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[209.85.128.46]) by smtp.gmail.com with ESMTPSA id a23-20020aa7d757000000b0042617ba6393sm7799283eds.29.2022.05.10.10.28.44 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 May 2022 10:28:45 -0700 (PDT) Received: by mail-wm1-f46.google.com with SMTP id bg25so10608274wmb.4 for ; Tue, 10 May 2022 10:28:44 -0700 (PDT) X-Received: by 2002:a05:600c:4f06:b0:394:836b:1552 with SMTP id l6-20020a05600c4f0600b00394836b1552mr998628wmq.145.1652203724417; Tue, 10 May 2022 10:28:44 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Tue, 10 May 2022 10:28:28 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: clear_user (was: [patch 02/14] tmpfs: fix regressions from wider use of ZERO_PAGE) To: Borislav Petkov Cc: Mark Hemment , Andrew Morton , "the arch/x86 maintainers" , Peter Zijlstra , patrice.chotard@foss.st.com, Mikulas Patocka , Lukas Czerner , Christoph Hellwig , "Darrick J. Wong" , Chuck Lever , Hugh Dickins , patches@lists.linux.dev, Linux-MM , mm-commits@vger.kernel.org, Mel Gorman Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: B721320099 X-Stat-Signature: 8cume1gqju5p8gedxm3xhj4xw6ij3sbg Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b="eft9x/Ew"; spf=pass (imf31.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.218.41 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-HE-Tag: 1652203706-244777 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 Tue, May 10, 2022 at 2:31 AM Borislav Petkov wrote: > > clear_user_original: > Amean: 9219.71 (Sum: 6340154910, samples: 687674) > > fsrm: > Amean: 8030.63 (Sum: 5522277720, samples: 687652) Well, that's pretty conclusive. I'm obviously very happy with fsrm. I've been pushing for that thing for probably over two decades by now, because I absolutely detest uarch optimizations for memset/memcpy that can never be done well in software anyway (because it depends not just on cache organization, but on cache sizes and dynamic cache hit/miss behavior of the load). And one of the things I always wanted to do was to just have memcpy/memset entirely inlined. In fact, if you go back to the 0.01 linux kernel sources, you'll see that they only compile with my bastardized version of gcc-1.40, because I made the compiler inline those things with 'rep movs/stos', and there was no other implementation of memcpy/memset at all. That was a bit optimistic at the time, but here we are, 30+ years later and it is finally looking possible, at least on some uarchs. Linus