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[209.85.128.47]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b935ac73a5dsm378095766b.25.2026.03.01.10.58.36 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 01 Mar 2026 10:58:36 -0800 (PST) Received: by mail-wm1-f47.google.com with SMTP id 5b1f17b1804b1-48371bb515eso56367405e9.1 for ; Sun, 01 Mar 2026 10:58:36 -0800 (PST) X-Forwarded-Encrypted: i=1; AJvYcCXKOZJluR1xsHWkmDStbYc5zDIFrVB1iDE1DB6dxeyNBvx4irX2ObvlwGBZBdXz3K2ES2ad6XhavA==@kvack.org X-Received: by 2002:a17:907:a01:b0:b87:1741:a484 with SMTP id a640c23a62f3a-b93765630c3mr683986366b.43.1772391194481; Sun, 01 Mar 2026 10:53:14 -0800 (PST) MIME-Version: 1.0 References: <20260228141941.f6fec687aae9d80a161387f4@linux-foundation.org> In-Reply-To: From: Linus Torvalds Date: Sun, 1 Mar 2026 10:52:57 -0800 X-Gmail-Original-Message-ID: X-Gm-Features: AaiRm53wUk-j7BSu1BHekZwDQRwk7QegjDnqY-vnwFgpDSOB5GFu8_5dX2_z9CU Message-ID: Subject: Re: [PATCH 0/1] mm: improve folio refcount scalability To: Andrew Morton Cc: Gladyshev Ilya , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Zi Yan , Harry Yoo , Matthew Wilcox , Yu Zhao , Baolin Wang , Alistair Popple , Gorbunov Ivan , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Kiryl Shutsemau , Dave Chinner Content-Type: multipart/mixed; boundary="0000000000008d2745064bfafb4a" X-Rspam-User: X-Stat-Signature: ooek885iywaq5s6zmi3r5c9r6gynq17z X-Rspamd-Queue-Id: 5E430100003 X-Rspamd-Server: rspam03 X-HE-Tag: 1772391519-59717 X-HE-Meta: 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 rsbAUAAn QypXnPLq125XUzTsx5KQxgV2ZvDvacrBZhilqzJ+7N8QmKapu9B81zkkNi1T/hc0r2B6UESAB00LlWNu1GI8PBoOXShm8dkzJeeQrL16/ttIucixkn9cbclFpIkwgoriC8AAafEWM/Flx/D7qEMbwQihGJilbPJIUJBYBH/lIpxE3Aqav2VvdDjU+Yw7TZHUd/2YS9WctegyFixkLZHFvUZj3wyFnt7WuD5OWOtK6e1k8YZOG8WerLPVWAVav4vjxmPMFcXM+m/4XeC/RKU6mWW5qEmsmKaojCzaT5piuJouxdF9LAmqs8hL3PTnKGowZt0M7qfDn0Rw4sAbCFgItim1tThLLSHpwUW9FaV9Kefu+QttB8SeoD/iwo8KEYGlGpPDp6gIzSynacB3b5W/mpYgamW2v+KcRWGB+PrvyfwqKM8dbiBzn6Xb2rYyr7t5EqC+Ze9lI9W5bkHTtjR1yDoqP77JK/jRlZeECbT1DGBDcTZ7ggM8Ma/v+rNA6vw+QVdDz7BOODFLibUMUjAy2M7V+iExS7zOUhYy3+tz7flpnZv9WmF33zKPPRW1jYI/DBnf6cDYdAspT/5MPW2LLM8mXnY/z/KhizM6GSw5T00ervmBgkrHQwKW55A== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: --0000000000008d2745064bfafb4a Content-Type: text/plain; charset="UTF-8" On Sat, 28 Feb 2026 at 19:27, Linus Torvalds wrote: > > This attached patch is ENTIRELY UNTESTED. Here's a slightly cleaned up and further simplified version, which is also actually tested, although only in the "it boots for me" sense. It generates good code at least with clang: .LBB76_7: movl $1, %eax .LBB76_8: leal 1(%rax), %ecx lock cmpxchgl %ecx, 52(%rdi) sete %cl je .LBB76_10 testl %eax, %eax jne .LBB76_8 .LBB76_10: which actually looks both simple and fairly optimal for that sequence. Of course, since this is very much about cacheline access patterns, actual performance will depend on random microarchitectural issues (and not just the CPU core, but the whole memory subsystem). Can somebody with a good - and relevant - benchmark system try this out? Linus --0000000000008d2745064bfafb4a Content-Type: text/x-patch; charset="US-ASCII"; name="patch.diff" Content-Disposition: attachment; filename="patch.diff" Content-Transfer-Encoding: base64 Content-ID: X-Attachment-Id: f_mm83pnxn0 IGluY2x1ZGUvbGludXgvcGFnZV9yZWYuaCB8IDExICsrKysrKysrKy0tCiAxIGZpbGUgY2hhbmdl ZCwgOSBpbnNlcnRpb25zKCspLCAyIGRlbGV0aW9ucygtKQoKZGlmZiAtLWdpdCBhL2luY2x1ZGUv bGludXgvcGFnZV9yZWYuaCBiL2luY2x1ZGUvbGludXgvcGFnZV9yZWYuaAppbmRleCA1NDQxNTBk MWQ1ZmQuLmQ4ZTRmMTc1Zjc0YyAxMDA2NDQKLS0tIGEvaW5jbHVkZS9saW51eC9wYWdlX3JlZi5o CisrKyBiL2luY2x1ZGUvbGludXgvcGFnZV9yZWYuaApAQCAtMjM0LDggKzIzNCwxNSBAQCBzdGF0 aWMgaW5saW5lIGJvb2wgcGFnZV9yZWZfYWRkX3VubGVzcyhzdHJ1Y3QgcGFnZSAqcGFnZSwgaW50 IG5yLCBpbnQgdSkKIAogCXJjdV9yZWFkX2xvY2soKTsKIAkvKiBhdm9pZCB3cml0aW5nIHRvIHRo ZSB2bWVtbWFwIGFyZWEgYmVpbmcgcmVtYXBwZWQgKi8KLQlpZiAocGFnZV9jb3VudF93cml0YWJs ZShwYWdlLCB1KSkKLQkJcmV0ID0gYXRvbWljX2FkZF91bmxlc3MoJnBhZ2UtPl9yZWZjb3VudCwg bnIsIHUpOworCWlmIChwYWdlX2NvdW50X3dyaXRhYmxlKHBhZ2UsIHUpKSB7CisJCS8qIEFzc3Vt ZSBjb3VudCA9PSAxLCBkb24ndCByZWFkIGl0ISAqLworCQlpbnQgb2xkID0gMTsKKwkJZG8gewor CQkJcmV0ID0gYXRvbWljX3RyeV9jbXB4Y2hnKCZwYWdlLT5fcmVmY291bnQsICZvbGQsIG9sZCsx KTsKKwkJCWlmIChsaWtlbHkocmV0KSkKKwkJCQlicmVhazsKKwkJfSB3aGlsZSAob2xkKTsKKwl9 CiAJcmN1X3JlYWRfdW5sb2NrKCk7CiAKIAlpZiAocGFnZV9yZWZfdHJhY2Vwb2ludF9hY3RpdmUo cGFnZV9yZWZfbW9kX3VubGVzcykpCg== --0000000000008d2745064bfafb4a--