|| ||Christoph Lameter <firstname.lastname@example.org>|
|| ||[RFC 0/8] Reduce MAX_NR_ZONES and remove useless zones.|
|| ||Mon, 3 Jul 2006 14:55:34 -0700 (PDT)|
|| ||email@example.com, Hugh Dickins <firstname.lastname@example.org>,
Con Kolivas <email@example.com>,
Marcelo Tosatti <firstname.lastname@example.org>,
Nick Piggin <email@example.com>,
Christoph Lameter <firstname.lastname@example.org>, Andi Kleen <email@example.com>|
I keep seeing zones on various platforms that are never used and wonder
why we compile support for them into the kernel.
IA64 on SGI for example only uses ZONE_DMA other IA64 platforms can
also use ZONE_NORMAL. So we have 50% useless zones. Large amounts
of memory go to waste with systems with a few hundred nodes and a few
My x86_64 system seems to only use ZONE_DMA and ZONE_DMA32. I never see pages
in ZONE_NORMAL (probably because I have less than 4G memory).
And ZONE_HIGHMEM on a 64 bit system? We can address all memory. I keep
seeing all the highmem counters as zero on ia64 and x86_64 and even on
Then it seems that ZONE_DMA32 is only used on x86_64 but we compile it into
the kernel for all platforms.
This patch makes ZONE_DMA32 and ZONE_HIGHMEM support optional. MAX_NR_ZONES
will be 2 for most non i386 platforms and even for i386 without CONFIG_HIGHMEM
I tested this on IA64 and x86_64. Compiles fine on i386 with and without
The patchset consists of 8 patches that are following this message.
One could go even further than this patchset and also make ZONE_DMA optional
because some platforms do not need a separate DMA zone and can do DMA to all
of memory. This could reduce MAX_NR_ZONES to 1.