From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=202.12.124.151 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792487222; b=1oZMKUj/fDAgxjZFY1DTrP6DEZb3018T60YNVOlEb+rU+C+fRFomlNEgrKpK82I1kTR4 5rkNqwzb2PFgpzSJT/JJyyfSWW9EOrM4tbWqOqJJ8SyiCphX4cxgKr/K19YREyfeoPKBo Y5lYrLZk7lnVknD20/DSt4C3ZzT3+KWgu9DzJndxTA0dmo0yqGkBA4yJG0VCTQBVnV35N jKqLs7ZE8pNyyR/jMHEgtHWI+xVr1ZXcupNkRGAA0I+fAfo/iSFJskNITkJhKmLuOnTKS K55YZguH7VR3lmbP9XBu0za9HBYBg9JwFMaCZ6PVsL9mL0WnPYK9+n/vjxuXy6KsZVQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792487222; h=DMARC-Filter:Received:Received:DKIM-Signature:DKIM-Signature: X-DKIM2-Info:DKIM2-Signature:X-DKIM2-Info:Message-Instance: X-ME-Sender:X-ME-Proxy-Cause:X-ME-Proxy:Feedback-ID:Received:X-Mailer: MIME-Version:X-ThreadId:Date:From:To:Cc:Message-Id:In-Reply-To: References:Subject:Content-Type:Content-Transfer-Encoding; bh=qbtBT1zpSxLsbcMbyYVhf3JDYC/W4xf5mt5D10gHvo0=; b=dVrOzC7pcn2aqKZgzaLSL76+C/smXZBWvbn6j7K33kRMpj8sFxarxkya7bPrwHYy7m4v roDZfaD7gxfbwJamCpEn1BUvKNV0/liwK/pliJ+6gqnWNckWxGqAA/U5AIj8z1ShYai6V WT+mGz644KXtsz0Zuu04JljP8DXroyQ0kM+ZMM75ZNMm3EiwCEl+PPxHZ3i5CLkZEJHoq FJVg9HIQGhNa/96721VoEz3pMAeoAaJwexFGflgyuDvHEcM1l88jGEH0fitTlI3n74qTd lVsLuNfUVGu65FVv3fupZmeKObu/hP9NUdnnh/xaCgxvnSMEif6WY4/fUOuPLWPHssg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=arndb.de; spf=pass smtp.mailfrom=arndb.de; dkim=pass header.d=arndb.de header.i=@arndb.de header.a=rsa-sha256 header.s=fm1 header.b=YAgmFXmj; dkim=pass header.d=messagingengine.com header.i=@messagingengine.com header.a=rsa-sha256 header.s=fm2 header.b=Vdjp2tjY; arc=none smtp.remote-ip=202.12.124.151 Received: from fout-b8-smtp.messagingengine.com (fout-b8-smtp.messagingengine.com [202.12.124.151]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6A0BA606A31C for ; Tue, 20 Oct 2026 09:07:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 6A0BA606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arndb.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arndb.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=arndb.de header.i=@arndb.de header.a=rsa-sha256 header.s=fm1 header.b=YAgmFXmj; dkim=pass (2048-bit key, unprotected) header.d=messagingengine.com header.i=@messagingengine.com header.a=rsa-sha256 header.s=fm2 header.b=Vdjp2tjY Received: from ams-compute-02.internal (ams-compute-02.internal [10.64.2.62]) by mailfout.stl.internal (Postfix) with ESMTP id 762061D00043 for ; Tue, 20 Oct 2026 05:07:01 -0400 (EDT) Received: from ams-imap-03 ([10.64.2.23]) by ams-compute-02.internal (MEProxy); Tue, 20 Oct 2026 05:07:01 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arndb.de; h=cc :cc:content-transfer-encoding:content-type:content-type:date :date:from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to; s=fm1; t=1792487213; x=1792573613; bh=qbtBT1zpSxLsbcMbyYVhf3JDYC/W4xf5mt5D10gHvo0=; b= YAgmFXmjB9LJCqu5UhfWhrgkMQ+78wWrQqA2QRxxmQ9mmdJLYKjVExsXPcIQ1nCY HYO0VQW8oNhgA78fDNH9KiQwpz85a4KLmWQcxjENLDhNNFKaWVTlrH6JqKhVZxjN 3ayzQ+9YE2HyrkD2JbMfaAOOsgfxFQheg8Yr56I4HrD3FQb8nydfmBJjHSc9WLH+ rH5SOKG+M2XhFzmE0+Ah59kMDRtPzHItkPXQ63e0SN2z3TANvWi+jN/1E2dmDXLj YdoQzjMWcbmNMNLIAk4Erj05hkXqVezobDhOHEOnPxn+EkjpbZY9awVsB3a2zmX+ hX1W5EDi23GiFOXKV9UGmw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=cc:cc:content-transfer-encoding :content-type:content-type:date:date:feedback-id:feedback-id :from:from:in-reply-to:in-reply-to:message-id:mime-version :references:reply-to:subject:subject:to:to:x-me-proxy :x-me-sender:x-me-sender:x-sasl-enc; s=fm2; t=1792487213; x= 1792573613; bh=qbtBT1zpSxLsbcMbyYVhf3JDYC/W4xf5mt5D10gHvo0=; b=V djp2tjYjltPD9WauoYY13RPgdVY2L88pxKoNitXC4D+yzKb20SlGcgQlumZ+iSSs w9PoA4x4okUEJqt7BkhuhkHhMGhAoamuvH4xLGNYNFOAB0baTFjUmqzyO0ZoaTDZ o7MZb8yO3DpsVrQcw0g202eYqvjCqPn5rXdvnNPHS3dYjgnthyF3ddnLNAN/mC08 X5W1Fe4fKVkWyw9WoNuR54h6fULRnD+ZaN7zLV99fohkG5vu5ckL74K/UzRJVEj8 AyRUZl13q7NmSTU8enZ9nQ6yQiJsv+9FQvcuXq/iztp66w2og2JWwO7ERo7bwx0H OMS1QMQBLoMZFeBHGHwnQ== X-DKIM2-Info: draft=ietf-dkim-dkim2-spec-06; repo=github.com/dkim2wg/interop; date=2026-10-08; sw=lmtpprox; action=sign d=arndb.de a=rsa-sha256; DKIM2-Signature: i=1; m=1; t=1792487213; d=arndb.de; mf=PGFybmRAYXJuZGIuZGU+; rt=PGxpbnV4LWtlcm5lbEB2Z2VyLmtlcm5lbC5vcmc+; s=fm1:rsa-sha256:eAEok5Kxwn7zz9xiB4598w6G2D5sXY148xP053llKN4mQwh 1SaGuRotGWf75dFXUKHNWzI9wdKtmHjHMMVhCI4ZrWT6YZvUH3h/6jsyZoDXNbOD NbjYuZT1WQQ6xXkRAgkSDm0N/o+nkHmbfGD6NgApl+AJxu1L6pvec24ZjoG0L/1o 0H4USEwyWxHDNrCLvO7Shoh/ZD9lMPNGlbm2BobKFkFcp/i0I7bCUJkGS9Rono4K UduN2ZmYMBj8AWehKOi9tweTWp/sxBQ60FvKoBebZuFg3i4jo5eG5x7RP6UvGh4c oD/RniKDTsu2243XsjG9D4NNIQOFHAat06Qydqg==; X-DKIM2-Info: draft=ietf-dkim-dkim2-spec-06; repo=github.com/dkim2wg/interop; date=2026-10-08; sw=lmtpprox; action=mi-m=1; hc=12; hn=cc,content-transfer-encoding,content-type,date,feedback-id, from,in-reply-to,message-id,mime-version,references,subject,to; Message-Instance: m=1; h=sha256:Zf6XtnsRdLogxNdsFsiNl9U5lteyoRFbzV8KFT94ceY=:P1+4NKlddnjAdfdPKXMMf1nmswzQ3j+bprK9cbCihoY=; X-ME-Sender: X-ME-Proxy-Cause: dmFkZTE6pYZjwqD9MuJZc6oGG5G4d8tXnhSRk+nCvHZBTrmX1lvtdBB2z4mSt0mtErSvno uKHAQgvOcedGlRXGN7ggqvLURejOEB3vEgubbBGVASzH5JJGm6qRIN7+Gu8ohdrqvGK08J 9BbwSughj3UMjk4bVE1QdUhNjKK7NLUIqJUN5sOIHEt5TldzHgx1WzzQ4L7xS7cooChcY7 rv9AuZIKyXllIY9hKA8K1G8fT7AhYuwJ6qGIBKV8AnLHrcr1onLXuEYAENhM6M9GpdYJdV vkCe5+12oZhdEE/U4lNHMtLhbLVabIlgzVVGYs6J/gKl8M51RVdHoeS/WfEqq9dzde8cNA eNHfYge7WVbCoY1+KLuQFPAMWOF66HrRo+3NmsOZYMQ8MlJPXBpLhIW/NYglbhGmndf001 A/6CMGeBVygqyslGZMOveGymtrbbq+TtoAE/SJdXKT1O/6B+CIsxWx5kQzJAhUh3o3S+ya ED2Cy9rqkUtvjKWQYuULfth6786qsr9yRxVAWVY1kxTZGxiLaoGHBG0CuazaMdF8V4RGTy Kvq2LFyyqME+xXjn42vkYOKvHkXbnS/HPrkOtI5grRs9rvhzIwVtVyB/u/3b+cDvGF++rC V984mXo98wkevu6m2MU40qe1fO2ZJ+FRXK6bm1CfEyG+jjKniYAIhuMEKouw X-ME-Proxy: Feedback-ID: i56a14606:Fastmail Received: by mailuser.ams.internal (Postfix, from userid 501) id 506CA32A008F; Tue, 20 Oct 2026 05:06:48 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-ThreadId: ATLhSvAouVZo Date: Tue, 20 Oct 2026 11:06:06 +0200 From: "Arnd Bergmann" To: "Marc Kleine-Budde" Cc: "Ian Rogers" , "Thomas Gleixner" , "Andy Lutomirski" , "Vincenzo Frascino" , "Stefan Kerkmann" , "Christophe Leroy" , "David Laight" , "Arnaldo Carvalho de Melo" , "Namhyung Kim" , "Eric Biggers" , "Alexander Viro" , "Jason A . Donenfeld" , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Message-Id: In-Reply-To: <20261020-zealous-warping-quetzal-84479a-mkl@pengutronix.de> References: <20261019201257.3805356-1-irogers@google.com> <31fe09f6-0a14-40fc-8ad8-c03998fb1f5c@app.fastmail.com> <20261020-succinct-zebu-of-vigor-6cb2cd-mkl@pengutronix.de> <20261020-zealous-warping-quetzal-84479a-mkl@pengutronix.de> Subject: Re: [PATCH v1 1/2] vdso: Add VDSO_UNALIGNED_PACKED config option for ARMv5 Content-Type: text/plain Content-Transfer-Encoding: 7bit On Tue, Oct 20, 2026, at 10:41, Marc Kleine-Budde wrote: > On 20.10.2026 10:24:51, Arnd Bergmann wrote: >> On Tue, Oct 20, 2026, at 08:44, Marc Kleine-Budde wrote: >> >> That would be better, but I still hope we can just get back to the >> portable code across all architectures for the in-kernel version. >> >> I have one more request for you: can you check /proc/cpu/alignment >> on the system that shows the performance regression with and without >> the patch? > > I asked Stefan Kerkmann (who wrote the original regression report) the > same question, but we haven't had time for it yet. We'll get around to > it. Ok, thanks! >> In your original report, you have shown that Ian's patch >> caused the drop in performance and that it caused the added function >> calls, but I don't see any sufficiently hot code path that would >> actually explain the scale of the regression, > > Don't underestimate the overhead of function calls on those old CPUs > with tiny I-caches. What I meant is that I tried to look for calls to get_unaligned() in the code path you'd hit with UBIFS on nand flash, and I only found a possible call once per page written (ebu_nand_write_page_hwecc), which should have a much lower overhead than what you observe. While ubifs does use crc32, it uses the lib/crc/ version rather than the crypto/crc32c.c that you listed, and there is no get_unaligned() in the lib/ one. If you have NOR flash, the caller is likely do_write_buffer() calling map_word_load(). That one could explain the problem and could also be optimized further if it turns out to be the bottleneck. Arnd