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From: Segher Boessenkool <segher@kernel.crashing.org>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: linuxppc-dev@lists.ozlabs.org,
	Suraj Jitindar Singh <sjitindarsingh@gmail.com>,
	David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH kernel] prom_init: Fetch flatten device tree from the system firmware
Date: Fri, 3 May 2019 10:32:17 -0500	[thread overview]
Message-ID: <20190503153217.GN8599@gate.crashing.org> (raw)
In-Reply-To: <20190501034221.18437-1-aik@ozlabs.ru>

On Wed, May 01, 2019 at 01:42:21PM +1000, Alexey Kardashevskiy wrote:
> At the moment, on 256CPU + 256 PCI devices guest, it takes the guest
> about 8.5sec to fetch the entire device tree via the client interface
> as the DT is traversed twice - for strings blob and for struct blob.
> Also, "getprop" is quite slow too as SLOF stores properties in a linked
> list.

Most OF implementations do it that way.  An optimisation that can help
a lot is to cache the last accessed node / prop.  This of course then
requires you to invalidate that cache at many places you did not think
about :-/

> However, since [1] SLOF builds flattened device tree (FDT) for another
> purpose. [2] adds a new "fdt-fetch" client interface for the OS to fetch
> the FDT.

Since Linux does not do much more with the device tree, this should
work great for it.


Segher

  parent reply	other threads:[~2019-05-03 15:34 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-01  3:42 [PATCH kernel] prom_init: Fetch flatten device tree from the system firmware Alexey Kardashevskiy
2019-05-02  4:27 ` David Gibson
2019-05-03  0:10   ` Stewart Smith
2019-05-03  2:35     ` David Gibson
2019-05-06  2:21       ` Alexey Kardashevskiy
2019-05-03 15:35     ` Segher Boessenkool
2019-05-03 15:32 ` Segher Boessenkool [this message]
2019-05-30  7:09 ` Alexey Kardashevskiy
2019-05-30 19:37   ` Segher Boessenkool
2019-05-31  1:03     ` Benjamin Herrenschmidt
2019-06-02 23:23       ` Segher Boessenkool
2019-06-03  2:56         ` Alexey Kardashevskiy
2019-06-03 21:18           ` Benjamin Herrenschmidt
2019-06-03 23:49             ` Segher Boessenkool
2019-06-04  0:32               ` David Gibson
2019-06-03 23:42           ` Segher Boessenkool
2019-06-04  0:18             ` Benjamin Herrenschmidt
2019-06-04  5:00             ` Alexey Kardashevskiy

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