linux-kernel - Re: Large stack usage in fs code (especially for PPC64)

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Message-Id: <200811182107.12747.nickpiggin@yahoo.com.au>
Date:	Tue, 18 Nov 2008 21:07:12 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linuxppc-dev@...abs.org, Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Large stack usage in fs code (especially for PPC64)

On Tuesday 18 November 2008 09:53, Paul Mackerras wrote:

> I'd love to be able to use a 4k base page size if I could still get
> the reduction in page faults and the expanded TLB reach that we get
> now with 64k pages.  If we could allocate the page cache for large
> files with order-4 allocations wherever possible that would be a good
> start.

That can still have nasty side-effects like fragmentation and 64k
granular reclaim. It also adds complexity to mapping the pages to
userspace.

Christoph's patchset IIRC also only did page cache, wheras I suppose
your kernbench workload is gaining mainly from anonymous page faults.
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