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Chinwen Chang ff9f47f6f0 mm: proc: smaps_rollup: do not stall write attempts on mmap_lock
smaps_rollup will try to grab mmap_lock and go through the whole vma list
until it finishes the iterating.  When encountering large processes, the
mmap_lock will be held for a longer time, which may block other write
requests like mmap and munmap from progressing smoothly.

There are upcoming mmap_lock optimizations like range-based locks, but the
lock applied to smaps_rollup would be the coarse type, which doesn't avoid
the occurrence of unpleasant contention.

To solve aforementioned issue, we add a check which detects whether anyone
wants to grab mmap_lock for write attempts.

Signed-off-by: Chinwen Chang <chinwen.chang@mediatek.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Chinwen Chang <chinwen.chang@mediatek.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Song Liu <songliubraving@fb.com>
Cc: Jimmy Assarsson <jimmyassarsson@gmail.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Daniel Kiss <daniel.kiss@arm.com>
Cc: Laurent Dufour <ldufour@linux.ibm.com>
Link: http://lkml.kernel.org/r/1597715898-3854-4-git-send-email-chinwen.chang@mediatek.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-10-13 18:38:31 -07:00
arch mm: account PMD tables like PTE tables 2020-10-13 18:38:31 -07:00
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Documentation mm: memcontrol: add the missing numa_stat interface for cgroup v2 2020-10-13 18:38:30 -07:00
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include mmap locking API: add mmap_lock_is_contended() 2020-10-13 18:38:31 -07:00
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Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.