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

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To: Linus Torvalds <torvalds@...>
Cc: Paul Mackerras <paulus@...>, Benjamin Herrenschmidt <benh@...>, Steven Rostedt <rostedt@...>, LKML <linux-kernel@...>, <linuxppc-dev@...>, Andrew Morton <akpm@...>, Ingo Molnar <mingo@...>, Thomas Gleixner <tglx@...>
Date: Tuesday, November 18, 2008 - 6:24 am

On Tuesday 18 November 2008 13:08, Linus Torvalds wrote:

It's much harder to do this with powerpc I think because they would need
to calculate 8 hashes and touch 8 cachelines to prefill 8 translations,
wouldn't they?



The per-page processing costs are interesting too, but IMO there is more
work that should be done to speed up order-0 pages. The patches I had to
remove the sync instruction for smp_mb() in unlock_page sped up pagecache
throughput (populate, write(2), reclaim) on my G5 by something really
crazy like 50% (most of that's in, but I'm still sitting on that fancy
unlock_page speedup to remove the final smp_mb).

I suspect some of the costs are also in powerpc specific code to insert
linux ptes into their hash table. I think some of the synchronisation for
those could possibly be shared with generic code so you don't need the
extra layer of locks there.
--
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Messages in current thread:
Large stack usage in fs code (especially for PPC64), Steven Rostedt, (Mon Nov 17, 4:34 pm)
Re: Large stack usage in fs code (especially for PPC64), Benjamin Herrenschmidt, (Mon Nov 17, 7:30 pm)
Re: Large stack usage in fs code (especially for PPC64), Benjamin Herrenschmidt, (Mon Nov 17, 7:03 pm)
Re: Large stack usage in fs code (especially for PPC64), Christoph Hellwig, (Tue Nov 18, 5:53 am)
Re: Large stack usage in fs code (especially for PPC64), Linus Torvalds, (Mon Nov 17, 5:09 pm)
Re: Large stack usage in fs code (especially for PPC64), Benjamin Herrenschmidt, (Mon Nov 17, 7:13 pm)
Re: Large stack usage in fs code (especially for PPC64), Linus Torvalds, (Mon Nov 17, 7:28 pm)
Re: Large stack usage in fs code (especially for PPC64), Benjamin Herrenschmidt, (Tue Nov 18, 3:25 am)
Re: Large stack usage in fs code (especially for PPC64), Paul Mackerras, (Mon Nov 17, 8:11 pm)
Re: Large stack usage in fs code (especially for PPC64), Linus Torvalds, (Mon Nov 17, 10:08 pm)
Re: Large stack usage in fs code (especially for PPC64), Nick Piggin, (Tue Nov 18, 6:24 am)
Re: Large stack usage in fs code (especially for PPC64), Linus Torvalds, (Tue Nov 18, 12:02 pm)
Re: Large stack usage in fs code (especially for PPC64), Paul Mackerras, (Tue Nov 18, 7:44 am)
Re: Large stack usage in fs code (especially for PPC64), Paul Mackerras, (Mon Nov 17, 6:53 pm)
Re: Large stack usage in fs code (especially for PPC64), Andrew Morton, (Mon Nov 17, 5:08 pm)
Re: Large stack usage in fs code (especially for PPC64), Linus Torvalds, (Mon Nov 17, 5:23 pm)
Re: Large stack usage in fs code (especially for PPC64), Andrew Morton, (Mon Nov 17, 5:31 pm)
Re: Large stack usage in fs code (especially for PPC64), Benjamin Herrenschmidt, (Mon Nov 17, 7:17 pm)
Re: Large stack usage in fs code (especially for PPC64), Linus Torvalds, (Mon Nov 17, 5:42 pm)
Re: Large stack usage in fs code (especially for PPC64), Steven Rostedt, (Mon Nov 17, 4:59 pm)
Re: Large stack usage in fs code (especially for PPC64), Steven Rostedt, (Mon Nov 17, 10:29 pm)
Re: Large stack usage in fs code (especially for PPC64), Paul Mackerras, (Mon Nov 17, 10:36 pm)
Re: Large stack usage in fs code (especially for PPC64), David Miller, (Tue Nov 18, 1:40 am)
Re: Large stack usage in fs code (especially for PPC64), Benjamin Herrenschmidt, (Mon Nov 17, 7:04 pm)
Re: Large stack usage in fs code (especially for PPC64), Paul Mackerras, (Mon Nov 17, 6:16 pm)
Re: Large stack usage in fs code (especially for PPC64), Steven Rostedt, (Mon Nov 17, 7:30 pm)
Re: Large stack usage in fs code (especially for PPC64), Linus Torvalds, (Mon Nov 17, 5:18 pm)
Re: Large stack usage in fs code (especially for PPC64), Steven Rostedt, (Mon Nov 17, 8:54 pm)
Re: Large stack usage in fs code (especially for PPC64), Paul Mackerras, (Mon Nov 17, 9:05 pm)
Re: Large stack usage in fs code (especially for PPC64), Steven Rostedt, (Mon Nov 17, 9:41 pm)
Re: Large stack usage in fs code (especially for PPC64), Steven Rostedt, (Mon Nov 17, 10:01 pm)
Re: Large stack usage in fs code (especially for PPC64), Pekka Enberg, (Mon Nov 17, 5:25 pm)