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Shutemov" To: "Matthew Wilcox (Oracle)" 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 Message-ID: <20220117160625.oofpzl7tqm5udwaj@box.shutemov.name> References: <20220116121822.1727633-1-willy@infradead.org> <20220116121822.1727633-5-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220116121822.1727633-5-willy@infradead.org> X-Rspamd-Queue-Id: 9B012A0009 X-Stat-Signature: r3hwkcs6zxpnjze7n88tnm6b4xsdggof Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=shutemov-name.20210112.gappssmtp.com header.s=20210112 header.b=y4LkLPTo; dmarc=none; spf=none (imf25.hostedemail.com: domain of kirill@shutemov.name has no SPF policy when checking 209.85.167.42) smtp.mailfrom=kirill@shutemov.name X-Rspamd-Server: rspam02 X-HE-Tag: 1642435558-295293 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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? > 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()? > Unfortunately, we still have to split shmem THPs > because we can't handle swapping out an entire THP yet. ... especially if the system doesn't have swap :P > > Signed-off-by: Matthew Wilcox (Oracle) > --- > mm/vmscan.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 700434db5735..45665874082d 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1728,8 +1728,8 @@ static unsigned int shrink_page_list(struct list_head *page_list, > /* Adding to swap updated mapping */ > mapping = page_mapping(page); > } > - } else if (unlikely(PageTransHuge(page))) { > - /* Split file THP */ > + } else if (PageSwapBacked(page) && PageTransHuge(page)) { > + /* Split shmem THP */ > if (split_huge_page_to_list(page, page_list)) > goto keep_locked; > } > -- > 2.34.1 > -- Kirill A. Shutemov