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Received: from willy by casper.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1u46d2-00000007Nln-2DQd; Sun, 13 Apr 2025 23:20:44 +0000 Date: Mon, 14 Apr 2025 00:20:44 +0100 From: Matthew Wilcox To: Barry Song <21cnbao@gmail.com> Cc: gaoxu , Mike Rapoport , Andrew Morton , "surenb@google.com" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , yipengxiang Subject: Re: [PATCH] mm: simplify zone_idx() Message-ID: References: <2d42decac5194c2c8d897b0424f0dcf3@honor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Stat-Signature: h8ri3pw5xgrfrc6ryztenjzdq58ecxzp X-Rspam-User: X-Rspamd-Queue-Id: D609F1C0006 X-Rspamd-Server: rspam08 X-HE-Tag: 1744586448-600516 X-HE-Meta: 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 I8/E/xz6 QvoXD6pB1+XBSI7ubE5SIocvgW32k+prqn2dsiugrdvC2a1gMjzJKd3FgzB1Dj+cH3jJX55WR5qYE9K1Oqh37/k7REyayixcdp8pT7CIjDHiBY9JHNR0NTQbMDBlvvwbUZLen22YYq9jE81DsLF41LRV4SuB6RjsGNbQUKsOYJ5Nfp3zU4gr62JZKYZdHMDuwbVSA8ox3le1Ncrlm0G6cqwaFE0AF/jlRSZl2pCj18jNIcQZalRDtxcBd4d6QYL+SQVSKl9+c1f+paGJQvoBhygO3TvHLsOcGfHZLdcCDNrMko2/OBKYrI8qYHx8HIgnynLHwqFv2gOOnOHGZ+V1bgZBLebXWzJsAFsralc/Wq2EzpVQqeI7F2ChZtEB+haD7F/bGql2BwPXhKPxlOEHFEbfg7w== 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: List-Subscribe: List-Unsubscribe: On Mon, Apr 14, 2025 at 09:57:26AM +1200, Barry Song wrote: > On Sat, Apr 12, 2025 at 10:06 PM gaoxu wrote: > > The zone info obtained through T32 in the Android 15-6.6 system(arm64): > > (struct zone) struct (1664 bytes, > > I don't have a strong opinion on whether we need `zone_idx`—I'm okay > with having it or not. If you'd like to add it, feel free to send out > a v2 noting that it doesn't increase the struct size. If no one > objects, it might be a nice cleanup. Plus it's already 1664 bytes! And we have, what, 4 zones per NUMA node? Growing it doesn't feel like a big deal. Although "saves two assembly instructions" is also not exactly a big win. If it saved a cacheline reference, that might be more interesting, but it seems like it's more likely to introduce a cacheline reference than save one. Maybe just not worth doing?