From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Zoltan Menyhart <Zoltan.Menyhart@free.fr>
Cc: Hugh Dickins <hugh@veritas.com>,
Zoltan Menyhart <Zoltan.Menyhart@bull.net>,
linux-mm@kvack.org
Subject: Re: Any reason for passing "tlb" to "free_pgtables()" by address?
Date: Tue, 09 May 2006 11:40:02 +1000 [thread overview]
Message-ID: <445FF2F2.6080102@yahoo.com.au> (raw)
In-Reply-To: <445FBD1B.6080404@free.fr>
Zoltan Menyhart wrote:
> Hugh Dickins wrote:
>
>> Personally I'd prefer not to make your change right now - it seems
>> a shame to make that cosmetic change without addressing the real
>> latency issue; but I've no strong feeling against your patch.
>
>
> Could you please explain what your plans are?
Long term, we would like to make the mmu_gather paths preemptible and
reentrant so the latency hacks can go away, and we don't end up with
awful things like a tlb flush after unmapping every 8 pages for
CONFIG_PREEMPT.
I posted a quick RFC a while back to implement my "gather in place"
idea: http://www.ussg.iu.edu/hypermail/linux/kernel/0603.2/0499.html
Hugh has a different approach, but neither is particularly urgent at
this stage.
In the short term, we might still like to be able to do latency breaks
in free_pgtables so it would make sense to keep the code the way it is.
>
> How much do you think it is worth to optimize "free_pgtables()",
> knowing that:
> - PTE, PMD and PUD pages are freed seldom (wrt. the leaf pages)
> - The number of these pages is much more less than
> that of the leaf pages.
Virtual address space can still be vast and sparse. Even with 32 bits,
we could probably trigger high latencies here.
Nick
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next prev parent reply other threads:[~2006-05-09 1:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-05 10:53 Any reason for passing "tlb" to "free_pgtables()" by address? Zoltan Menyhart
2006-05-05 12:41 ` Hugh Dickins
2006-05-08 21:50 ` Zoltan Menyhart
2006-05-09 1:40 ` Nick Piggin [this message]
2006-05-09 11:23 ` Hugh Dickins
2006-05-09 19:30 ` Zoltan Menyhart
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