From: Ariadne Conill <ariadne@dereferenced.org>
To: ~alpine/users@lists.alpinelinux.org
Subject: Re: [LVM] Strange disk perf on fresh install
Message-ID: <1620199.9KrzfI0oD8@nanabozho>
In-Reply-To: <03b0aa41-a5c2-7a96-b8d2-2b8f4c80c1e0@cri.epita.fr>
References: <03b0aa41-a5c2-7a96-b8d2-2b8f4c80c1e0@cri.epita.fr>
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Date: Thu, 03 Dec 2020 03:29:29 GMT


Hello,

On Wednesday, December 2, 2020 11:21:30 AM MST Sevan wrote:
> Hello everyone,
> 
> I recently installed Alpine on a dedicated server using LVM for root and
> swap partitions. But after some benchmarks, I noticed that the hard disk
> speed of my new Alpine install was noticeably slower then on other
> distro (Archinux and Debian in this case).
> 
> I then ran more benchmarks using `fio`. Here is my methodology and the
> benchs results:
> 
> # Benchmark commands:
>      Read:
>          fio --name=alpine-read --ioengine=posixaio --rw=read --bs=4k
>          --numjobs=1 --size=4g --iodepth=1 --runtime=60 --time_based
>          --end_fsync=1
>      Write:
>          fio --name=alpine-write --ioengine=posixaio --rw=write --bs=4k
>          --numjobs=1 --size=4g --iodepth=1 --runtime=60 --time_based
>          --end_fsync=1
> 
> # Benchmark setups:
> 
> ## Server:
>      Hardware specs:
>          - GPT on a BIOS only capable motherboard with a `lvmsys`
>            Alpine install
>          - Hardware raid1 - HP SmartArray p222
> 
>      Alpine - LVM:
>          READ: bw=154MiB/s (162MB/s)
>          WRITE: bw=86.3MiB/s (90.5MB/s)
> 
>      Archlinux - LVM (Alpine LVM partitions mounted on archlinux liveCD):
>          READ: bw=236MiB/s (247MB/s)
>          WRITE: bw=126MiB/s (132MB/s)
> 
> ## VM (VirtualBox):
>      Hardware specs:
>          - Basic `lvmsys` Alpine install on a laptop with a NVMe SSD
> 
>      Alpine - LVM:
>          READ: bw=96.2MiB/s (101MB/s)
>          WRITE: bw=93.5MiB/s (98.0MB/s)
> 
>      Archlinux - LVM (Alpine LVM partitions mounted on archlinux liveCD):
>          READ: bw=354MiB/s (371MB/s)
>          WRITE: bw=237MiB/s (248MB/s)
> 
> As you can see, Alpine performances are quite bad, is this an expected
> behavior ?
> 
> If it's not, where should I try to look for a fix ? Kernel config ? LVM
> using musl ?

Two things you may want to try.

Make sure write cache is enabled: sdparm -s WCE=y /dev/sda (or whatever your 
RAID volume is).

Secondly, Alpine uses mq-deadline scheduler by default on rotational media, 
this trades linear read/write performance for better seek latencies.  You 
might try using kyber scheduler instead: echo kyber > /sys/block/sda/queue/
scheduler

Ariadne