From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Dave Chinner <david@fromorbit.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Hugh Dickins <hughd@google.com>,
Wu Fengguang <fengguang.wu@intel.com>, Jan Kara <jack@suse.cz>,
Mel Gorman <mgorman@suse.de>,
linux-mm@kvack.org, Andi Kleen <ak@linux.intel.com>,
Matthew Wilcox <willy@linux.intel.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Hillf Danton <dhillf@gmail.com>, Dave Hansen <dave@sr71.net>,
Ning Qu <quning@google.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHv6 00/22] Transparent huge page cache: phase 1, everything but mmap()
Date: Mon, 14 Oct 2013 16:56:41 +0300 (EEST) [thread overview]
Message-ID: <20131014135642.05DFEE0090@blue.fi.intel.com> (raw)
In-Reply-To: <20130925232915.GK26872@dastard>
Dave Chinner wrote:
> On Wed, Sep 25, 2013 at 12:51:04PM +0300, Kirill A. Shutemov wrote:
> > Andrew Morton wrote:
> > > On Mon, 23 Sep 2013 15:05:28 +0300 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> wrote:
> > >
> > > > It brings thp support for ramfs, but without mmap() -- it will be posted
> > > > separately.
> > >
> > > We were never going to do this :(
> > >
> > > Has anyone reviewed these patches much yet?
> >
> > Dave did very good review. Few other people looked to separate patches.
> > See Reviewed-by/Acked-by tags in patches.
> >
> > It looks like most mm experts are busy with numa balancing nowadays, so
> > it's hard to get more review.
>
> Nobody has reviewed it from the filesystem side, though.
>
> The changes that require special code paths for huge pages in the
> write_begin/write_end paths are nasty. You're adding conditional
> code that depends on the page size and then having to add checks to
> ensure that large page operations don't step over small page
> boundaries and other such corner cases. It's an extremely fragile
> design, IMO.
>
> In general, I don't like all the if (thp) {} else {}; code that this
> series introduces - they are code paths that simply won't get tested
> with any sort of regularity and make the code more complex for those
> that aren't using THP to understand and debug...
Okay, I'll try to get rid of special cases where it's possible.
> Then there is a new per-inode lock that is used in
> generic_perform_write() which is held across page faults and calls
> to filesystem block mapping callbacks. This inserts into the middle
> of an existing locking chain that needs to be strictly ordered, and
> as such will lead to the same type of lock inversion problems that
> the mmap_sem had. We do not want to introduce a new lock that has
> this same problem just as we are getting rid of that long standing
> nastiness from the page fault path...
I don't see how we can protect against splitting with existing locks,
but I'll try find a way.
> I also note that you didn't convert invalidate_inode_pages2_range()
> to support huge pages which is needed by real filesystems that
> support direct IO. There are other truncate/invalidate interfaces
> that you didn't convert, either, and some of them will present you
> with interesting locking challenges as a result of adding that new
> lock...
Thanks. I'll take a look on these code paths.
> > The patchset was mostly ignored for few rounds and Dave suggested to split
> > to have less scary patch number.
>
> It's still being ignored by filesystem people because you haven't
> actually tried to implement support into a real filesystem.....
If it will support a real filesystem, wouldn't it be ignored due
patch count? ;)
> > > > Please review and consider applying.
> > >
> > > It appears rather too immature at this stage.
> >
> > More review is always welcome and I'm committed to address issues.
>
> IMO, supporting a real block based filesystem like ext4 or XFS and
> demonstrating that everything works is necessary before we go any
> further...
Will see what numbers I can bring in next iterations.
Thanks for your feedback. And sorry for late answer.
--
Kirill A. Shutemov
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next prev parent reply other threads:[~2013-10-14 13:56 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-23 12:05 [PATCHv6 00/22] Transparent huge page cache: phase 1, everything but mmap() Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 01/22] mm: implement zero_huge_user_segment and friends Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 02/22] radix-tree: implement preload for multiple contiguous elements Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 03/22] memcg, thp: charge huge cache pages Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 04/22] thp: compile-time and sysfs knob for thp pagecache Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 05/22] thp, mm: introduce mapping_can_have_hugepages() predicate Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 06/22] thp: represent file thp pages in meminfo and friends Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 07/22] thp, mm: rewrite add_to_page_cache_locked() to support huge pages Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 08/22] mm: trace filemap: dump page order Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 09/22] block: implement add_bdi_stat() Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 10/22] thp, mm: rewrite delete_from_page_cache() to support huge pages Kirill A. Shutemov
2013-09-25 20:02 ` Ning Qu
2013-09-23 12:05 ` [PATCHv6 11/22] thp, mm: warn if we try to use replace_page_cache_page() with THP Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 12/22] thp, mm: add event counters for huge page alloc on file write or read Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 13/22] mm, vfs: introduce i_split_sem Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 14/22] thp, mm: allocate huge pages in grab_cache_page_write_begin() Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 15/22] thp, mm: naive support of thp in generic_perform_write Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 16/22] thp, mm: handle transhuge pages in do_generic_file_read() Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 17/22] thp, libfs: initial thp support Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 18/22] truncate: support huge pages Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 19/22] thp: handle file pages in split_huge_page() Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 20/22] thp: wait_split_huge_page(): serialize over i_mmap_mutex too Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 21/22] thp, mm: split huge page on mmap file page Kirill A. Shutemov
2013-09-23 12:05 ` [PATCHv6 22/22] ramfs: enable transparent huge page cache Kirill A. Shutemov
2013-09-24 23:37 ` [PATCHv6 00/22] Transparent huge page cache: phase 1, everything but mmap() Andrew Morton
2013-09-24 23:48 ` Ning Qu
2013-09-24 23:49 ` Andi Kleen
2013-09-24 23:58 ` Andrew Morton
2013-09-25 11:15 ` Kirill A. Shutemov
2013-09-25 15:05 ` Andi Kleen
2013-09-26 18:30 ` Zach Brown
2013-09-26 19:05 ` Andi Kleen
2013-09-30 10:13 ` Mel Gorman
2013-09-30 16:05 ` Andi Kleen
2013-09-25 9:51 ` Kirill A. Shutemov
2013-09-25 23:29 ` Dave Chinner
2013-10-14 13:56 ` Kirill A. Shutemov [this message]
2013-09-30 10:02 ` Mel Gorman
2013-09-30 10:10 ` Mel Gorman
2013-09-30 18:07 ` Ning Qu
2013-09-30 18:51 ` Andi Kleen
2013-10-01 8:38 ` Mel Gorman
2013-10-01 17:11 ` Ning Qu
2013-10-14 14:27 ` Kirill A. Shutemov
2013-09-30 15:27 ` Dave Hansen
2013-09-30 18:05 ` Ning Qu
2013-09-25 0:12 ` Ning Qu
2013-09-25 9:23 ` Kirill A. Shutemov
2013-09-26 21:13 ` Dave Hansen
-- strict thread matches above, loose matches on Subject: below --
2013-09-25 18:11 Ning Qu
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