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From: Kent Overstreet To: Song Liu Cc: Mike Rapoport , linux-mm@kvack.org, Andrew Morton , Dave Hansen , Peter Zijlstra , Rick Edgecombe , Thomas Gleixner , Vlastimil Babka , linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [RFC PATCH 1/5] mm: intorduce __GFP_UNMAPPED and unmapped_alloc() Message-ID: References: <20230518152354.GD4967@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 547EE100012 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 7s3jy3m34437pz5sjhgf99f37wtb1wfs X-HE-Tag: 1684440828-936624 X-HE-Meta: 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 DDaV0EtP 5xgTPX0QiVaGBs2+zD/vEIacaZT0Vc9a7RQTIdSMdYlkDhaiQiCi33WwAgJMHTDGrLERjloWnE1fqLKazG3v38dBSCFdlJO7swfGsz3YFcgVqfa6VvRcgPIsr1Q== 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 Thu, May 18, 2023 at 01:03:28PM -0700, Song Liu wrote: > If we use compound_order(), we will round up to power of 2 for all > allocations. Does this mean we will use 4MiB for a 2.1MiB allocation? Yes. This means we lose on average 33% - I believe, someone with better statistics might correct me - to internal fragmentation. But the buddy allocator will be better at avoiding and dealing with external fragmentation over time.