From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 392B2C4320A for ; Wed, 4 Aug 2021 13:37:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11EFA60F41 for ; Wed, 4 Aug 2021 13:37:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237384AbhHDNiE (ORCPT ); Wed, 4 Aug 2021 09:38:04 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:44522 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234089AbhHDNiE (ORCPT ); Wed, 4 Aug 2021 09:38:04 -0400 Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id CBEC91FDF1; Wed, 4 Aug 2021 13:37:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1628084270; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kAOyPfhApQEvYuznvyJ9FA5mKKOF/pnqDMA2tFhz0QM=; b=QI3YyHqfmDJGAdQgLFOU+rlhZPyk3YS7dLYnRBSb+B751BIzkRHfZowKoCuN2VcJEqhr7i /3ew01zSCO8Gbf0scwI/WkYkM2CZMorCEoth7qVPG4NX7sRhdB61h1ETsaKGFSXnc7zFmB a/xsfNqKc9utPqgY+rfk7WXnf5XQWSM= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1628084270; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kAOyPfhApQEvYuznvyJ9FA5mKKOF/pnqDMA2tFhz0QM=; b=V3EG5c72wjKqApkkkYjmPcIo2GiCxgGiOeL12dG1KvMZYgpMAaCVMhZQ0yOHFyWZNAUSDH nVK5N3hbGXkl2UBg== Received: from imap1.suse-dmz.suse.de (imap1.suse-dmz.suse.de [192.168.254.73]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap1.suse-dmz.suse.de (Postfix) with ESMTPS id A26C513942; Wed, 4 Aug 2021 13:37:50 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id mkY1Ji6YCmEPQAAAGKfGzw (envelope-from ); Wed, 04 Aug 2021 13:37:50 +0000 Date: Wed, 4 Aug 2021 15:37:49 +0200 From: David Disseldorp To: Al Viro Cc: linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, Matthew Wilcox Subject: Re: [PATCH RESEND 1/3] initramfs: move unnecessary memcmp from hot path Message-ID: <20210804153749.5bb69afd@suse.de> In-Reply-To: References: <20210721115153.28620-1-ddiss@suse.de> <20210804113129.60848be6@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, 4 Aug 2021 12:57:16 +0000, Al Viro wrote: > On Wed, Aug 04, 2021 at 11:31:29AM +0200, David Disseldorp wrote: > > Ping, any feedback on this change? > > > > I think it's a no brainer, but for kicks I ran a few unrealistic micro > > benchmarks on my laptop. Extraction time for a cpio image with 1M+ > > directories improved by 5ms (pre: 14.614s, post: 14.609s), when averaged > > across 20 runs of: > > qemu-system-x86_64 -machine accel=kvm -smp cpus=1 -m 10240 \ > > -kernel ~/linux/arch/x86/boot/bzImage \ > > -initrd ./initrds/gen_cpio.out \ > > -append "initramfs_async=0 console=ttyS0 panic=0" -nographic \ > > | awk '/Trying to unpack rootfs/ {start_ts = $2}; > > /Freeing initrd memory/ {end_ts = $2} > > END {printf "%f\n", end_ts - start_ts}' > > What was the dispersion for those runs? Too high for the 5ms to be considered statistically significant. Std deviations were pre: 171ms, post: 214ms... I'll redo this on a proper test rig. Cheers, David