From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from [195.159.176.226] ([195.159.176.226]:35983 "EHLO blaine.gmane.org" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750891AbeD2Iab (ORCPT ); Sun, 29 Apr 2018 04:30:31 -0400 Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1fChgt-0005YP-1N for linux-btrfs@vger.kernel.org; Sun, 29 Apr 2018 10:28:15 +0200 To: linux-btrfs@vger.kernel.org From: Duncan <1i5t5.duncan@cox.net> Subject: Re: NVMe SSD + compression - benchmarking Date: Sun, 29 Apr 2018 08:28:09 +0000 (UTC) Message-ID: References: <5be6d7f3-c905-dc7b-56e0-4c4be60ea952@swiftspirit.co.za> <6adcb5da-16af-5453-383b-f289e9857506@swiftspirit.co.za> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: Brendan Hide posted on Sat, 28 Apr 2018 09:30:30 +0200 as excerpted: > My real worry is that I'm currently reading at 2.79GB/s (see result > above and below) without compression when my hardware *should* limit it > to 2.0GB/s. This tells me either `sync` is not working or my benchmark > method is flawed. No answer but a couple additional questions/suggestions: * Tarfile: Just to be sure, you're using an uncompressed tarfile, not a (compressed tarfile) tgz/tbz2/etc, correct? * How does hdparm -t and -T compare? That's read-only and bypasses the filesystem, so it should at least give you something to compare the 2.79 GB/s to, both from-raw-device (-t) and cached/memory-only (-T). See the hdparm (8) manpage for the details. * And of course try the compressed tarball too, since it should be easy enough and should give you compressable vs. uncompressable numbers for sanity checking. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman