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Message-Id: <1574166203-151975-10-git-send-email-alex.shi@linux.alibaba.com>
Date: Tue, 19 Nov 2019 20:23:23 +0800
From: Alex Shi <alex.shi@...ux.alibaba.com>
To: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, akpm@...ux-foundation.org,
mgorman@...hsingularity.net, tj@...nel.org, hughd@...gle.com,
khlebnikov@...dex-team.ru, daniel.m.jordan@...cle.com,
yang.shi@...ux.alibaba.com, willy@...radead.org,
shakeelb@...gle.com, hannes@...xchg.org
Cc: Alex Shi <alex.shi@...ux.alibaba.com>,
Jason Gunthorpe <jgg@...pe.ca>,
Dan Williams <dan.j.williams@...el.com>,
Vlastimil Babka <vbabka@...e.cz>,
Ira Weiny <ira.weiny@...el.com>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Jann Horn <jannh@...gle.com>,
Logan Gunthorpe <logang@...tatee.com>,
Souptick Joarder <jrdr.linux@...il.com>,
Ralph Campbell <rcampbell@...dia.com>,
"Tobin C. Harding" <tobin@...nel.org>,
Michal Hocko <mhocko@...e.com>,
Oscar Salvador <osalvador@...e.de>,
Wei Yang <richard.weiyang@...il.com>,
Arun KS <arunks@...eaurora.org>,
"Darrick J. Wong" <darrick.wong@...cle.com>,
Amir Goldstein <amir73il@...il.com>,
Dave Chinner <dchinner@...hat.com>,
Josef Bacik <josef@...icpanda.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Jérôme Glisse <jglisse@...hat.com>,
Mike Kravetz <mike.kravetz@...cle.com>,
Kirill Tkhai <ktkhai@...tuozzo.com>,
Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH v4 9/9] mm/lru: revise the comments of lru_lock
Since we changed the pgdat->lru_lock to lruvec->lru_lock, it's time to
fix the incorrect comments in code. Also fixed some zone->lru_lock comment
error from ancient time. etc.
Originally-from: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Jason Gunthorpe <jgg@...pe.ca>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Ira Weiny <ira.weiny@...el.com>
Cc: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: Jann Horn <jannh@...gle.com>
Cc: Logan Gunthorpe <logang@...tatee.com>
Cc: Souptick Joarder <jrdr.linux@...il.com>
Cc: Ralph Campbell <rcampbell@...dia.com>
Cc: "Tobin C. Harding" <tobin@...nel.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Wei Yang <richard.weiyang@...il.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Arun KS <arunks@...eaurora.org>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: "Darrick J. Wong" <darrick.wong@...cle.com>
Cc: Amir Goldstein <amir73il@...il.com>
Cc: Dave Chinner <dchinner@...hat.com>
Cc: Josef Bacik <josef@...icpanda.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: "Jérôme Glisse" <jglisse@...hat.com>
Cc: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Hugh Dickins <hughd@...gle.com>
Cc: Kirill Tkhai <ktkhai@...tuozzo.com>
Cc: Daniel Jordan <daniel.m.jordan@...cle.com>
Cc: Yafang Shao <laoar.shao@...il.com>
Cc: Yang Shi <yang.shi@...ux.alibaba.com>
Cc: cgroups@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org
---
Documentation/admin-guide/cgroup-v1/memcg_test.rst | 15 +++------------
Documentation/admin-guide/cgroup-v1/memory.rst | 6 +++---
Documentation/trace/events-kmem.rst | 2 +-
Documentation/vm/unevictable-lru.rst | 22 ++++++++--------------
include/linux/mm_types.h | 2 +-
include/linux/mmzone.h | 2 +-
mm/filemap.c | 4 ++--
mm/rmap.c | 2 +-
mm/vmscan.c | 12 ++++++++----
9 files changed, 28 insertions(+), 39 deletions(-)
diff --git a/Documentation/admin-guide/cgroup-v1/memcg_test.rst b/Documentation/admin-guide/cgroup-v1/memcg_test.rst
index 3f7115e07b5d..0b9f91589d3d 100644
--- a/Documentation/admin-guide/cgroup-v1/memcg_test.rst
+++ b/Documentation/admin-guide/cgroup-v1/memcg_test.rst
@@ -133,18 +133,9 @@ Under below explanation, we assume CONFIG_MEM_RES_CTRL_SWAP=y.
8. LRU
======
- Each memcg has its own private LRU. Now, its handling is under global
- VM's control (means that it's handled under global pgdat->lru_lock).
- Almost all routines around memcg's LRU is called by global LRU's
- list management functions under pgdat->lru_lock.
-
- A special function is mem_cgroup_isolate_pages(). This scans
- memcg's private LRU and call __isolate_lru_page() to extract a page
- from LRU.
-
- (By __isolate_lru_page(), the page is removed from both of global and
- private LRU.)
-
+ Each memcg has its own vector of LRUs (inactive anon, active anon,
+ inactive file, active file, unevictable) of pages from each node,
+ each LRU handled under a single lru_lock for that memcg and node.
9. Typical Tests.
=================
diff --git a/Documentation/admin-guide/cgroup-v1/memory.rst b/Documentation/admin-guide/cgroup-v1/memory.rst
index 0ae4f564c2d6..60d97e8b7f3c 100644
--- a/Documentation/admin-guide/cgroup-v1/memory.rst
+++ b/Documentation/admin-guide/cgroup-v1/memory.rst
@@ -297,13 +297,13 @@ When oom event notifier is registered, event will be delivered.
PG_locked.
mm->page_table_lock
- pgdat->lru_lock
+ lruvec->lru_lock
lock_page_cgroup.
In many cases, just lock_page_cgroup() is called.
- per-zone-per-cgroup LRU (cgroup's private LRU) is just guarded by
- pgdat->lru_lock, it has no lock of its own.
+ per-node-per-cgroup LRU (cgroup's private LRU) is just guarded by
+ lruvec->lru_lock, it has no lock of its own.
2.7 Kernel Memory Extension (CONFIG_MEMCG_KMEM)
-----------------------------------------------
diff --git a/Documentation/trace/events-kmem.rst b/Documentation/trace/events-kmem.rst
index 555484110e36..68fa75247488 100644
--- a/Documentation/trace/events-kmem.rst
+++ b/Documentation/trace/events-kmem.rst
@@ -69,7 +69,7 @@ When pages are freed in batch, the also mm_page_free_batched is triggered.
Broadly speaking, pages are taken off the LRU lock in bulk and
freed in batch with a page list. Significant amounts of activity here could
indicate that the system is under memory pressure and can also indicate
-contention on the zone->lru_lock.
+contention on the lruvec->lru_lock.
4. Per-CPU Allocator Activity
=============================
diff --git a/Documentation/vm/unevictable-lru.rst b/Documentation/vm/unevictable-lru.rst
index 17d0861b0f1d..0e1490524f53 100644
--- a/Documentation/vm/unevictable-lru.rst
+++ b/Documentation/vm/unevictable-lru.rst
@@ -33,7 +33,7 @@ reclaim in Linux. The problems have been observed at customer sites on large
memory x86_64 systems.
To illustrate this with an example, a non-NUMA x86_64 platform with 128GB of
-main memory will have over 32 million 4k pages in a single zone. When a large
+main memory will have over 32 million 4k pages in a single node. When a large
fraction of these pages are not evictable for any reason [see below], vmscan
will spend a lot of time scanning the LRU lists looking for the small fraction
of pages that are evictable. This can result in a situation where all CPUs are
@@ -55,7 +55,7 @@ unevictable, either by definition or by circumstance, in the future.
The Unevictable Page List
-------------------------
-The Unevictable LRU infrastructure consists of an additional, per-zone, LRU list
+The Unevictable LRU infrastructure consists of an additional, per-node, LRU list
called the "unevictable" list and an associated page flag, PG_unevictable, to
indicate that the page is being managed on the unevictable list.
@@ -84,15 +84,9 @@ The unevictable list does not differentiate between file-backed and anonymous,
swap-backed pages. This differentiation is only important while the pages are,
in fact, evictable.
-The unevictable list benefits from the "arrayification" of the per-zone LRU
+The unevictable list benefits from the "arrayification" of the per-node LRU
lists and statistics originally proposed and posted by Christoph Lameter.
-The unevictable list does not use the LRU pagevec mechanism. Rather,
-unevictable pages are placed directly on the page's zone's unevictable list
-under the zone lru_lock. This allows us to prevent the stranding of pages on
-the unevictable list when one task has the page isolated from the LRU and other
-tasks are changing the "evictability" state of the page.
-
Memory Control Group Interaction
--------------------------------
@@ -101,8 +95,8 @@ The unevictable LRU facility interacts with the memory control group [aka
memory controller; see Documentation/admin-guide/cgroup-v1/memory.rst] by extending the
lru_list enum.
-The memory controller data structure automatically gets a per-zone unevictable
-list as a result of the "arrayification" of the per-zone LRU lists (one per
+The memory controller data structure automatically gets a per-node unevictable
+list as a result of the "arrayification" of the per-node LRU lists (one per
lru_list enum element). The memory controller tracks the movement of pages to
and from the unevictable list.
@@ -196,7 +190,7 @@ for the sake of expediency, to leave a unevictable page on one of the regular
active/inactive LRU lists for vmscan to deal with. vmscan checks for such
pages in all of the shrink_{active|inactive|page}_list() functions and will
"cull" such pages that it encounters: that is, it diverts those pages to the
-unevictable list for the zone being scanned.
+unevictable list for the node being scanned.
There may be situations where a page is mapped into a VM_LOCKED VMA, but the
page is not marked as PG_mlocked. Such pages will make it all the way to
@@ -328,7 +322,7 @@ If the page was NOT already mlocked, mlock_vma_page() attempts to isolate the
page from the LRU, as it is likely on the appropriate active or inactive list
at that time. If the isolate_lru_page() succeeds, mlock_vma_page() will put
back the page - by calling putback_lru_page() - which will notice that the page
-is now mlocked and divert the page to the zone's unevictable list. If
+is now mlocked and divert the page to the node's unevictable list. If
mlock_vma_page() is unable to isolate the page from the LRU, vmscan will handle
it later if and when it attempts to reclaim the page.
@@ -603,7 +597,7 @@ Some examples of these unevictable pages on the LRU lists are:
unevictable list in mlock_vma_page().
shrink_inactive_list() also diverts any unevictable pages that it finds on the
-inactive lists to the appropriate zone's unevictable list.
+inactive lists to the appropriate node's unevictable list.
shrink_inactive_list() should only see SHM_LOCK'd pages that became SHM_LOCK'd
after shrink_active_list() had moved them to the inactive list, or pages mapped
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 270aa8fd2800..ff08a6a8145c 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -78,7 +78,7 @@ struct page {
struct { /* Page cache and anonymous pages */
/**
* @lru: Pageout list, eg. active_list protected by
- * pgdat->lru_lock. Sometimes used as a generic list
+ * lruvec->lru_lock. Sometimes used as a generic list
* by the page owner.
*/
struct list_head lru;
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a9334c8d42c8..58ce3186df78 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -115,7 +115,7 @@ static inline bool free_area_empty(struct free_area *area, int migratetype)
struct pglist_data;
/*
- * zone->lock and the zone lru_lock are two of the hottest locks in the kernel.
+ * zone->lock and the lru_lock are two of the hottest locks in the kernel.
* So add a wild amount of padding here to ensure that they fall into separate
* cachelines. There are very few zone structures in the machine, so space
* consumption is not a concern here.
diff --git a/mm/filemap.c b/mm/filemap.c
index 1f5731768222..65236af31db3 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -101,8 +101,8 @@
* ->swap_lock (try_to_unmap_one)
* ->private_lock (try_to_unmap_one)
* ->i_pages lock (try_to_unmap_one)
- * ->pgdat->lru_lock (follow_page->mark_page_accessed)
- * ->pgdat->lru_lock (check_pte_range->isolate_lru_page)
+ * ->lruvec->lru_lock (follow_page->mark_page_accessed)
+ * ->lruvec->lru_lock (check_pte_range->isolate_lru_page)
* ->private_lock (page_remove_rmap->set_page_dirty)
* ->i_pages lock (page_remove_rmap->set_page_dirty)
* bdi.wb->list_lock (page_remove_rmap->set_page_dirty)
diff --git a/mm/rmap.c b/mm/rmap.c
index 95f381bbaf7f..b32a15d34a9e 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -27,7 +27,7 @@
* mapping->i_mmap_rwsem
* anon_vma->rwsem
* mm->page_table_lock or pte_lock
- * pgdat->lru_lock (in mark_page_accessed, isolate_lru_page)
+ * lruvec->lru_lock (in mark_page_accessed, isolate_lru_page)
* swap_lock (in swap_duplicate, swap_info_get)
* mmlist_lock (in mmput, drain_mmlist and others)
* mapping->private_lock (in __set_page_dirty_buffers)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index ba57c55a6a41..14e09c14977d 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1612,14 +1612,16 @@ static __always_inline void update_lru_sizes(struct lruvec *lruvec,
}
/**
- * pgdat->lru_lock is heavily contended. Some of the functions that
+ * Isolating page from the lruvec to fill in @dst list by nr_to_scan times.
+ *
+ * lruvec->lru_lock is heavily contended. Some of the functions that
* shrink the lists perform better by taking out a batch of pages
* and working on them outside the LRU lock.
*
* For pagecache intensive workloads, this function is the hottest
* spot in the kernel (apart from copy_*_user functions).
*
- * Appropriate locks must be held before calling this function.
+ * Lru_lock must be held before calling this function.
*
* @nr_to_scan: The number of eligible pages to look through on the list.
* @lruvec: The LRU vector to pull pages from.
@@ -1807,14 +1809,16 @@ static int too_many_isolated(struct pglist_data *pgdat, int file,
/*
* This moves pages from @list to corresponding LRU list.
+ * The pages from @list is out of any lruvec, and in the end list reuses as
+ * pages_to_free list.
*
* We move them the other way if the page is referenced by one or more
* processes, from rmap.
*
* If the pages are mostly unmapped, the processing is fast and it is
- * appropriate to hold zone_lru_lock across the whole operation. But if
+ * appropriate to hold lru_lock across the whole operation. But if
* the pages are mapped, the processing is slow (page_referenced()) so we
- * should drop zone_lru_lock around each page. It's impossible to balance
+ * should drop lru_lock around each page. It's impossible to balance
* this, so instead we remove the pages from the LRU while processing them.
* It is safe to rely on PG_active against the non-LRU pages in here because
* nobody will play with that bit on a non-LRU page.
--
1.8.3.1
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