Re: [QUICKLIST 0/4] Arch independent quicklists V2

From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: clameter@sgi.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [QUICKLIST 0/4] Arch independent quicklists V2
Date: Tue, 13 Mar 2007 23:18:07 +1100	[thread overview]
Message-ID: <45F6967F.4020002@yahoo.com.au> (raw)
In-Reply-To: <20070313051109.3215104b.akpm@linux-foundation.org>

Andrew Morton wrote:
>>On Tue, 13 Mar 2007 23:01:11 +1100 Nick Piggin <nickpiggin@yahoo.com.au> wrote:
>>Andrew Morton wrote:

>>>It would be interesting to look at a) leave the page full of random garbage
>>>if we're releasing the whole mm and b) return it straight to the page allocator.
>>
>>Well we have the 'fullmm' case, which avoids all the locked pte operations
>>(for those architectures where hardware pt walking requires atomicity).
> 
> 
> I suspect there are some tlb operations which could be skipped in that case
> too.

Depends on the tlb flush implementation. The generic one doesn't look like
it is all that smart about optimising the fullmm case. It does skip some
tlb flushing though.

>>However we still have to visit those to-be-unmapped parts of the page table
>>to find the pages and free them. So we still at least need to bring it into
>>cache for the read... at which point, the store probably isn't a big burden.
> 
> 
> It means all that data has to be written back.  Yes, I expect it'll prove
> to be less costly than the initial load.

Still, it is something we could try.

-- 
SUSE Labs, Novell Inc.
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