Re: [PATCH, RFC 00/16] Transparent huge page cache

From: Simon Jeons
Date: Mon Mar 18 2013 - 05:36:17 EST

On 01/28/2013 05:24 PM, Kirill A. Shutemov wrote:
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>

Here's first steps towards huge pages in page cache.

The intend of the work is get code ready to enable transparent huge page
cache for the most simple fs -- ramfs.

It's not yet near feature-complete. It only provides basic infrastructure.
At the moment we can read, write and truncate file on ramfs with huge pages in
page cache. The most interesting part, mmap(), is not yet there. For now
we split huge page on mmap() attempt.

I can't say that I see whole picture. I'm not sure if I understand locking
model around split_huge_page(). Probably, not.
Andrea, could you check if it looks correct?

Another offline question:
Why don't clear tail page PG_tail flag in function __split_huge_page_refcount?

Next steps (not necessary in this order):
- mmap();
- migration (?);
- collapse;
- stats, knobs, etc.;
- tmpfs/shmem enabling;
- ...

Kirill A. Shutemov (16):
block: implement add_bdi_stat()
mm: implement zero_huge_user_segment and friends
mm: drop actor argument of do_generic_file_read()
radix-tree: implement preload for multiple contiguous elements
thp, mm: basic defines for transparent huge page cache
thp, mm: rewrite add_to_page_cache_locked() to support huge pages
thp, mm: rewrite delete_from_page_cache() to support huge pages
thp, mm: locking tail page is a bug
thp, mm: handle tail pages in page_cache_get_speculative()
thp, mm: implement grab_cache_huge_page_write_begin()
thp, mm: naive support of thp in generic read/write routines
thp, libfs: initial support of thp in
thp: handle file pages in split_huge_page()
thp, mm: truncate support for transparent huge page cache
thp, mm: split huge page on mmap file page
ramfs: enable transparent huge page cache

fs/libfs.c | 54 +++++++++---
fs/ramfs/inode.c | 6 +-
include/linux/backing-dev.h | 10 +++
include/linux/huge_mm.h | 8 ++
include/linux/mm.h | 15 ++++
include/linux/pagemap.h | 14 ++-
include/linux/radix-tree.h | 3 +
lib/radix-tree.c | 32 +++++--
mm/filemap.c | 204 +++++++++++++++++++++++++++++++++++--------
mm/huge_memory.c | 62 +++++++++++--
mm/memory.c | 22 +++++
mm/truncate.c | 12 +++
12 files changed, 375 insertions(+), 67 deletions(-)

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