Re: Build time data

[Darren Hart <dvhart@linux.intel.com>]

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On 04/12/2012 01:00 AM, Martin Jansa wrote:
> On Thu, Apr 12, 2012 at 01:05:00PM +0530, Joshua Immanuel wrote:
>> Darren,
>> 
>> On Wed, 2012-04-11 at 17:30 -0700, Darren Hart wrote:
>>> I run on a beast with 12 cores, 48GB of RAM, OS and sources on
>>> a G2 Intel SSD, with two Seagate Barracudas in a RAID0 array
>>> for my /build partition. I run a headless Ubuntu 11.10 (x86_64)
>>> installation running the 3.0.0-16-server kernel. I can build
>>> core-image-minimal in < 30 minutes and core-image-sato in < 50
>>> minutes from scratch.
> 
> why not use so much RAM for WORKDIR in tmpfs? I bought 16GB just to
> be able to do my builds in tmpfs and keep only more permanent data
> on RAID.

We've done some experiments with tmpfs, adding Beth on CC. If I recall
correctly, my RAID0 array with the mount options I specified
accomplishes much of what tmpfs does for me without the added setup.
With a higher commit interval, the kernel doesn't try to sync the
dcache with the disks as frequently (eg not even once during a build),
so it's effectively writing to memory (although there is still plenty
of IO occurring).

The other reason is that while 48GB is plenty for a single build, I
often run many builds in parallel, sometimes in virtual machines when
I need to reproduce or test something on different hosts.

For example:
https://picasaweb.google.com/lh/photo/7PCrqXQqxL98SAY1ecNzDdMTjNZETYmyPJy0liipFm0?feat=directlink


- -- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel
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