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Filename Latest commit message Latest commit date
Li Xinhai 2e235c3a95 mm/hugetlb.c: fix unnecessary address expansion of pmd sharing
commit a1ba9da8f0f9a37d900ff7eff66482cf7de8015e upstream.

The current code would unnecessarily expand the address range.  Consider
one example, (start, end) = (1G-2M, 3G+2M), and (vm_start, vm_end) =
(1G-4M, 3G+4M), the expected adjustment should be keep (1G-2M, 3G+2M)
without expand.  But the current result will be (1G-4M, 3G+4M).  Actually,
the range (1G-4M, 1G) and (3G, 3G+4M) would never been involved in pmd
sharing.

After this patch, we will check that the vma span at least one PUD aligned
size and the start,end range overlap the aligned range of vma.

With above example, the aligned vma range is (1G, 3G), so if (start, end)
range is within (1G-4M, 1G), or within (3G, 3G+4M), then no adjustment to
both start and end.  Otherwise, we will have chance to adjust start
downwards or end upwards without exceeding (vm_start, vm_end).

Mike:

: The 'adjusted range' is used for calls to mmu notifiers and cache(tlb)
: flushing.  Since the current code unnecessarily expands the range in some
: cases, more entries than necessary would be flushed.  This would/could
: result in performance degradation.  However, this is highly dependent on
: the user runtime.  Is there a combination of vma layout and calls to
: actually hit this issue?  If the issue is hit, will those entries
: unnecessarily flushed be used again and need to be unnecessarily reloaded?

Link: https://lkml.kernel.org/r/20210104081631.2921415-1-lixinhai.lxh@gmail.com
Fixes: 75802ca66354 ("mm/hugetlb: fix calculation of adjust_range_if_pmd_sharing_possible")
Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-07 12:20:43 +01:00
arch MIPS: VDSO: Use CLANG_FLAGS instead of filtering out '--target=' 2021-03-07 12:20:41 +01:00
block blk-settings: align max_sectors on "logical_block_size" boundary 2021-03-04 10:26:40 +01:00
certs certs: Fix blacklist flag type confusion 2021-03-04 10:26:29 +01:00
crypto crypto: ecdh_helper - Ensure 'len >= secret.len' in decode_key() 2021-03-04 10:26:25 +01:00
Documentation seq_file: document how per-entry resources are managed. 2021-03-04 10:26:48 +01:00
drivers nbd: handle device refs for DESTROY_ON_DISCONNECT properly 2021-03-07 12:20:42 +01:00
fs xfs: Fix assert failure in xfs_setattr_size() 2021-03-07 12:20:42 +01:00
include net: sched: fix police ext initialization 2021-03-04 10:26:53 +01:00
init fgraph: Initialize tracing_graph_pause at task creation 2021-02-10 09:25:29 +01:00
ipc
kernel printk: fix deadlock when kernel panic 2021-03-04 10:26:50 +01:00
lib udp: fix skb_copy_and_csum_datagram with odd segment sizes 2021-02-17 10:35:19 +01:00
LICENSES
mm mm/hugetlb.c: fix unnecessary address expansion of pmd sharing 2021-03-07 12:20:43 +01:00
net net: fix up truesize of cloned skb in skb_prepare_for_shift() 2021-03-07 12:20:42 +01:00
samples samples: bpf: Fix lwt_len_hist reusing previous BPF map 2020-12-30 11:51:12 +01:00
scripts scripts/recordmcount.pl: support big endian for ARCH sh 2021-02-26 10:10:28 +01:00
security smackfs: restrict bytes count in smackfs write functions 2021-03-07 12:20:42 +01:00
sound ALSA: hda/realtek: modify EAPD in the ALC886 2021-03-04 10:26:42 +01:00
tools perf test: Fix unaligned access in sample parsing test 2021-03-04 10:26:35 +01:00
usr
virt KVM: Use kvm_pfn_t for local PFN variable in hva_to_pfn_remapped() 2021-02-26 10:10:28 +01:00
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Makefile Linux 5.4.102 2021-03-04 10:26:54 +01:00
README

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.