linux-mips
[Top] [All Lists]

Re: Question about Context register in TLB refilling

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: Question about Context register in TLB refilling
From: "Gleb O. Raiko" <raiko@niisi.msk.ru>
Date: Mon, 18 Oct 2010 14:46:02 +0400
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>, Kevin Cernekee <cernekee@gmail.com>, "wilbur.chan" <wilbur512@gmail.com>, Linux MIPS Mailing List <linux-mips@linux-mips.org>
In-reply-to: <20101018000030.GB31080@linux-mips.org>
Organization: NIISI RAN
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <AANLkTikP=77Tq=QzFVwexr8fMHg5qmX8fbRjfdkoNSGr@mail.gmail.com> <AANLkTikbw1F+jBhsFFyX0vT6CCAqckzLHK3MK2WtTZiA@mail.gmail.com> <alpine.LFD.2.00.1010172025110.15889@eddie.linux-mips.org> <20101018000030.GB31080@linux-mips.org>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.5) Gecko/20091204 Thunderbird/3.0
On 18.10.2010 4:00, Ralf Baechle wrote:
The aliasing problem is solvable and it may be worth to revisit that old
piece of code again now 15 years later.

Before anybody will start to prepare patches, I'd like to note using c0_context allows less than 128 processes (their mm contexts in fact but who cares) to be directly mapped on 32-bit cpus. So, some kind of caching needs to be implemented and it will add overhead on every mm switch. Sure, this overhead might be bounded for a real case where there is a small number of processes, so they all fit in the cache.
--- Beware, wild assumptions here ---
I'm afraid the cost of such caching still will be higher than loading pgd_current even from main memory on tlb refill.
--- End of wild assumptions ---

Gleb.

<Prev in Thread] Current Thread [Next in Thread>