Steve Capper
031e6e6b4e
For contiguous hugetlb, huge_ptep_set_access_flags performs a
get_clear_flush (which then flushes the TLBs) even when no change of ptes
is necessary.
Unfortunately, this behaviour can lead to back-to-back page faults being
generated when running with multiple threads that access the same
contiguous huge page.
Thread 1 | Thread 2
-----------------------------+------------------------------
hugetlb_fault |
huge_ptep_set_access_flags |
-> invalidate pte range | hugetlb_fault
continue processing | wait for hugetlb_fault_mutex
release mutex and return | huge_ptep_set_access_flags
| -> invalidate pte range
hugetlb_fault
...
This patch changes huge_ptep_set_access_flags s.t. we first read the
contiguous range of ptes (whilst preserving dirty information); the pte
range is only then invalidated where necessary and this prevents further
spurious page faults.
Fixes: d8bdcff287 ("arm64: hugetlb: Add break-before-make logic for contiguous entries")
Reported-by: Lei Zhang <zhang.lei@jp.fujitsu.com>
Signed-off-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.