From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-203.mta1.migadu.com [95.215.58.203]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 15A21356779 for ; Tue, 25 Aug 2026 22:06:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.203 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787695592; cv=none; b=qFCkyD9JCQRvJZsImUk0Ogf57VVtOTk3MkuIoBLjFdvcL58JA/k1UYPWbAc18p4ICBlB8FxCSUwnAqC8gqvHOkt2MjqUZ+5jdEfvSPlWCVqlGGjP1aj1wrcYP05a/Si8XxpYPhM9I3fh8gO6nLAHrpP20eVwoScesAlJY0YD1X0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787695592; c=relaxed/simple; bh=gFBOFMo679ZDXmdW0dMMgBbOdsuuqwAEoQO4bDPF8do=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=DEbfZr1DPOkvR850fTSoeHSzz2CRi1sO8RsP7kTaU62iiaf8XV5pBxpza/2c4rYyzRiP2RZbw5kYZSnMnw4qciPEB+FGUrEZEE7ffhU/CKXlAG5Fhkii9iR4zMKfq9481C0P8sXvwfDIBEWeObPSHjFvLZlRC58Y+xuvZ6qEMm0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=nfmQC8tq; arc=none smtp.client-ip=95.215.58.203 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="nfmQC8tq" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=gFBOFMo679ZDXmdW0dMMgBbOdsuuqwAEoQO4bDPF8do=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1787695589; v=1; x=1788300389; b=nfmQC8tqSbZRfJlTGNBMdNilQNBTHigvnmYPFFK/sEIp6O92cpifLk/nGfkfaONNYDwnh2TM h+zzZ5BxItsY7nOwG2FtYhhisX9HXCuzjcApuo/Eo5AEOmh/Ilyk5910ML59Yegj1GdwHTK2eY5 6POSxxO3VSg7MLIQi7PFUnXg= X-Envelope-To: linux-kernel@vger.kernel.org Received: from localhost (2a03:2880:10ff:59::) by mta10.migadu.com with ESMTPS id 6a51ded681de72a3; Tue, 25 Aug 2026 22:06:19 +0000 X-Mizu-Trace-ID: 6a51ded681de72a3 X-Migadu-Flow: FLOW_OUT From: Usama Arif To: davem@davemloft.net, dsterba@suse.com, Herbert Xu , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org, terrelln@fb.com Cc: hannes@cmpxchg.org, yosry@kernel.org, nphamcs@gmail.com, chengming.zhou@linux.dev, shakeel.butt@linux.dev, kernel-team@meta.com, Usama Arif Subject: [PATCH 0/2] crypto: zstd - avoid initializing the workspace twice Date: Tue, 25 Aug 2026 15:06:00 -0700 Message-ID: <20260825220616.3842633-1-usama.arif@linux.dev> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Both zstd_compress() and zstd_decompress() set up the shared per-CPU workspace as a C/DStream before walking the request, and then, when the first source and destination fragments each span the whole request, hand off to zstd_compress_one()/zstd_decompress_one(), which immediately overwrite that same ctx->wksp with a CCtx/DCtx. The stream setup is discarded without a byte having been processed. That one-shot path is not a corner case: zswap always takes it when storing, and takes it for a load whenever the stored object lies within a single zsmalloc page. These two patches defer the stream initialization to the first walk iteration that actually streams, guarded by a flag because that iteration can be reached more than once. A 4 KiB crypto_acomp benchmark [1], twelve runs of nine 30,000-operation rounds. Bare metal is an Intel Xeon Platinum 8321HC, turbo off, performance governor, pinned to one core; the VM is a one-vCPU KVM guest on a faster host. baseline patched delta bare metal compress 52,283 ns 51,038 ns 1,245 ns 2.4% decompress 2,317 ns 1,998 ns 319 ns 13.8% one-vCPU KVM compress 16,675 ns 15,050 ns 1,625 ns 9.8% decompress 3,516 ns 2,265 ns 1,251 ns 35.6% The guest numbers are larger because the two CPUID instructions in ZSTD_cpuid() become unconditional VM exits there. [1] https://gist.github.com/uarif1/5cf02f0e22c23f0d1b3d84348f12914c Usama Arif (2): crypto: zstd - Avoid redundant cstream initialization crypto: zstd - Avoid redundant dstream initialization crypto/zstd.c | 40 ++++++++++++++++++++++++++++------------ 1 file changed, 28 insertions(+), 12 deletions(-) base-commit: 4b18edbd8e70f7e6860d56370f13244896d0f95c -- 2.53.0-Meta