessive reclaim is happening ideally.
>>>>
>>>> This one is from a server with 28G memfree but memory pressure is still
>>>> jumping between 0 and 10%.
>>>>
>>>> I did:
>>>> echo "order > 0" >
>>>> /sys/kernel/debug/tracing/events/kmem/mm_page_alloc/filter
>>>>
>>>> echo 1 > /sys/kernel/debug/tracing/events/kmem/mm_page_alloc/enable
>>>>
>>>> echo 1 >
>>>> /sys/kernel/debug/tracing/events/vmscan/mm_vmscan_direct_reclaim_begin/enable
>>>>
>>>> echo 1 >
>>>> /sys/kernel/debug/tracing/events/vmscan/mm_vmscan_direct_reclaim_end/enable
>>>>
>>>> timeout 120 cat /sys/kernel/debug/tracing/trace_pipe > /trace
>>>>
>>>> File attached.
>>>
>>> There is no reclaim captured in this trace dump.
>>> $ zcat trace1.gz | sed 's@.*\(order=[0-9]\).*\(gfp_flags=.*\)@\1 \2@' | sort | uniq -c
>>> 777 order=1 gfp_flags=__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 663 order=1 gfp_flags=__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 153 order=1 gfp_flags=__GFP_IO|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 911 order=1 gfp_flags=GFP_KERNEL_ACCOUNT|__GFP_ZERO
>>> 4872 order=1 gfp_flags=GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_COMP|__GFP_ACCOUNT
>>> 62 order=1 gfp_flags=GFP_NOWAIT|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 14 order=2 gfp_flags=GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP
>>> 11 order=2 gfp_flags=GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_RECLAIMABLE
>>> 1263 order=2 gfp_flags=__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 45 order=2 gfp_flags=__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_RECLAIMABLE
>>> 1 order=2 gfp_flags=GFP_KERNEL|__GFP_COMP|__GFP_ZERO
>>> 7853 order=2 gfp_flags=GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_COMP|__GFP_ACCOUNT
>>> 73 order=3 gfp_flags=__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 729 order=3 gfp_flags=__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_RECLAIMABLE
>>> 528 order=3 gfp_flags=__GFP_IO|__GFP_NOWARN|__GFP_RETRY_MAYFAIL|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 1203 order=3 gfp_flags=GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_COMP|__GFP_ACCOUNT
>>> 5295 order=3 gfp_flags=GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP
>>> 1 order=3 gfp_flags=GFP_NOWAIT|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 132 order=3 gfp_flags=GFP_NOWAIT|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC
>>> 13 order=5 gfp_flags=GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_ZERO
>>> 1 order=6 gfp_flags=GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_ZERO
>>> 1232 order=9 gfp_flags=GFP_TRANSHUGE
>>> 108 order=9 gfp_flags=GFP_TRANSHUGE|__GFP_THISNODE
>>> 362 order=9 gfp_flags=GFP_TRANSHUGE_LIGHT|__GFP_THISNODE
>>>
>>> Nothing really stands out because except for the THP ones none of others
>>> are going to even be using movable zone.
>> It might be that this is not an ideal example is was just the fastest i
>> could find. May be we really need one with much higher pressure.
>
> here another trace log where a system has 30GB free memory but is under
> constant pressure and does not build up any file cache caused by memory
> pressure.
>
>
> Greets,
> Stefan
>
