From nobody Tue Dec 14 04:42:08 2021 X-Original-To: freebsd-hackers@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 700FB18D6BEB for ; Tue, 14 Dec 2021 04:42:11 +0000 (UTC) (envelope-from sblachmann@gmail.com) Received: from mail-lf1-x131.google.com (mail-lf1-x131.google.com [IPv6:2a00:1450:4864:20::131]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "smtp.gmail.com", Issuer "GTS CA 1D4" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4JCm1v2VKLz3smM; Tue, 14 Dec 2021 04:42:11 +0000 (UTC) (envelope-from sblachmann@gmail.com) Received: by mail-lf1-x131.google.com with SMTP id m27so34683753lfj.12; Mon, 13 Dec 2021 20:42:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=chMqm45m6qJ7f24JuuQYh39wn6STlWndviL1XADDdzE=; b=DltKYxDB5RGQkCxKo8oo3aWxspJte2/ihmwY+kgzwIp28Hc4oJ9iNdh5A7w1z0uJ7t BCOiaqhTfU9Ii86CSstcMQ8Ls6PsCMYbNCxi95CGcRYHxDlDyGs/EZokx4KcExYgBBMp 7JY6rklzzWkjuWHvoRy1ud2cu9W4VMgB2378KJ2r3u8VCX8nt8ErTpZZMlJeO3k9e08i AXrIODivJbLa5AzwSlNkFIJ0I4ACKV651WVz6mMGOeggdVhHYtbvmENIiLtEMAe7+UHU 8xmLKpVXAhzx+SlkjXv/ZA0TJyOapGckkaGidRW6Ov/oN1RnNfGojEDmO1dfFudonf96 5ESg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=chMqm45m6qJ7f24JuuQYh39wn6STlWndviL1XADDdzE=; b=fbUSbD+tlnmUmOT+YYTZW4j48b5j1WFGmWGG7rUymdisV3HyO9UTk4ZkEI6BKHFKot ymwnWpVukwrkFuzQYFce2iLYl3s7wgLkDByMUzBW//GRtITKyyh+a5wDcyx0L8vG7NWq 9nrBpadjrCc6q3Vlm9x7MTfMuLcrgxsYSt578RLUbZsVSv+ps/BJH7ig3kLWm0lLHPDc Nz2zFPGtfYcGKXN5kPnQvlQ0EcMp26pbH4a0w/rt8z30bh7CV9zF0Ibuc/QzrKIu12LW DMO0UoS6qUCBgi/40q2h77LnXFrSYd42FIjrLajBp6RAe2LCkhLnsG7hnSTo3TUFtEyW 00MQ== X-Gm-Message-State: AOAM532VDOK1QD8Cz1mgwKGh0D5YXXH3S7VX6gkLWzazWJwg1VFgO0IH Z0GuCcC5a/V7haEsHvNF3ZpDZ4sp7KJqvnlp2Zc= X-Google-Smtp-Source: ABdhPJyJmeh5tp//+sTVQSFC7JvqaKVWKzwycvo9rhf+cDFcQL8PCiYBAWfGJ7Fi4KeDkVoPntk3X7F6Entep6LrJB8= X-Received: by 2002:a05:6512:3718:: with SMTP id z24mr2654753lfr.563.1639456929006; Mon, 13 Dec 2021 20:42:09 -0800 (PST) List-Id: Technical discussions relating to FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-hackers List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-hackers@freebsd.org MIME-Version: 1.0 Received: by 2002:a05:651c:1242:0:0:0:0 with HTTP; Mon, 13 Dec 2021 20:42:08 -0800 (PST) In-Reply-To: References: From: Stefan Blachmann Date: Tue, 14 Dec 2021 05:42:08 +0100 Message-ID: Subject: Re: Weak disk I/O performance on daX compared to adaX, was: Re: dd performance [was Re: Call for Foundation-supported Project Ideas] To: Warner Losh Cc: Alan Somers , Johannes Totz , FreeBSD Hackers Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 4JCm1v2VKLz3smM X-Spamd-Bar: ---- Authentication-Results: mx1.freebsd.org; none X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[] X-ThisMailContainsUnwantedMimeParts: N Hi Warner, thank you for the reply! > Because it isn't an ahci controller, but something else. dmesg will tell > you, or camcontrol devlist. It might be crappy hardware, poorly configured > or maybe you've discovered a driver bug that's easy to fix. There is a RAID BIOS on the HP Z420 that apparently cannot be deactivated. According to what the RAID BIOS screen displays, there is no RAID configured, and the drives connected to the system seem to be "passed through" to the OS. The camcontrol devlist output (see the two WD 2003FYYS): at scbus0 target 0 lun 0 (pass0,da0) at scbus0 target 1 lun 0 (pass1,da1) at scbus0 target 2 lun 0 (pass2,da2) at scbus0 target 3 lun 0 (pass3,da3) at scbus1 target 0 lun 0 (cd0,pass4) at scbus2 target 0 lun 0 (pass5,ada0) at scbus3 target 0 lun 0 (pass6,ses0) at scbus4 target 0 lun 0 (da4,pass7) The dmesg (not obviously disk-related stuff snipped) tells about a SATA controller and a SAS controller in SATA mode: isci0: port 0xd000-0xd 0ff mem 0xe2800000-0xe2803fff,0xe2400000-0xe27fffff irq 16 at device 0.0 on pci4 ahci0: port 0xe0d0-0xe0d7,0xe0c0-0xe0c3,0x e0b0-0xe0b7,0xe0a0-0xe0a3,0xe020-0xe03f mem 0xef72c000-0xef72c7ff irq 19 at devi ce 31.2 on pci0 ahci0: AHCI v1.30 with 6 6Gbps ports, Port Multiplier not supported ahcich0: at channel 0 on ahci0 ahcich1: at channel 1 on ahci0 ahciem0: on ahci0 ses0 at ahciem0 bus 0 scbus3 target 0 lun 0 ses0: SEMB S-E-S 2.00 device ses0: SEMB SES Device ada0 at ahcich1 bus 0 scbus2 target 0 lun 0 ada0: ATA8-ACS SATA 2.x device ada0: Serial Number WD-WMAY04325670 ada0: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes) ada0: Command Queueing enabled ada0: 1907729MB (3907029168 512 byte sectors) ses0: (none) in 'Slot 00', SATA Slot: scbus1 target 0 ses0: ada0 in 'Slot 01', SATA Slot: scbus2 target 0 da0 at isci0 bus 0 scbus0 target 0 lun 0 da0: Fixed Direct Access SPC-3 SCSI device da0: Serial Number 14260C786E76 da0: 300.000MB/s transfers da0: Command Queueing enabled da0: 244198MB (500118192 512 byte sectors) da1 at isci0 bus 0 scbus0 target 1 lun 0 da1: Fixed Direct Access SPC-3 SCSI device da1: Serial Number Z7747X6AS da1: 300.000MB/s transfers da1: Command Queueing enabled da1: 2861588MB (5860533168 512 byte sectors) da2 at isci0 bus 0 scbus0 target 2 lun 0 da2: Fixed Direct Access SPC-3 SCSI device da2: Serial Number Z7747SSAS da2: 300.000MB/s transfers da2: Command Queueing enabled da2: 2861588MB (5860533168 512 byte sectors) cd0 at ahcich0 bus 0 scbus1 target 0 lun 0 cd0: Removable CD-ROM SCSI device cd0: 150.000MB/s transfers (SATA 1.x, UDMA5, ATAPI 12bytes, PIO 8192bytes) cd0: Attempt to query device size failed: NOT READY, Medium not present - tray c losed da3 at isci0 bus 0 scbus0 target 3 lun 0 da3: Fixed Direct Access SPC-3 SCSI device da3: Serial Number WD-WMAY04325722 da3: 300.000MB/s transfers da3: Command Queueing enabled da3: 1907729MB (3907029168 512 byte sectors) GEOM_ELI: Device da0p2.eli created. GEOM_ELI: Encryption: AES-XTS 128 GEOM_ELI: Crypto: accelerated software System is only running dd, except for a few sc consoles idling at command prompt nothing else. top -m io varies 99.8 to 100% for dd top without options dd shows a time of >800:x for dd and a WCPU varying between 3.5-4.2%. For the drive on ada0 dd total time was ~150:x with a WCPU of ~1%. On 12/14/21, Warner Losh wrote: > On Mon, Dec 13, 2021 at 8:08 PM Stefan Blachmann > wrote: > >> I am wondering what could be the cause for the weak disk I/O >> performance on FreeBSD when using daX drivers instead of adaX drivers. >> >> Explanation: >> The HP Z420 has 6 SATA ports. >> SATA drives that get connected to port #1 to #4 are being shown as daX >> drives on FreeBSD. >> Drives connected to ports 5 and 6 appear as adaX drives. >> >> > On 12/2/21, Alan Somers wrote: >> >> That is your problem then. The default value for dd if 512B. If it >> >> took 3 days to erase a 2 TB HDD, that means you were writing 15,000 >> >> IOPs. Frankly, I'm impressed that the SATA bus could handle that >> >> This shows that on the ada driver, the disk I/O performance is >> acceptable. >> However, after 14 days dd is still working on the same type drive on >> connector 4 (da3). >> >> So my questions: >> - Why does FreeBSD use the da driver instead of the ada driver for >> drives on SATA ports 1-4? >> > > Because it isn't an ahci controller, but something else. dmesg will tell > you, or camcontrol devlist. It might be crappy hardware, poorly configured > or maybe you've discovered a driver bug that's easy to fix. > > >> - And, why is the da driver so slow? (For example, on HP Z800 when >> used with FreeBSD, 15k SAS drives seem as slow as normal consumer >> drives, while on Linux disk I/O is just snappy.) >> > > It isn't. It's more likely the controller they are attached to that's slow. > At work > we get line rate out of daX and adaX all the time. They are just protocol > translators and hands it off to the host adapter (what's called the SIM). > > >> - Is there a way to configure FreeBSD to use the ada driver instead of >> the da driver, so using FreeBSD is still an alternative to Linux if >> disk speed matters? >> > > Unlikely. > > >> - Or is it impossible to use the ada drivers on SATA connectors 1-4 >> for maybe some HP Z420 hardware related reasons? >> > > What does camcontrol devlist tell you? Chances are it's the SIM that's to > blame for the poor performance (we run all kinds of crazy I/O through ada > and da and if anything da is a smidge faster). The key question is why > things are so seemingly slow. > > Warner > > >> Cheers, >> Stefan >> >> >> On 12/2/21, Stefan Blachmann wrote: >> > Ah, the buffer cache! Didn't think of that. >> > Top shows the weighted cpu load is about 4%, so your guess that it was >> > the SATA scheduler might be correct. >> > Will try this on Linux the next days using conv=direct with a pair of >> > identical HDDs. >> > Already curious for the results. >> > >> > >> > >> > On 12/2/21, Alan Somers wrote: >> >> That is your problem then. The default value for dd if 512B. If it >> >> took 3 days to erase a 2 TB HDD, that means you were writing 15,000 >> >> IOPs. Frankly, I'm impressed that the SATA bus could handle that >> >> many. By using such a small block size, you were doing an excellent >> >> job of exercising the SATA bus and the HDD's host interface, but its >> >> servo and write head were mostly just idle. >> >> >> >> The reason why Linux is different is because unlike FreeBSD it has a >> >> buffer cache. Even though dd was writing with 512B blocks, those >> >> writes probably got combined by the buffer cache before going to SATA. >> >> However, if you use the conv=direct option with dd, then they probably >> >> won't be combined. I haven't tested this; it's just a guess. You can >> >> probably verify using iostat. >> >> >> >> When you were trying to erase two HDDs concurrently but only one was >> >> getting all of the IOPs and CPU time, was your CPU saturated? I'm >> >> guessing not. On my machine, with a similar HDD, dd only consumes 10% >> >> of the CPU when I write zeros with a 512B block size. I need to use a >> >> 16k block size or larger to get the IOPs under 10,000. So I'm >> >> guessing that in your case the CPU scheduler was working just fine, >> >> but the SATA bus was saturated, and the SATA scheduler was the source >> >> of the unfairness. >> >> -Alan >> >> >> >> On Thu, Dec 2, 2021 at 10:37 AM Stefan Blachmann >> >> >> >> wrote: >> >>> >> >>> I intentionally used dd without the bs parameter, as I do care less >> >>> about "maximum speed" than clearing the drives completely and also do >> >>> a lot of I/O transactions. >> >>> The latter because drives that are becoming unreliable tend to >> >>> occasionally throw errors, and the more I/O transactions one does the >> >>> better the chance is to spot this kind of drives. >> >>> >> >>> The system is a HP Z420, the mainboard/chipset/controller specs can >> >>> be >> >>> found in the web. >> >>> The drives in question here (quite old) 2TB WD Black enterprise grade >> >>> 3.5" SATA drives. Their SMART data is good, not hinting at any >> >>> problems. >> >>> >> >>> On Linux, erasing them both concurrently finished at almost the same >> >>> time. >> >>> Thus I do not really understand why on FreeBSD this is so much >> >>> different. >> >>> >> >>> On 12/2/21, Alan Somers wrote: >> >>> > This is very surprising to me. I never see dd take significant CPU >> >>> > consumption until the speed gets up into the GB/s range. What are >> you >> >>> > using for the bs= option? If you set that too low, or use the >> >>> > default, it will needlessly consume extra CPU and IOPs. I usually >> set >> >>> > it to 1m for this kind of usage. And what kind of HDDs are these, >> >>> > connected to what kind of controller? >> >>> > >> >>> > On Thu, Dec 2, 2021 at 9:54 AM Stefan Blachmann < >> sblachmann@gmail.com> >> >>> > wrote: >> >>> >> >> >>> >> Regarding the suggestions to either improve or replace the ULE >> >>> >> scheduler, I would like to share another observation. >> >>> >> >> >>> >> Usually when I need to zero out HDDs using dd, I use a live Linux. >> >>> >> This time I did that on FreeBSD (13). >> >>> >> My observations: >> >>> >> - On the same hardware, the data transfer rate is a small fraction >> >>> >> (about 1/4th) of which is achieved by Linux. >> >>> >> - The first dd process, which erases the first HDD, gets almost >> >>> >> all >> >>> >> CPU and I/O time. The second process which does the second HDD is >> >>> >> getting starved. It actually really starts only after the first >> >>> >> one >> >>> >> finished. >> >>> >> >> >>> >> To me it was *very* surprising to find out that, while erasing two >> >>> >> similar HDDs concurrently takes about one day on Linux, on >> >>> >> FreeBSD, >> >>> >> the first HDD was finished after three days, and only after that >> >>> >> the >> >>> >> remaining second dd process got the same CPU time, making it >> >>> >> proceed >> >>> >> fast instead of creepingly slowly. >> >>> >> >> >>> >> So I guess this might be a scheduler issue. >> >>> >> I certainly will do some tests using the old scheduler when I got >> >>> >> time. >> >>> >> And, I ask myself: >> >>> >> Could it be a good idea to sponsor porting the Dragonfly scheduler >> to >> >>> >> FreeBSD? >> >>> >> >> >>> >> On 12/2/21, Johannes Totz wrote: >> >>> >> > On 29/11/2021 03:17, Ed Maste wrote: >> >>> >> >> On Sun, 28 Nov 2021 at 19:37, Steve Kargl >> >>> >> >> wrote: >> >>> >> >>> >> >>> >> >>> It's certainly not the latest and greatest, >> >>> >> >>> CPU: Intel(R) Core(TM)2 Duo CPU T7250 @ 2.00GHz >> (1995.04-MHz >> >>> >> >>> K8-class CPU) >> >>> >> >> >> >>> >> >> If you're content to use a compiler from a package you can save >> >>> >> >> a >> >>> >> >> lot >> >>> >> >> of time by building with `CROSS_TOOLCHAIN=llvm13` and >> >>> >> >> `WITHOUT_TOOLCHAIN=yes`. Or, instead of WITHOUT_TOOLCHAIN >> >>> >> >> perhaps >> >>> >> >> `WITHOUT_CLANG=yes`, `WITHOUT_LLD=yes` and `WITHOUT_LLDB=yes`. >> >>> >> > >> >>> >> > (re-send to list, sorry) >> >>> >> > Can we disconnect the compiler optimisation flag for base and >> >>> >> > clang? >> >>> >> > I >> >>> >> > don't need the compiler to be build with -O2 but I want the >> >>> >> > resulting >> >>> >> > base system to have optimisations enabled. >> >>> >> > Right now, looks like both get -O2 and a lot of time is spent on >> >>> >> > optimising the compiler (for no good reason). >> >>> >> > >> >>> >> > >> >>> >> >> >>> > >> >> >> > >> >> >