From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 04/12] mm/vmscan: Free non-shmem folios without splitting them
Date: Tue, 18 Jan 2022 00:00:57 +0300 [thread overview]
Message-ID: <20220117210057.o2aug2unmovufrdz@box.shutemov.name> (raw)
In-Reply-To: <YeWVBkgYMp4MctTW@casper.infradead.org>
On Mon, Jan 17, 2022 at 04:10:46PM +0000, Matthew Wilcox wrote:
> On Mon, Jan 17, 2022 at 07:06:25PM +0300, Kirill A. Shutemov wrote:
> > On Sun, Jan 16, 2022 at 12:18:14PM +0000, Matthew Wilcox (Oracle) wrote:
> > > We have to allocate memory in order to split a file-backed folio, so
> > > it's not a good idea to split them in the memory freeing path.
> >
> > Could elaborate on why split a file-backed folio requires memory
> > allocation?
>
> In the commit message or explain it to you now?
>
> We need to allocate xarray nodes to store all the newly-independent
> pages. With a folio that's more than 64 entries in size (current
> implementation), we elide the lowest layer of the radix tree. But
> with any data structure that tracks folios, we'll need to create
> space in it to track N folios instead of 1.
Looks good.
> > > It also
> > > doesn't work for XFS because pages have an extra reference count from
> > > page_has_private() and split_huge_page() expects that reference to have
> > > already been removed.
> >
> > Need to adjust can_split_huge_page()?
>
> no?
I meant we can make can_split_huge_page() expect extra pin if
page_has_private() is true. If it is the only thing that stops
split_huge_page() from handling XFS pages.
--
Kirill A. Shutemov
next prev parent reply other threads:[~2022-01-17 21:00 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-16 12:18 [PATCH 00/12] Enabling large folios for 5.17 Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 01/12] mm: Add folio_put_refs() Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 02/12] filemap: Use folio_put_refs() in filemap_free_folio() Matthew Wilcox (Oracle)
2022-01-17 15:56 ` Kirill A. Shutemov
2022-01-17 16:11 ` Matthew Wilcox
2022-01-16 12:18 ` [PATCH 03/12] filemap: Allow large folios to be added to the page cache Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 04/12] mm/vmscan: Free non-shmem folios without splitting them Matthew Wilcox (Oracle)
2022-01-17 16:06 ` Kirill A. Shutemov
2022-01-17 16:10 ` Matthew Wilcox
2022-01-17 21:00 ` Kirill A. Shutemov [this message]
2022-01-16 12:18 ` [PATCH 05/12] mm: Fix READ_ONLY_THP warning Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 06/12] mm/vmscan: Optimise shrink_page_list for non-PMD-sized folios Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 07/12] mm: Make large folios depend on THP Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 08/12] mm/readahead: Add large folio readahead Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 09/12] mm/readahead: Align file mappings for non-DAX Matthew Wilcox (Oracle)
2022-01-17 3:17 ` Rongwei Wang
2022-01-17 4:40 ` Matthew Wilcox
2022-01-16 12:18 ` [PATCH 10/12] mm/readahead: Switch to page_cache_ra_order Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 11/12] mm/filemap: Support VM_HUGEPAGE for file mappings Matthew Wilcox (Oracle)
2022-01-16 12:18 ` [PATCH 12/12] selftests/vm/transhuge-stress: Support file-backed PMD folios Matthew Wilcox (Oracle)
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