From: Yu Zhao <yuzhao@google.com>
To: Mike Rapoport <rppt@kernel.org>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"Andi Kleen" <ak@linux.intel.com>,
"Aneesh Kumar" <aneesh.kumar@linux.ibm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
"Hillf Danton" <hdanton@sina.com>, "Jens Axboe" <axboe@kernel.dk>,
"Jesse Barnes" <jsbarnes@google.com>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Jonathan Corbet" <corbet@lwn.net>,
"Matthew Wilcox" <willy@infradead.org>,
"Mel Gorman" <mgorman@suse.de>,
"Michael Larabel" <Michael@michaellarabel.com>,
"Michal Hocko" <mhocko@kernel.org>,
"Rik van Riel" <riel@surriel.com>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Will Deacon" <will@kernel.org>,
"Ying Huang" <ying.huang@intel.com>,
"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
"Kernel Page Reclaim v2" <page-reclaim@google.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
"Brian Geffon" <bgeffon@google.com>,
"Jan Alexander Steffens" <heftig@archlinux.org>,
"Oleksandr Natalenko" <oleksandr@natalenko.name>,
"Steven Barrett" <steven@liquorix.net>,
"Suleiman Souhlal" <suleiman@google.com>,
"Daniel Byrne" <djbyrne@mtu.edu>,
"Donald Carr" <d@chaos-reins.com>,
"Holger Hoffstätte" <holger@applied-asynchrony.com>,
"Konstantin Kharlamov" <Hi-Angel@yandex.ru>,
"Shuang Zhai" <szhai2@cs.rochester.edu>,
"Sofia Trinh" <sofia.trinh@edi.works>,
"Vaibhav Jain" <vaibhav@linux.ibm.com>
Subject: Re: [PATCH v9 13/14] mm: multi-gen LRU: admin guide
Date: Thu, 10 Mar 2022 17:37:36 -0700 [thread overview]
Message-ID: <CAOUHufbYhRoiFgwbRpz7Ce5tfec7fbUEjk8b9Zty22jz9tN5TA@mail.gmail.com> (raw)
In-Reply-To: <YinvPMIP4oEwCo6T@kernel.org>
On Thu, Mar 10, 2022 at 5:30 AM Mike Rapoport <rppt@kernel.org> wrote:
>
> Hi,
>
> On Tue, Mar 08, 2022 at 07:12:30PM -0700, Yu Zhao wrote:
> > Add an admin guide.
> >
> > Signed-off-by: Yu Zhao <yuzhao@google.com>
> > Acked-by: Brian Geffon <bgeffon@google.com>
> > Acked-by: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
> > Acked-by: Oleksandr Natalenko <oleksandr@natalenko.name>
> > Acked-by: Steven Barrett <steven@liquorix.net>
> > Acked-by: Suleiman Souhlal <suleiman@google.com>
> > Tested-by: Daniel Byrne <djbyrne@mtu.edu>
> > Tested-by: Donald Carr <d@chaos-reins.com>
> > Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
> > Tested-by: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> > Tested-by: Shuang Zhai <szhai2@cs.rochester.edu>
> > Tested-by: Sofia Trinh <sofia.trinh@edi.works>
> > Tested-by: Vaibhav Jain <vaibhav@linux.ibm.com>
> > ---
> > Documentation/admin-guide/mm/index.rst | 1 +
> > Documentation/admin-guide/mm/multigen_lru.rst | 146 ++++++++++++++++++
> > mm/Kconfig | 3 +-
> > 3 files changed, 149 insertions(+), 1 deletion(-)
> > create mode 100644 Documentation/admin-guide/mm/multigen_lru.rst
> >
> > diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst
> > index c21b5823f126..2cf5bae62036 100644
> > --- a/Documentation/admin-guide/mm/index.rst
> > +++ b/Documentation/admin-guide/mm/index.rst
> > @@ -32,6 +32,7 @@ the Linux memory management.
> > idle_page_tracking
> > ksm
> > memory-hotplug
> > + multigen_lru
> > nommu-mmap
> > numa_memory_policy
> > numaperf
> > diff --git a/Documentation/admin-guide/mm/multigen_lru.rst b/Documentation/admin-guide/mm/multigen_lru.rst
> > new file mode 100644
> > index 000000000000..4ea6a801dc56
> > --- /dev/null
> > +++ b/Documentation/admin-guide/mm/multigen_lru.rst
> > @@ -0,0 +1,146 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +=============
> > +Multi-Gen LRU
> > +=============
>
> I'm still missing an opening paragraph the explains what is Multi-gen LRU
> and why users would want it.
>
> Something like
>
> Multi-gen LRU is an efficient mechanism for page reclamation.
>
> More details are of course welcome :)
I've add the following for the next spin:
+Page reclaim decides the kernel's caching policy and ability to
+overcommit memory. It directly impacts the kswapd CPU usage and RAM
+efficiency. Multi-gen LRU aims to optimize page reclaim and improve
+performance under memory pressure.
> > +Quick start
> > +===========
> > +Build the kernel with the following configurations.
> > +
> > +* ``CONFIG_LRU_GEN=y``
> > +* ``CONFIG_LRU_GEN_ENABLED=y``
> > +
> > +All set!
> > +
> > +Runtime options
> > +===============
> > +``/sys/kernel/mm/lru_gen/`` contains stable ABIs described in the
> > +following subsections.
> > +
> > +Kill switch
> > +-----------
> > +``enable`` accepts different values to enable or disabled the
>
> ^ disable
Good catch. Will fix it up.
> > +following components. The default value of this file depends on
> > +``CONFIG_LRU_GEN_ENABLED``. All the components should be enabled
> > +unless some of them have unforeseen side effects. Writing to
> > +``enable`` has no effect when a component is not supported by the
> > +hardware, and valid values will be accepted even when the main switch
> > +is off.
> > +
> > +====== ===============================================================
> > +Values Components
> > +====== ===============================================================
> > +0x0001 The main switch for the multi-gen LRU.
> > +0x0002 Clearing the accessed bit in leaf page table entries in large
> > + batches, when MMU sets it (e.g., on x86). This behavior can
> > + theoretically worsen lock contention (mmap_lock). If it is
> > + disabled, the multi-gen LRU will suffer a minor performance
> > + degradation.
> > +0x0004 Clearing the accessed bit in non-leaf page table entries as
> > + well, when MMU sets it (e.g., on x86). This behavior was not
> > + verified on x86 varieties other than Intel and AMD. If it is
> > + disabled, the multi-gen LRU will suffer a negligible
> > + performance degradation.
> > +[yYnN] Apply to all the components above.
> > +====== ===============================================================
> > +
> > +E.g.,
> > +::
> > +
> > + echo y >/sys/kernel/mm/lru_gen/enabled
> > + cat /sys/kernel/mm/lru_gen/enabled
> > + 0x0007
> > + echo 5 >/sys/kernel/mm/lru_gen/enabled
> > + cat /sys/kernel/mm/lru_gen/enabled
> > + 0x0005
> > +
> > +Thrashing prevention
> > +--------------------
> > +Personal computers are more sensitive to thrashing because it can
> > +cause janks (lags when rendering UI) and negatively impact user
> > +experience. The multi-gen LRU offers thrashing prevention to the
> > +majority of laptop and desktop users who do not have ``oomd``.
> > +
> > +Users can write ``N`` to ``min_ttl_ms`` to prevent the working set of
> > +``N`` milliseconds from getting evicted. The OOM killer is triggered
> > +if this working set cannot be kept in memory. In other words, this
> > +option works as an adjustable pressure relief valve, and when open, it
> > +terminates applications that are hopefully not being used.
> > +
> > +Based on the average human detectable lag (~100ms), ``N=1000`` usually
> > +eliminates intolerable janks due to thrashing. Larger values like
> > +``N=3000`` make janks less noticeable at the risk of premature OOM
> > +kills.
>
> What is the default value of min_ttl_ms?
Right. I've added the following for the next spin:
+The default value ``0`` means disabled.
next prev parent reply other threads:[~2022-03-11 0:37 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 2:12 [PATCH v9 00/14] Multi-Gen LRU Framework Yu Zhao
2022-03-09 2:12 ` [PATCH v9 01/14] mm: x86, arm64: add arch_has_hw_pte_young() Yu Zhao
2022-03-11 10:55 ` Barry Song
2022-03-11 22:57 ` Yu Zhao
2022-03-09 2:12 ` [PATCH v9 02/14] mm: x86: add CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG Yu Zhao
2022-03-16 22:15 ` Barry Song
2022-03-09 2:12 ` [PATCH v9 03/14] mm/vmscan.c: refactor shrink_node() Yu Zhao
2022-03-18 1:15 ` Barry Song
2022-03-09 2:12 ` [PATCH v9 04/14] Revert "include/linux/mm_inline.h: fold __update_lru_size() into its sole caller" Yu Zhao
2022-03-09 2:12 ` [PATCH v9 05/14] mm: multi-gen LRU: groundwork Yu Zhao
2022-03-14 8:08 ` Huang, Ying
2022-03-14 9:30 ` Yu Zhao
2022-03-15 0:34 ` Huang, Ying
2022-03-15 0:50 ` Yu Zhao
2022-03-21 18:58 ` Justin Forbes
2022-03-21 19:17 ` Prarit Bhargava
2022-03-22 4:52 ` Yu Zhao
2022-03-16 23:25 ` Barry Song
2022-03-21 9:04 ` Yu Zhao
2022-03-21 11:47 ` Barry Song
2022-03-09 2:12 ` [PATCH v9 06/14] mm: multi-gen LRU: minimal implementation Yu Zhao
2022-03-16 5:55 ` Huang, Ying
2022-03-16 7:54 ` Yu Zhao
2022-03-19 3:01 ` Barry Song
2022-03-19 3:11 ` Yu Zhao
2022-03-23 7:47 ` Barry Song
2022-03-24 6:24 ` Yu Zhao
2022-03-24 8:13 ` Barry Song
2022-03-19 10:14 ` Barry Song
2022-03-21 23:51 ` Yu Zhao
2022-03-19 11:15 ` Barry Song
2022-03-22 0:30 ` Yu Zhao
2022-03-21 12:51 ` Aneesh Kumar K.V
2022-03-22 4:02 ` Yu Zhao
2022-03-21 13:01 ` Aneesh Kumar K.V
2022-03-22 4:39 ` Yu Zhao
2022-03-22 5:26 ` Aneesh Kumar K.V
2022-03-22 5:55 ` Yu Zhao
2022-03-09 2:12 ` [PATCH v9 07/14] mm: multi-gen LRU: exploit locality in rmap Yu Zhao
2022-04-07 2:29 ` Barry Song
2022-04-07 3:04 ` Yu Zhao
2022-04-07 3:46 ` Barry Song
2022-04-07 23:51 ` Yu Zhao
2022-03-09 2:12 ` [PATCH v9 08/14] mm: multi-gen LRU: support page table walks Yu Zhao
2022-03-09 2:12 ` [PATCH v9 09/14] mm: multi-gen LRU: optimize multiple memcgs Yu Zhao
2022-03-09 2:12 ` [PATCH v9 10/14] mm: multi-gen LRU: kill switch Yu Zhao
2022-03-22 7:47 ` Barry Song
2022-03-22 8:20 ` Yu Zhao
2022-03-22 8:45 ` Barry Song
2022-03-22 9:00 ` Yu Zhao
2022-03-09 2:12 ` [PATCH v9 11/14] mm: multi-gen LRU: thrashing prevention Yu Zhao
2022-03-22 7:22 ` Barry Song
2022-03-22 8:14 ` Yu Zhao
2022-03-09 2:12 ` [PATCH v9 12/14] mm: multi-gen LRU: debugfs interface Yu Zhao
2022-03-09 2:12 ` [PATCH v9 13/14] mm: multi-gen LRU: admin guide Yu Zhao
2022-03-10 12:29 ` Mike Rapoport
2022-03-11 0:37 ` Yu Zhao [this message]
2022-03-09 2:12 ` [PATCH v9 14/14] mm: multi-gen LRU: design doc Yu Zhao
2022-03-11 8:22 ` Mike Rapoport
2022-03-11 9:38 ` Yu Zhao
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