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From: Naoya Horiguchi To: Kemeng Shi Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@infradead.org, naoya.horiguchi@nec.com, osalvador@suse.de Subject: Re: [PATCH v2 2/3] mm/page_alloc: remove unnecessary check in break_down_buddy_pages Message-ID: <20230926113400.GB1539169@ik1-406-35019.vs.sakura.ne.jp> References: <20230826154745.4019371-1-shikemeng@huaweicloud.com> <20230826154745.4019371-3-shikemeng@huaweicloud.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230826154745.4019371-3-shikemeng@huaweicloud.com> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 52F334001F X-Stat-Signature: we3xezcdixdnxsw58wtj88tn7f1npg5i X-Rspam-User: X-HE-Tag: 1695728051-997204 X-HE-Meta: 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 6kMz2YDC opiEheHGyxLmVvCLPs95+QHhCUfucABGZnkns7Uzl1msVw3XpwtcXFddZnTNlPNZmvGNM2aSnPTwmGq5+meN+5TQM/bfVLVLScOGleQS0WG8WtNzRK0eAo2ZijpwKRhzGM1PXriZxUSoopOCFzZqln/NgxwIIxJ2qB5ulz/2k6ozjNac= 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 Sat, Aug 26, 2023 at 11:47:44PM +0800, Kemeng Shi wrote: > 1. We always have target in range started with next_page and full free > range started with current_buddy. > 2. The last splited range size is 1 << low and low should be >= 0, then s/splited/split/ > size >= 1, then page + size and page will not interleave. I'm not sure the meaning of "interleave" here, maybe simply meaning "page + size != page is always true (because size > 0)". > As summary, current_page will not equal to target page. > > Signed-off-by: Kemeng Shi But I agree with the summary. So with updating description... Acked-by: Naoya Horiguchi > --- > mm/page_alloc.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 88c5f5aea9b0..bb74b40dc195 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -6510,10 +6510,8 @@ static void break_down_buddy_pages(struct zone *zone, struct page *page, > if (set_page_guard(zone, current_buddy, high, migratetype)) > continue; > > - if (current_buddy != target) { > - add_to_free_list(current_buddy, zone, high, migratetype); > - set_buddy_order(current_buddy, high); > - } > + add_to_free_list(current_buddy, zone, high, migratetype); > + set_buddy_order(current_buddy, high); > } > } > > -- > 2.30.0 > > >