From: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
To: Michal Hocko <mhocko@kernel.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
l.roehrs@profihost.ag, cgroups@vger.kernel.org,
Johannes Weiner <hannes@cmpxchg.org>,
Vlastimil Babka <vbabka@suse.cz>
Subject: Re: lot of MemAvailable but falling cache and raising PSI
Date: Mon, 9 Sep 2019 14:56:39 +0200 [thread overview]
Message-ID: <10fa0b97-631d-f82b-0881-89adb9ad5ded@profihost.ag> (raw)
In-Reply-To: <20190909124950.GN27159@dhcp22.suse.cz>
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.
I would try to find one with much higher pressure.
> You've said that your machine
> doesn't have more than one NUMA node, right?
Yes the first example is / was a VM. This one is a Single Xeon.
Stefan
next prev parent reply other threads:[~2019-09-09 12:56 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-05 11:27 lot of MemAvailable but falling cache and raising PSI Stefan Priebe - Profihost AG
2019-09-05 11:40 ` Michal Hocko
2019-09-05 11:56 ` Stefan Priebe - Profihost AG
2019-09-05 16:28 ` Yang Shi
2019-09-05 17:26 ` Stefan Priebe - Profihost AG
2019-09-05 18:46 ` Yang Shi
2019-09-05 19:31 ` Stefan Priebe - Profihost AG
2019-09-06 10:08 ` Stefan Priebe - Profihost AG
2019-09-06 10:25 ` Vlastimil Babka
2019-09-06 18:52 ` Yang Shi
2019-09-07 7:32 ` Stefan Priebe - Profihost AG
2019-09-09 8:27 ` Michal Hocko
2019-09-09 8:54 ` Stefan Priebe - Profihost AG
2019-09-09 11:01 ` Michal Hocko
2019-09-09 12:08 ` Michal Hocko
2019-09-09 12:10 ` Stefan Priebe - Profihost AG
2019-09-09 12:28 ` Michal Hocko
2019-09-09 12:37 ` Stefan Priebe - Profihost AG
2019-09-09 12:49 ` Michal Hocko
2019-09-09 12:56 ` Stefan Priebe - Profihost AG [this message]
[not found] ` <52235eda-ffe2-721c-7ad7-575048e2d29d@profihost.ag>
2019-09-10 5:58 ` Stefan Priebe - Profihost AG
2019-09-10 8:29 ` Michal Hocko
2019-09-10 8:38 ` Stefan Priebe - Profihost AG
2019-09-10 9:02 ` Michal Hocko
2019-09-10 9:37 ` Stefan Priebe - Profihost AG
2019-09-10 11:07 ` Michal Hocko
2019-09-10 12:45 ` Stefan Priebe - Profihost AG
2019-09-10 12:57 ` Michal Hocko
2019-09-10 13:05 ` Stefan Priebe - Profihost AG
2019-09-10 13:14 ` Stefan Priebe - Profihost AG
2019-09-10 13:24 ` Michal Hocko
2019-09-11 6:12 ` Stefan Priebe - Profihost AG
2019-09-11 6:24 ` Stefan Priebe - Profihost AG
2019-09-11 13:59 ` Stefan Priebe - Profihost AG
2019-09-12 10:53 ` Stefan Priebe - Profihost AG
2019-09-12 11:06 ` Stefan Priebe - Profihost AG
2019-09-11 7:09 ` 5.3-rc-8 hung task in IO (was: Re: lot of MemAvailable but falling cache and raising PSI) Michal Hocko
2019-09-11 14:09 ` Stefan Priebe - Profihost AG
2019-09-11 14:56 ` Filipe Manana
2019-09-11 15:39 ` Stefan Priebe - Profihost AG
2019-09-11 15:56 ` Filipe Manana
2019-09-11 16:15 ` Stefan Priebe - Profihost AG
2019-09-11 16:19 ` Filipe Manana
2019-09-19 10:21 ` lot of MemAvailable but falling cache and raising PSI Stefan Priebe - Profihost AG
2019-09-23 12:08 ` Michal Hocko
2019-09-27 12:45 ` Vlastimil Babka
2019-09-30 6:56 ` Stefan Priebe - Profihost AG
2019-09-30 7:21 ` Vlastimil Babka
2019-10-22 7:41 ` Stefan Priebe - Profihost AG
2019-10-22 7:48 ` Vlastimil Babka
2019-10-22 10:02 ` Stefan Priebe - Profihost AG
2019-10-22 10:20 ` Oscar Salvador
2019-10-22 10:21 ` Vlastimil Babka
2019-10-22 11:08 ` Stefan Priebe - Profihost AG
2019-09-10 5:41 ` Stefan Priebe - Profihost AG
2019-09-09 11:49 ` Vlastimil Babka
2019-09-09 12:09 ` Stefan Priebe - Profihost AG
2019-09-09 12:21 ` Vlastimil Babka
2019-09-09 12:31 ` Stefan Priebe - Profihost AG
2019-09-05 12:15 ` Vlastimil Babka
2019-09-05 12:27 ` Stefan Priebe - Profihost AG
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