From mboxrd@z Thu Jan  1 00:00:00 1970
From: erik quanstrom <quanstro@quanstro.net>
Date: Sun,  9 Jan 2011 17:00:46 -0500
To: 9fans@9fans.net
Message-ID: <7488d953e16839c316b7590d66edcb6c@ladd.quanstro.net>
In-Reply-To: <20110109213849.939D75B42@mail.bitblocks.com>
References: <16094d5a594bfa72dd0e9ac6f3f8b31c@plug.quanstro.net>
	<AANLkTin9Ft5OS2mgJ3y4Sh+DbpFvgPvCVh-hxJoT2Ed0@mail.gmail.com>
	<20110109195426.D1ED35B42@mail.bitblocks.com>
	<da8020577332c3641d8ba418cd1b9376@ladd.quanstro.net>
	<20110109213849.939D75B42@mail.bitblocks.com>
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
Subject: Re: [9fans] fs performance
Topicbox-Message-UUID: 931f3fca-ead6-11e9-9d60-3106f5b1d025

> > i also think that your examples don't translate well into the
> > plan 9 world.  we trade performance for keeping ramfs out of
> > the kernel, etc. (620mb/s on my much slower machine, btw.)
>
> This is for dd </dev/zero >/dev/null?  What do you get for
> various block sizes?

that's for dd -if /dev/zero -of /n/testramfs/bigfile -bs 128k -count `{aux/number 100m/128k}

the block size won't matter much, since ramfs will get 8k writes
no matter what.

> If you are getting 620MBps that means you will definitely not
> exceed that number for disk based filesystems.

wrong-o!

when i first started testing the myricom 10gbe in 2006, i was able
to get 470MB/s from an sr with the aoe driver with no caching
or readahead on the plan 9 side.  by today's standards, those were
very slow systems.

i don't have the time to set up this test rig right now, but i think
it's safe to assume that we can pound this performance with modern
hardware and a modern aoe appliance.

but even with 470ms/s from the disk, with memory caching and
ken fs's good performance (no context switches, no tlb flushes),
it's safe to assume that we can already beat 620mb/s from the
file server.

what you're seeing is the fact that ramfs is just plain slow.

- erik