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From: Michal Hocko <mhocko@kernel.org>
To: Stefan Priebe - Profihost AG <s.priebe@profihost.ag>
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 14:49:50 +0200
Message-ID: <20190909124950.GN27159@dhcp22.suse.cz> (raw)
In-Reply-To: <2d04fc69-8fac-2900-013b-7377ca5fd9a8@profihost.ag>

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. You've said that your machine
doesn't have more than one NUMA node, right?
-- 
Michal Hocko
SUSE Labs


  reply index

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-05 11:27 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 [this message]
2019-09-09 12:56                       ` Stefan Priebe - Profihost AG
     [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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