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mm: support POSIX_FADV_NOREUSE 

JIRA: https://issues.redhat.com/browse/RHEL-27740
Tested: by me
Conflicts: due d8aeb44a9ae32 being already backported

commit 17e810229cb3068b692fa078bd9b3a6527e0866a
Author: Yu Zhao <yuzhao@google.com>
Date:   Fri Dec 30 14:52:52 2022 -0700

    mm: support POSIX_FADV_NOREUSE

    This patch adds POSIX_FADV_NOREUSE to vma_has_recency() so that the LRU
    algorithm can ignore access to mapped files marked by this flag.

    The advantages of POSIX_FADV_NOREUSE are:
    1. Unlike MADV_SEQUENTIAL and MADV_RANDOM, it does not alter the
       default readahead behavior.
    2. Unlike MADV_SEQUENTIAL and MADV_RANDOM, it does not split VMAs and
       therefore does not take mmap_lock.
    3. Unlike MADV_COLD, setting it has a negligible cost, regardless of
       how many pages it affects.

    Its limitations are:
    1. Like POSIX_FADV_RANDOM and POSIX_FADV_SEQUENTIAL, it currently does
       not support range. IOW, its scope is the entire file.
    2. It currently does not ignore access through file descriptors.
       Specifically, for the active/inactive LRU, given a file page shared
       by two users and one of them having set POSIX_FADV_NOREUSE on the
       file, this page will be activated upon the second user accessing
       it. This corner case can be covered by checking POSIX_FADV_NOREUSE
       before calling folio_mark_accessed() on the read path. But it is
       considered not worth the effort.

    There have been a few attempts to support POSIX_FADV_NOREUSE, e.g., [1].
    This time the goal is to fill a niche: a few desktop applications, e.g.,
    large file transferring and video encoding/decoding, want fast file
    streaming with mmap() rather than direct IO.  Among those applications, an
    SVT-AV1 regression was reported when running with MGLRU [2].  The
    following test can reproduce that regression.

      kb=$(awk '/MemTotal/ { print $2 }' /proc/meminfo)
      kb=$((kb - 8*1024*1024))

      modprobe brd rd_nr=1 rd_size=$kb
      dd if=/dev/zero of=/dev/ram0 bs=1M

      mkfs.ext4 /dev/ram0
      mount /dev/ram0 /mnt/
      swapoff -a

      fallocate -l 8G /mnt/swapfile
      mkswap /mnt/swapfile
      swapon /mnt/swapfile

      wget http://ultravideo.cs.tut.fi/video/Bosphorus_3840x2160_120fps_420_8bit_YUV_Y4M.7z
      7z e -o/mnt/ Bosphorus_3840x2160_120fps_420_8bit_YUV_Y4M.7z
      SvtAv1EncApp --preset 12 -w 3840 -h 2160 \
                   -i /mnt/Bosphorus_3840x2160.y4m

    For MGLRU, the following change showed a [9-11]% increase in FPS,
    which makes it on par with the active/inactive LRU.

      patch Source/App/EncApp/EbAppMain.c <<EOF
      31a32
      > #include <fcntl.h>
      35d35
      < #include <fcntl.h> /* _O_BINARY */
      117a118
      >             posix_fadvise(config->mmap.fd, 0, 0, POSIX_FADV_NOREUSE);
      EOF

    [1] https://lore.kernel.org/r/1308923350-7932-1-git-send-email-andrea@betterlinux.com/
    [2] https://openbenchmarking.org/result/2209259-PTS-MGLRU8GB57

    Link: https://lkml.kernel.org/r/20221230215252.2628425-2-yuzhao@google.com
    Signed-off-by: Yu Zhao <yuzhao@google.com>
    Cc: Alexander Viro <viro@zeniv.linux.org.uk>
    Cc: Andrea Righi <andrea.righi@canonical.com>
    Cc: Johannes Weiner <hannes@cmpxchg.org>
    Cc: Michael Larabel <Michael@MichaelLarabel.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Aristeu Rozanski <arozansk@redhat.com>
This commit is contained in:
Aristeu Rozanski 2024-04-29 14:32:56 -04:00
parent d908e3177a
commit d065bbcc54
3 changed files with 9 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/fs.h
View File

@ -161,6 +161,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
/* File supports DIRECT IO */
#define FMODE_CAN_ODIRECT ((__force fmode_t)0x400000)
#define FMODE_NOREUSE ((__force fmode_t)0x800000)
/* File supports non-exclusive O_DIRECT writes from multiple threads */
#define FMODE_DIO_PARALLEL_WRITE ((__force fmode_t)0x1000000)

3
include/linux/mm_inline.h
View File

@ -604,6 +604,9 @@ static inline bool vma_has_recency(struct vm_area_struct *vma)
if (vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))
return false;
if (vma->vm_file && (vma->vm_file->f_mode & FMODE_NOREUSE))
return false;
return true;
}

5
mm/fadvise.c
View File

@ -80,7 +80,7 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
case POSIX_FADV_NORMAL:
file->f_ra.ra_pages = bdi->ra_pages;
spin_lock(&file->f_lock);
file->f_mode &= ~FMODE_RANDOM;
file->f_mode &= ~(FMODE_RANDOM | FMODE_NOREUSE);
spin_unlock(&file->f_lock);
break;
case POSIX_FADV_RANDOM:
@ -107,6 +107,9 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
force_page_cache_readahead(mapping, file, start_index, nrpages);
break;
case POSIX_FADV_NOREUSE:
spin_lock(&file->f_lock);
file->f_mode |= FMODE_NOREUSE;
spin_unlock(&file->f_lock);
break;
case POSIX_FADV_DONTNEED:
__filemap_fdatawrite_range(mapping, offset, endbyte,