16 Jan, 2016
40 commits
-
When I test below piece of code with 12 processes(ie, 512M * 12 = 6G
consume) on my (3G ram + 12 cpu + 8G swap, the madvise_free is
siginficat slower (ie, 2x times) than madvise_dontneed.loop = 5;
mmap(512M);
while (loop--) {
memset(512M);
madvise(MADV_FREE or MADV_DONTNEED);
}The reason is lots of swapin.
1) dontneed: 1,612 swapin
2) madvfree: 879,585 swapinIf we find hinted pages were already swapped out when syscall is called,
it's pointless to keep the swapped-out pages in pte. Instead, let's
free the cold page because swapin is more expensive than (alloc page +
zeroing).With this patch, it reduced swapin from 879,585 to 1,878 so elapsed time
1) dontneed: 6.10user 233.50system 0:50.44elapsed
2) madvfree: 6.03user 401.17system 1:30.67elapsed
2) madvfree + below patch: 6.70user 339.14system 1:04.45elapsedSigned-off-by: Minchan Kim
Acked-by: Michal Hocko
Acked-by: Hugh Dickins
Cc: "James E.J. Bottomley"
Cc: "Kirill A. Shutemov"
Cc: Shaohua Li
Cc:
Cc: Andrea Arcangeli
Cc: Andy Lutomirski
Cc: Arnd Bergmann
Cc: Benjamin Herrenschmidt
Cc: Catalin Marinas
Cc: Chen Gang
Cc: Chris Zankel
Cc: Daniel Micay
Cc: Darrick J. Wong
Cc: David S. Miller
Cc: Helge Deller
Cc: Ivan Kokshaysky
Cc: Jason Evans
Cc: Johannes Weiner
Cc: KOSAKI Motohiro
Cc: Kirill A. Shutemov
Cc: Matt Turner
Cc: Max Filippov
Cc: Mel Gorman
Cc: Michael Kerrisk
Cc: Mika Penttil
Cc: Ralf Baechle
Cc: Richard Henderson
Cc: Rik van Riel
Cc: Roland Dreier
Cc: Russell King
Cc: Shaohua Li
Cc: Will Deacon
Cc: Wu Fengguang
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
For uapi, need try to let all macros have same value, and MADV_FREE is
added into main branch recently, so need redefine MADV_FREE for it.At present, '8' can be shared with all architectures, so redefine it to
'8'.[sudipm.mukherjee@gmail.com: correct uniform value of MADV_FREE]
Signed-off-by: Chen Gang
Signed-off-by: Minchan Kim
Acked-by: Hugh Dickins
Cc: Ralf Baechle
Cc: Arnd Bergmann
Cc: Richard Henderson
Cc: Ivan Kokshaysky
Cc: Matt Turner
Cc: "James E.J. Bottomley"
Cc: Helge Deller
Cc: Chris Zankel
Cc: Max Filippov
Cc: Roland Dreier
Cc: Darrick J. Wong
Cc: David S. Miller
Cc: "Kirill A. Shutemov"
Cc: Shaohua Li
Cc:
Cc: Andrea Arcangeli
Cc: Andy Lutomirski
Cc: Arnd Bergmann
Cc: Benjamin Herrenschmidt
Cc: Catalin Marinas
Cc: Daniel Micay
Cc: Jason Evans
Cc: Johannes Weiner
Cc: KOSAKI Motohiro
Cc: Kirill A. Shutemov
Cc: Mel Gorman
Cc: Michael Kerrisk
Cc: Michal Hocko
Cc: Mika Penttil
Cc: Rik van Riel
Cc: Russell King
Cc: Shaohua Li
Cc: Will Deacon
Cc: Wu Fengguang
Signed-off-by: Sudip Mukherjee
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Most architectures use asm-generic, but alpha, mips, parisc, xtensa need
their own definitions.This patch defines MADV_FREE for them so it should fix build break for
their architectures.Maybe, I should split and feed pieces to arch maintainers but included
here for mmotm convenience.[gang.chen.5i5j@gmail.com: let MADV_FREE have same value for all architectures]
Signed-off-by: Minchan Kim
Acked-by: Max Filippov
Cc: Wu Fengguang
Cc: Michael Kerrisk
Cc: Richard Henderson
Cc: Ivan Kokshaysky
Cc: "James E.J. Bottomley"
Cc: Helge Deller
Cc: Ralf Baechle
Cc: Chris Zankel
Cc: "Kirill A. Shutemov"
Cc: Shaohua Li
Cc:
Cc: Andrea Arcangeli
Cc: Andy Lutomirski
Cc: Arnd Bergmann
Cc: Benjamin Herrenschmidt
Cc: Catalin Marinas
Cc: Chen Gang
Cc: Daniel Micay
Cc: Darrick J. Wong
Cc: David S. Miller
Cc: Hugh Dickins
Cc: Jason Evans
Cc: Johannes Weiner
Cc: KOSAKI Motohiro
Cc: Kirill A. Shutemov
Cc: Matt Turner
Cc: Mel Gorman
Cc: Michal Hocko
Cc: Mika Penttil
Cc: Rik van Riel
Cc: Roland Dreier
Cc: Russell King
Cc: Shaohua Li
Cc: Will Deacon
Signed-off-by: Chen Gang
Acked-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Linux doesn't have an ability to free pages lazy while other OS already
have been supported that named by madvise(MADV_FREE).The gain is clear that kernel can discard freed pages rather than
swapping out or OOM if memory pressure happens.Without memory pressure, freed pages would be reused by userspace
without another additional overhead(ex, page fault + allocation +
zeroing).Jason Evans said:
: Facebook has been using MAP_UNINITIALIZED
: (https://lkml.org/lkml/2012/1/18/308) in some of its applications for
: several years, but there are operational costs to maintaining this
: out-of-tree in our kernel and in jemalloc, and we are anxious to retire it
: in favor of MADV_FREE. When we first enabled MAP_UNINITIALIZED it
: increased throughput for much of our workload by ~5%, and although the
: benefit has decreased using newer hardware and kernels, there is still
: enough benefit that we cannot reasonably retire it without a replacement.
:
: Aside from Facebook operations, there are numerous broadly used
: applications that would benefit from MADV_FREE. The ones that immediately
: come to mind are redis, varnish, and MariaDB. I don't have much insight
: into Android internals and development process, but I would hope to see
: MADV_FREE support eventually end up there as well to benefit applications
: linked with the integrated jemalloc.
:
: jemalloc will use MADV_FREE once it becomes available in the Linux kernel.
: In fact, jemalloc already uses MADV_FREE or equivalent everywhere it's
: available: *BSD, OS X, Windows, and Solaris -- every platform except Linux
: (and AIX, but I'm not sure it even compiles on AIX). The lack of
: MADV_FREE on Linux forced me down a long series of increasingly
: sophisticated heuristics for madvise() volume reduction, and even so this
: remains a common performance issue for people using jemalloc on Linux.
: Please integrate MADV_FREE; many people will benefit substantially.How it works:
When madvise syscall is called, VM clears dirty bit of ptes of the
range. If memory pressure happens, VM checks dirty bit of page table
and if it found still "clean", it means it's a "lazyfree pages" so VM
could discard the page instead of swapping out. Once there was store
operation for the page before VM peek a page to reclaim, dirty bit is
set so VM can swap out the page instead of discarding.One thing we should notice is that basically, MADV_FREE relies on dirty
bit in page table entry to decide whether VM allows to discard the page
or not. IOW, if page table entry includes marked dirty bit, VM
shouldn't discard the page.However, as a example, if swap-in by read fault happens, page table
entry doesn't have dirty bit so MADV_FREE could discard the page
wrongly.For avoiding the problem, MADV_FREE did more checks with PageDirty and
PageSwapCache. It worked out because swapped-in page lives on swap
cache and since it is evicted from the swap cache, the page has PG_dirty
flag. So both page flags check effectively prevent wrong discarding by
MADV_FREE.However, a problem in above logic is that swapped-in page has PG_dirty
still after they are removed from swap cache so VM cannot consider the
page as freeable any more even if madvise_free is called in future.Look at below example for detail.
ptr = malloc();
memset(ptr);
..
..
.. heavy memory pressure so all of pages are swapped out
..
..
var = *ptr; -> a page swapped-in and could be removed from
swapcache. Then, page table doesn't mark
dirty bit and page descriptor includes PG_dirty
..
..
madvise_free(ptr); -> It doesn't clear PG_dirty of the page.
..
..
..
.. heavy memory pressure again.
.. In this time, VM cannot discard the page because the page
.. has *PG_dirty*To solve the problem, this patch clears PG_dirty if only the page is
owned exclusively by current process when madvise is called because
PG_dirty represents ptes's dirtiness in several processes so we could
clear it only if we own it exclusively.Firstly, heavy users would be general allocators(ex, jemalloc, tcmalloc
and hope glibc supports it) and jemalloc/tcmalloc already have supported
the feature for other OS(ex, FreeBSD)barrios@blaptop:~/benchmark/ebizzy$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 12
On-line CPU(s) list: 0-11
Thread(s) per core: 1
Core(s) per socket: 1
Socket(s): 12
NUMA node(s): 1
Vendor ID: GenuineIntel
CPU family: 6
Model: 2
Stepping: 3
CPU MHz: 3200.185
BogoMIPS: 6400.53
Virtualization: VT-x
Hypervisor vendor: KVM
Virtualization type: full
L1d cache: 32K
L1i cache: 32K
L2 cache: 4096K
NUMA node0 CPU(s): 0-11
ebizzy benchmark(./ebizzy -S 10 -n 512)Higher avg is better.
vanilla-jemalloc MADV_free-jemalloc
1 thread
records: 10 records: 10
avg: 2961.90 avg: 12069.70
std: 71.96(2.43%) std: 186.68(1.55%)
max: 3070.00 max: 12385.00
min: 2796.00 min: 11746.002 thread
records: 10 records: 10
avg: 5020.00 avg: 17827.00
std: 264.87(5.28%) std: 358.52(2.01%)
max: 5244.00 max: 18760.00
min: 4251.00 min: 17382.004 thread
records: 10 records: 10
avg: 8988.80 avg: 27930.80
std: 1175.33(13.08%) std: 3317.33(11.88%)
max: 9508.00 max: 30879.00
min: 5477.00 min: 21024.008 thread
records: 10 records: 10
avg: 13036.50 avg: 33739.40
std: 170.67(1.31%) std: 5146.22(15.25%)
max: 13371.00 max: 40572.00
min: 12785.00 min: 24088.0016 thread
records: 10 records: 10
avg: 11092.40 avg: 31424.20
std: 710.60(6.41%) std: 3763.89(11.98%)
max: 12446.00 max: 36635.00
min: 9949.00 min: 25669.0032 thread
records: 10 records: 10
avg: 11067.00 avg: 34495.80
std: 971.06(8.77%) std: 2721.36(7.89%)
max: 12010.00 max: 38598.00
min: 9002.00 min: 30636.00In summary, MADV_FREE is about much faster than MADV_DONTNEED.
This patch (of 12):
Add core MADV_FREE implementation.
[akpm@linux-foundation.org: small cleanups]
Signed-off-by: Minchan Kim
Acked-by: Michal Hocko
Acked-by: Hugh Dickins
Cc: Mika Penttil
Cc: Michael Kerrisk
Cc: Johannes Weiner
Cc: Rik van Riel
Cc: Mel Gorman
Cc: KOSAKI Motohiro
Cc: Jason Evans
Cc: Daniel Micay
Cc: "Kirill A. Shutemov"
Cc: Shaohua Li
Cc:
Cc: Andy Lutomirski
Cc: "James E.J. Bottomley"
Cc: "Kirill A. Shutemov"
Cc: "Shaohua Li"
Cc: Andrea Arcangeli
Cc: Arnd Bergmann
Cc: Benjamin Herrenschmidt
Cc: Catalin Marinas
Cc: Chen Gang
Cc: Chris Zankel
Cc: Darrick J. Wong
Cc: David S. Miller
Cc: Helge Deller
Cc: Ivan Kokshaysky
Cc: Matt Turner
Cc: Max Filippov
Cc: Ralf Baechle
Cc: Richard Henderson
Cc: Roland Dreier
Cc: Russell King
Cc: Shaohua Li
Cc: Will Deacon
Cc: Wu Fengguang
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The use of idr_remove() is forbidden in the callback functions of
idr_for_each(). It is therefore unsafe to call idr_remove in
zram_remove().This patch moves the call to idr_remove() from zram_remove() to
hot_remove_store(). In the detroy_devices() path, idrs are removed by
idr_destroy(). This solves an use-after-free detected by KASan.[akpm@linux-foundation.org: fix coding stype, per Sergey]
Signed-off-by: Jerome Marchand
Acked-by: Sergey Senozhatsky
Cc: Minchan Kim
Cc: [4.2+]
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
page_referenced_one() and page_idle_clear_pte_refs_one() duplicate the
code for looking up pte of a (possibly transhuge) page. Move this code
to a new helper function, page_check_address_transhuge(), and make the
above mentioned functions use it.This is just a cleanup, no functional changes are intended.
Signed-off-by: Vladimir Davydov
Reviewed-by: Kirill A. Shutemov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
During freeze_page(), we remove the page from rmap. It munlocks the
page if it was mlocked. clear_page_mlock() uses thelru cache, which
temporary pins the page.Let's drain the lru cache before checking page's count vs. mapcount.
The change makes mlocked page split on first attempt, if it was not
pinned by somebody else.Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Acked-by: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Writing 1 into 'split_huge_pages' will try to find and split all huge
pages in the system. This is useful for debuging.[akpm@linux-foundation.org: fix printk text, per Vlastimil]
Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Andrea Arcangeli
Acked-by: Vlastimil Babka
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Both page_referenced() and page_idle_clear_pte_refs_one() assume that
THP can only be mapped with PMD, so there's no reason to look on PTEs
for PageTransHuge() pages. That's no true anymore: THP can be mapped
with PTEs too.The patch removes PageTransHuge() test from the functions and opencode
page table check.[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Kirill A. Shutemov
Cc: Vladimir Davydov
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Naoya Horiguchi
Cc: Sasha Levin
Cc: Minchan Kim
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Before THP refcounting rework, THP was not allowed to cross VMA
boundary. So, if we have THP and we split it, PG_mlocked can be safely
transferred to small pages.With new THP refcounting and naive approach to mlocking we can end up
with this scenario:
1. we have a mlocked THP, which belong to one VM_LOCKED VMA.
2. the process does munlock() on the *part* of the THP:
- the VMA is split into two, one of them VM_LOCKED;
- huge PMD split into PTE table;
- THP is still mlocked;
3. split_huge_page():
- it transfers PG_mlocked to *all* small pages regrardless if it
blong to any VM_LOCKED VMA.We probably could munlock() all small pages on split_huge_page(), but I
think we have accounting issue already on step two.Instead of forbidding mlocked pages altogether, we just avoid mlocking
PTE-mapped THPs and munlock THPs on split_huge_pmd().This means PTE-mapped THPs will be on normal lru lists and will be split
under memory pressure by vmscan. After the split vmscan will detect
unevictable small pages and mlock them.With this approach we shouldn't hit situation like described above.
Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The patch updates Documentation/vm/transhuge.txt to reflect changes in
THP design.Signed-off-by: Kirill A. Shutemov
Acked-by: Jerome Marchand
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
All parts of THP with new refcounting are now in place. We can now
allow to enable THP.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Currently we don't split huge page on partial unmap. It's not an ideal
situation. It can lead to memory overhead.Furtunately, we can detect partial unmap on page_remove_rmap(). But we
cannot call split_huge_page() from there due to locking context.It's also counterproductive to do directly from munmap() codepath: in
many cases we will hit this from exit(2) and splitting the huge page
just to free it up in small pages is not what we really want.The patch introduce deferred_split_huge_page() which put the huge page
into queue for splitting. The splitting itself will happen when we get
memory pressure via shrinker interface. The page will be dropped from
list on freeing through compound page destructor.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We are not able to migrate THPs. It means it's not enough to split only
PMD on migration -- we need to split compound page under it too.Signed-off-by: Kirill A. Shutemov
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Sasha Levin
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
This patch adds implementation of split_huge_page() for new
refcountings.Unlike previous implementation, new split_huge_page() can fail if
somebody holds GUP pin on the page. It also means that pin on page
would prevent it from bening split under you. It makes situation in
many places much cleaner.The basic scheme of split_huge_page():
- Check that sum of mapcounts of all subpage is equal to page_count()
plus one (caller pin). Foll off with -EBUSY. This way we can avoid
useless PMD-splits.- Freeze the page counters by splitting all PMD and setup migration
PTEs.- Re-check sum of mapcounts against page_count(). Page's counts are
stable now. -EBUSY if page is pinned.- Split compound page.
- Unfreeze the page by removing migration entries.
Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David RientjesSigned-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Some mm-related BUG_ON()s could trigger from hwpoison code due to recent
changes in thp refcounting rule. This patch fixes them up.In the new refcounting, we no longer use tail->_mapcount to keep tail's
refcount, and thereby we can simplify get/put_hwpoison_page().And another change is that tail's refcount is not transferred to the raw
page during thp split (more precisely, in new rule we don't take
refcount on tail page any more.) So when we need thp split, we have to
transfer the refcount properly to the 4kB soft-offlined page before
migration.thp split code goes into core code only when precheck
(total_mapcount(head) == page_count(head) - 1) passes to avoid useless
split, where we assume that one refcount is held by the caller of thp
split and the others are taken via mapping. To meet this assumption,
this patch moves thp split part in soft_offline_page() after
get_any_page().[akpm@linux-foundation.org: remove unneeded #define, per Kirill]
Signed-off-by: Naoya Horiguchi
Acked-by: Kirill A. Shutemov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
I saw the following BUG_ON triggered in a testcase where a process calls
madvise(MADV_SOFT_OFFLINE) on thps, along with a background process that
calls migratepages command repeatedly (doing ping-pong among different
NUMA nodes) for the first process:Soft offlining page 0x60000 at 0x700000600000
__get_any_page: 0x60000 free buddy page
page:ffffea0001800000 count:0 mapcount:-127 mapping: (null) index:0x1
flags: 0x1fffc0000000000()
page dumped because: VM_BUG_ON_PAGE(atomic_read(&page->_count) == 0)
------------[ cut here ]------------
kernel BUG at /src/linux-dev/include/linux/mm.h:342!
invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC
Modules linked in: cfg80211 rfkill crc32c_intel serio_raw virtio_balloon i2c_piix4 virtio_blk virtio_net ata_generic pata_acpi
CPU: 3 PID: 3035 Comm: test_alloc_gene Tainted: G O 4.4.0-rc8-v4.4-rc8-160107-1501-00000-rc8+ #74
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
task: ffff88007c63d5c0 ti: ffff88007c210000 task.ti: ffff88007c210000
RIP: 0010:[] [] put_page+0x5c/0x60
RSP: 0018:ffff88007c213e00 EFLAGS: 00010246
Call Trace:
put_hwpoison_page+0x4e/0x80
soft_offline_page+0x501/0x520
SyS_madvise+0x6bc/0x6f0
entry_SYSCALL_64_fastpath+0x12/0x6a
Code: 8b fc ff ff 5b 5d c3 48 89 df e8 b0 fa ff ff 48 89 df 31 f6 e8 c6 7d ff ff 5b 5d c3 48 c7 c6 08 54 a2 81 48 89 df e8 a4 c5 01 00 0b 66 90 66 66 66 66 90 55 48 89 e5 41 55 41 54 53 48 8b 47
RIP [] put_page+0x5c/0x60
RSPThe root cause resides in get_any_page() which retries to get a refcount
of the page to be soft-offlined. This function calls
put_hwpoison_page(), expecting that the target page is putback to LRU
list. But it can be also freed to buddy. So the second check need to
care about such case.Fixes: af8fae7c0886 ("mm/memory-failure.c: clean up soft_offline_page()")
Signed-off-by: Naoya Horiguchi
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Vlastimil Babka
Cc: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Cc: [3.9+]
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We're going to use migration entries instead of compound_lock() to
stabilize page refcounts. Setup and remove migration entries require
page to be locked.Some of split_huge_page() callers already have the page locked. Let's
require everybody to lock the page before calling split_huge_page().Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We are going to use migration PTE entries to stabilize page counts. If
the page is mapped with PMDs we need to split the PMD and setup
migration entries. It's reasonable to combine these operations to avoid
double-scanning over the page table.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Original split_huge_page() combined two operations: splitting PMDs into
tables of PTEs and splitting underlying compound page. This patch
implements split_huge_pmd() which split given PMD without splitting
other PMDs this page mapped with or underlying compound page.Without tail page refcounting, implementation of split_huge_pmd() is
pretty straight-forward.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We're going to have THP mapped with PTEs. It will confuse
numabalancing. Let's skip them for now.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Let's define page_mapped() to be true for compound pages if any
sub-pages of the compound page is mapped (with PMD or PTE).On other hand page_mapcount() return mapcount for this particular small
page.This will make cases like page_get_anon_vma() behave correctly once we
allow huge pages to be mapped with PTE.Most users outside core-mm should use page_mapcount() instead of
page_mapped().Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We're going to allow mapping of individual 4k pages of THP compound. It
means we need to track mapcount on per small page basis.Straight-forward approach is to use ->_mapcount in all subpages to track
how many time this subpage is mapped with PMDs or PTEs combined. But
this is rather expensive: mapping or unmapping of a THP page with PMD
would require HPAGE_PMD_NR atomic operations instead of single we have
now.The idea is to store separately how many times the page was mapped as
whole -- compound_mapcount. This frees up ->_mapcount in subpages to
track PTE mapcount.We use the same approach as with compound page destructor and compound
order to store compound_mapcount: use space in first tail page,
->mapping this time.Any time we map/unmap whole compound page (THP or hugetlb) -- we
increment/decrement compound_mapcount. When we map part of compound
page with PTE we operate on ->_mapcount of the subpage.page_mapcount() counts both: PTE and PMD mappings of the page.
Basically, we have mapcount for a subpage spread over two counters. It
makes tricky to detect when last mapcount for a page goes away.We introduced PageDoubleMap() for this. When we split THP PMD for the
first time and there's other PMD mapping left we offset up ->_mapcount
in all subpages by one and set PG_double_map on the compound page.
These additional references go away with last compound_mapcount.This approach provides a way to detect when last mapcount goes away on
per small page basis without introducing new overhead for most common
cases.[akpm@linux-foundation.org: fix typo in comment]
[mhocko@suse.com: ignore partial THP when moving task]
Signed-off-by: Kirill A. Shutemov
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Michal Hocko
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Acked-by: Jerome Marchand
Cc: Aneesh Kumar K.V
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as
needed for fast_gup.Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as
needed for fast_gup.Signed-off-by: Kirill A. Shutemov
Tested-by: Aneesh Kumar K.V
Reviewed-by: Aneesh Kumar K.V
Cc: Sasha Levin
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as
needed for fast_gup.Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as
needed for fast_gup.[arnd@arndb.de: fix unterminated ifdef in header file]
Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Vlastimil Babka
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Arnd Bergmann
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.pmdp_splitting_flush() is not needed too: on splitting PMD we will do
pmdp_clear_flush() + set_pte_at(). pmdp_clear_flush() will do IPI as
needed for fast_gup.Signed-off-by: Kirill A. Shutemov
Cc: Sasha Levin
Cc: Aneesh Kumar K.V
Cc: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We are going to use migration entries to stabilize page counts. It
means we don't need compound_lock() for that.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We don't need special code to stabilize THP. If you've got reference to
any subpage of THP it will not be split under you.New split_huge_page() also accepts tail pages: no need in special code
to get reference to head page.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
With new THP refcounting, we don't need tricks to stabilize huge page.
If we've got reference to tail page, it can't split under us.This patch effectively reverts a5b338f2b0b1 ("thp: update futex compound
knowledge").Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Tested-by: Artem Savkov
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Tail page refcounting is utterly complicated and painful to support.
It uses ->_mapcount on tail pages to store how many times this page is
pinned. get_page() bumps ->_mapcount on tail page in addition to
->_count on head. This information is required by split_huge_page() to
be able to distribute pins from head of compound page to tails during
the split.We will need ->_mapcount to account PTE mappings of subpages of the
compound page. We eliminate need in current meaning of ->_mapcount in
tail pages by forbidding split entirely if the page is pinned.The only user of tail page refcounting is THP which is marked BROKEN for
now.Let's drop all this mess. It makes get_page() and put_page() much
simpler.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Vlastimil Babka
Acked-by: Jerome Marchand
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We will re-introduce new version with new refcounting later in patchset.
Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Up to this point we tried to keep patchset bisectable, but next patches
are going to change how core of THP refcounting work.It would be beneficial to split the change into several patches and make
it more reviewable. Unfortunately, I don't see how we can achieve that
while keeping THP working.Let's hide THP under CONFIG_BROKEN for now and bring it back when new
refcounting get established.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Cc: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
The patch replaces THP_SPLIT with tree events: THP_SPLIT_PAGE,
THP_SPLIT_PAGE_FAILED and THP_SPLIT_PMD. It reflects the fact that we
are going to be able split PMD without the compound page and that
split_huge_page() can fail.Signed-off-by: Kirill A. Shutemov
Acked-by: Christoph Lameter
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Acked-by: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We are going to decouple splitting THP PMD from splitting underlying
compound page.This patch renames split_huge_page_pmd*() functions to split_huge_pmd*()
to reflect the fact that it doesn't imply page splitting, only PMD.Signed-off-by: Kirill A. Shutemov
Tested-by: Sasha Levin
Tested-by: Aneesh Kumar K.V
Acked-by: Jerome Marchand
Acked-by: Vlastimil Babka
Cc: Andrea Arcangeli
Cc: Hugh Dickins
Cc: Dave Hansen
Cc: Mel Gorman
Cc: Rik van Riel
Cc: Naoya Horiguchi
Cc: Steve Capper
Cc: Johannes Weiner
Cc: Michal Hocko
Cc: Christoph Lameter
Cc: David Rientjes
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
