Messages in this thread Patch in this message | | | From | Mel Gorman <> | Subject | [PATCH 3/5] x86 - Specify amount of kernel memory at boot time | Date | Thu, 19 Jan 2006 19:09:01 +0000 (GMT) |
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This patch was originally written by Kamezawa Hiroyuki.
It should be possible for the administrator to specify at boot-time how much memory should be used for the kernel and how much should go to ZONE_EASYRCLM. After this patch is applied, the boot option kernelcore= can be used to specify how much memory should be used by the kernel.
(Note that Kamezawa called this parameter coremem= . This was renamed because of the way ppc64 parses command line arguments and would confuse coremem= with mem=. The name was chosen that could be used across architectures)
The value of kernelcore is important. If it is too small, there will be more pressure on ZONE_NORMAL and a potential loss of performance. If it is about 896MB, it means that ZONE_HIGHMEM will have a size of zero. Any differences in tests will depend on whether CONFIG_HIGHPTE is set in the standard kernel or not. With lots of memory, the ideal is to specify a kernelcore that gives ZONE_NORMAL it's full size and a ZONE_HIGHMEM for PTEs. The right value depends, like any tunable, on the workload.
It is also important to note that if kernelcore is less than the maximum size of ZONE_NORMAL, GFP_HIGHMEM allocations will use ZONE_NORMAL, not the reachable portion of ZONE_EASYRCLM.
Signed-off-by: Mel Gorman <mel@csn.ul.ie> diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.16-rc1-mm1-102_addzone/arch/i386/kernel/setup.c linux-2.6.16-rc1-mm1-103_x86coremem/arch/i386/kernel/setup.c --- linux-2.6.16-rc1-mm1-102_addzone/arch/i386/kernel/setup.c 2006-01-19 11:21:57.000000000 +0000 +++ linux-2.6.16-rc1-mm1-103_x86coremem/arch/i386/kernel/setup.c 2006-01-19 11:44:49.000000000 +0000 @@ -121,6 +121,9 @@ int bootloader_type; /* user-defined highmem size */ static unsigned int highmem_pages = -1; +/* user-defined easy-reclaim-size */ +static unsigned int core_mem_pages = -1; +static unsigned int easyrclm_pages = 0; /* * Setup options */ @@ -921,6 +924,15 @@ static void __init parse_cmdline_early ( */ else if (!memcmp(from, "vmalloc=", 8)) __VMALLOC_RESERVE = memparse(from+8, &from); + /* + * kernelcore=size sets the amount of memory for use for + * kernel allocations that cannot be reclaimed easily. + * The remaining memory is set aside for easy reclaim + * for features like memory remove or huge page allocations + */ + else if (!memcmp(from, "kernelcore=",11)) { + core_mem_pages = memparse(from + 11, &from) >> PAGE_SHIFT; + } next_char: c = *(from++); @@ -990,6 +1002,17 @@ void __init find_max_pfn(void) } } +unsigned long __init calculate_core_memory(unsigned long max_low_pfn) +{ + if (max_low_pfn < core_mem_pages) { + highmem_pages -= (core_mem_pages - max_low_pfn); + } else { + max_low_pfn = core_mem_pages; + highmem_pages = 0; + } + easyrclm_pages = max_pfn - core_mem_pages; + return max_low_pfn; +} /* * Determine low and high memory ranges: */ @@ -1046,6 +1069,8 @@ unsigned long __init find_max_low_pfn(vo printk(KERN_ERR "ignoring highmem size on non-highmem kernel!\n"); #endif } + if (core_mem_pages != -1) + max_low_pfn = calculate_core_memory(max_low_pfn); return max_low_pfn; } @@ -1166,7 +1191,8 @@ void __init zone_sizes_init(void) zones_size[ZONE_DMA] = max_dma; zones_size[ZONE_NORMAL] = low - max_dma; #ifdef CONFIG_HIGHMEM - zones_size[ZONE_HIGHMEM] = highend_pfn - low; + zones_size[ZONE_HIGHMEM] = highend_pfn - low - easyrclm_pages; + zones_size[ZONE_EASYRCLM] = easyrclm_pages; #endif } free_area_init(zones_size); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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