From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hiroyuki KAMEZAWA Date: Thu, 07 Oct 2004 06:28:29 +0000 Subject: Re: [RFC/PATCH] pfn_valid() more generic : arch independent part[0/2] Message-Id: <4164E20D.5020400@jp.fujitsu.com> List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Luck, Tony" Cc: "Martin J. Bligh" , LinuxIA64 , linux-mm Hi, Luck, Tony wrote: >>Because pfn_valid() often returns 0 in inner loop of free_pages_bulk(), >>I want to avoid page fault caused by using get_user() in pfn_valid(). > > > How often? Surely this is only a problem at the edges of blocks > of memory? I suppose it depends on whether your discontig memory > appears in blocks much smaller than MAXORDER. But even there it > should only be an issue coalescing buddies that are bigger than > the granule size (since all of the pages in a granule on ia64 are > guaranteed to exist, the buddy of any page must also exist). > Currently, my Tiger4 shows memory map like this. this is a record of memmap_init() called by virtual_memmap_init(). NOTE: MAX_ORDER is 4Gbytes. mem_map(1) from 36e length 1fb6d --- ZONE_DMA (36e to 1fedb) mem_map(2) from 1fedc length 124 --- ZONE_DMA (1fedc to 20000) ZONE_DMA is 0G to 4G. mem_map(3) from 40000 length 40000 --- ZONE_NORMAL (4G to 8G, this mem_map is aligned) mem_map(4) from a0000 length 20000 --- ZONE_NORMAL (10G to 12G) mem_map(5) from bfedc length 124 --- ZONE_NORMAL (this is involved in mem_map(4)) ZONE_NORMAL is 4G to 12G. node's start_pfn and end_pfn is aligned to granule size, but holes in memmap is not. The vmemmap is aligned to # of page structs in one page. virtual_memmap_init() is called directly from efi_memmap_walk() and it doesn't take granule size of ia64 into account. Hmm.... It looks what I should do is to make memmap to be aligned to ia64's granule. thanks for your advise. I maybe considerd this problem too serious. If vmemmap is aligned, ia64_pfn_valid() will work fine. or only 1 level table will be needed. Thanks. Kame