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Shutemov" To: David Hildenbrand Cc: Michal Hocko , Andrew Morton , Dan Williams , Vlastimil Babka , Mel Gorman , "Jin, Zhi" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: Re: [PATCH] mm/page_alloc: Skip non present sections on zone initialization Message-ID: <20200110134547.v6ju5dxazknfjdj3@box> References: <20191230093828.24613-1-kirill.shutemov@linux.intel.com> <20200108144044.GB30379@dhcp22.suse.cz> <73437651-822f-fcec-3b96-281fb1064cf8@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <73437651-822f-fcec-3b96-281fb1064cf8@redhat.com> User-Agent: NeoMutt/20180716 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 Fri, Jan 10, 2020 at 02:15:26PM +0100, David Hildenbrand wrote: > On 08.01.20 15:40, Michal Hocko wrote: > > On Mon 30-12-19 12:38:28, Kirill A. Shutemov wrote: > >> memmap_init_zone() can be called on the ranges with holes during the > >> boot. It will skip any non-valid PFNs one-by-one. It works fine as long > >> as holes are not too big. > >> > >> But huge holes in the memory map causes a problem. It takes over 20 > >> seconds to walk 32TiB hole. x86-64 with 5-level paging allows for much > >> larger holes in the memory map which would practically hang the system. > >> > >> Deferred struct page init doesn't help here. It only works on the > >> present ranges. > >> > >> Skipping non-present sections would fix the issue. > > > > Makes sense to me. > > > >> Signed-off-by: Kirill A. Shutemov > > > > That pfn inc back and forth is quite ugly TBH but whatever. > > Indeed, can we please rewrite the loop to fix that? Any suggestions? I don't see an obvious way to not break readablity in another place. -- Kirill A. Shutemov