On Wed, 2013-09-25 at 02:27 +0800, Zhang Yanfei wrote: > From: Tang Chen <tangc...@cn.fujitsu.com> > > The Linux kernel cannot migrate pages used by the kernel. As a result, kernel > pages cannot be hot-removed. So we cannot allocate hotpluggable memory for > the kernel. > > ACPI SRAT (System Resource Affinity Table) contains the memory hotplug info. > But before SRAT is parsed, memblock has already started to allocate memory > for the kernel. So we need to prevent memblock from doing this. > > In a memory hotplug system, any numa node the kernel resides in should > be unhotpluggable. And for a modern server, each node could have at least > 16GB memory. So memory around the kernel image is highly likely > unhotpluggable. > > So the basic idea is: Allocate memory from the end of the kernel image and > to the higher memory. Since memory allocation before SRAT is parsed won't > be too much, it could highly likely be in the same node with kernel image. > > The current memblock can only allocate memory top-down. So this patch > introduces > a new bottom-up allocation mode to allocate memory bottom-up. And later > when we use this allocation direction to allocate memory, we will limit > the start address above the kernel. > > Signed-off-by: Tang Chen <tangc...@cn.fujitsu.com> > Signed-off-by: Zhang Yanfei <zhangyan...@cn.fujitsu.com>
: > /** > + * __memblock_find_range - find free area utility > + * @start: start of candidate range > + * @end: end of candidate range, can be %MEMBLOCK_ALLOC_{ANYWHERE|ACCESSIBLE} > + * @size: size of free area to find > + * @align: alignment of free area to find > + * @nid: nid of the free area to find, %MAX_NUMNODES for any node > + * > + * Utility called from memblock_find_in_range_node(), find free area > bottom-up. > + * > + * RETURNS: > + * Found address on success, 0 on failure. > + */ > +static phys_addr_t __init_memblock > +__memblock_find_range(phys_addr_t start, phys_addr_t end, phys_addr_t size, Similarly, how about name this function as __memblock_find_range_bottom_up()? > + phys_addr_t align, int nid) > +{ > + phys_addr_t this_start, this_end, cand; > + u64 i; > + > + for_each_free_mem_range(i, nid, &this_start, &this_end, NULL) { > + this_start = clamp(this_start, start, end); > + this_end = clamp(this_end, start, end); > + > + cand = round_up(this_start, align); > + if (cand < this_end && this_end - cand >= size) > + return cand; > + } > + > + return 0; > +} > + > +/** > * __memblock_find_range_rev - find free area utility, in reverse order > * @start: start of candidate range > * @end: end of candidate range, can be %MEMBLOCK_ALLOC_{ANYWHERE|ACCESSIBLE} > @@ -93,7 +128,7 @@ static long __init_memblock > memblock_overlaps_region(struct memblock_type *type, > * Utility called from memblock_find_in_range_node(), find free area > top-down. > * > * RETURNS: > - * Found address on success, %0 on failure. > + * Found address on success, 0 on failure. > */ > static phys_addr_t __init_memblock > __memblock_find_range_rev(phys_addr_t start, phys_addr_t end, > @@ -127,13 +162,24 @@ __memblock_find_range_rev(phys_addr_t start, > phys_addr_t end, > * > * Find @size free area aligned to @align in the specified range and node. > * > + * When allocation direction is bottom-up, the @start should be greater > + * than the end of the kernel image. Otherwise, it will be trimmed. The > + * reason is that we want the bottom-up allocation just near the kernel > + * image so it is highly likely that the allocated memory and the kernel > + * will reside in the same node. > + * > + * If bottom-up allocation failed, will try to allocate memory top-down. > + * > * RETURNS: > - * Found address on success, %0 on failure. > + * Found address on success, 0 on failure. > */ > phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t start, > phys_addr_t end, phys_addr_t size, > phys_addr_t align, int nid) > { > + int ret; > + phys_addr_t kernel_end; > + > /* pump up @end */ > if (end == MEMBLOCK_ALLOC_ACCESSIBLE) > end = memblock.current_limit; > @@ -141,6 +187,37 @@ phys_addr_t __init_memblock > memblock_find_in_range_node(phys_addr_t start, > /* avoid allocating the first page */ > start = max_t(phys_addr_t, start, PAGE_SIZE); > end = max(start, end); > + kernel_end = __pa_symbol(_end); Please address the issue in __pa_symbol() that Andrew pointed out. Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/