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Shutemov" To: Zi Yan Cc: akpm@linux-foundation.org, Andrea Arcangeli , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: Re: [PATCH 3/7] khugepaged: Drain LRU add pagevec to get rid of extra pins Message-ID: <20200328002041.5tnoy67ruw7lavwx@box> References: <20200327170601.18563-1-kirill.shutemov@linux.intel.com> <20200327170601.18563-4-kirill.shutemov@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Bogosity: Ham, tests=bogofilter, spamicity=0.000132, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Mar 27, 2020 at 01:34:20PM -0400, Zi Yan wrote: > On 27 Mar 2020, at 13:05, Kirill A. Shutemov wrote: > > > __collapse_huge_page_isolate() may fail due to extra pin in the LRU add > > pagevec. It's petty common for swapin case: we swap in pages just to > > fail due to the extra pin. > > > > Signed-off-by: Kirill A. Shutemov > > --- > > mm/khugepaged.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index 14d7afc90786..39e0994abeb8 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -585,11 +585,19 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, > > * The page must only be referenced by the scanned process > > * and page swap cache. > > */ > > + if (page_count(page) != 1 + PageSwapCache(page)) { > > + /* > > + * Drain pagevec and retry just in case we can get rid > > + * of the extra pin, like in swapin case. > > + */ > > + lru_add_drain(); > > + } > > if (page_count(page) != 1 + PageSwapCache(page)) { > > unlock_page(page); > > result = SCAN_PAGE_COUNT; > > goto out; > > } > > + > > if (pte_write(pteval)) { > > writable = true; > > } else { > > -- > > 2.26.0 > > Looks good to me. Is the added empty line intentional? Yes. It groups try and retry together. -- Kirill A. Shutemov