linux-kernel - Re: [PATCH 2.6.20-rc5 1/1] MM: enhance Linux swap subsystem

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Date:	Mon, 29 Jan 2007 13:29:58 +0800
From:	"yunfeng zhang" <zyf.zeroos@...il.com>
To:	"Hugh Dickins" <hugh@...itas.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.20-rc5 1/1] MM: enhance Linux swap subsystem

> You have an interesting idea of "simplifies", given
>  16 files changed, 997 insertions(+), 25 deletions(-)
> (omitting your Documentation), and over 7k more code.
> You'll have to be much more persuasive (with good performance
> results) to get us to welcome your added layer of complexity.

If the whole idea is deployed on Linux, following core objects should be erased
1) anon_vma.
2) pgdata::active/inactive list and relatted methods -- mark_page_accessed etc.
3) PrivatePage::count and mapcount. If core need to share the page, add PG_kmap
   flag. In fact, page::lru_list can safetly be erased too.
4) All cases should be from up to down, especially simplifies debug.

> Please make an effort to support at least i386 3level pagetables:
> you don't actually need >4GB of memory to test CONFIG_HIGHMEM64G.
> HIGHMEM testing shows you're missing a couple of pte_unmap()s,
> in pps_swapoff_scan_ptes() and in shrink_pvma_scan_ptes().

Yes, it's my fault.

> It would be nice if you could support at least x86_64 too
> (you have pte_low code peculiar to i386 in vmscan.c, which is
> preventing that), but that's harder if you don't have the hardware.

Um! Data cmpxchged should include access bit. And I have only x86 PC, memory <
1G. 3level pagetable code copied from Linux other functions.
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