On 06/01/17 22:43, Andrew Morton wrote: > On Fri, 25 Nov 2016 18:55:18 +0000 Paul Burton <paul.burton@xxxxxxxxxx> wrote: > >> When using a sparse memory model memmap_init_zone() when invoked with >> the MEMMAP_EARLY context will skip over pages which aren't valid - ie. >> which aren't in a populated region of the sparse memory map. However if >> the memory map is extremely sparse then it can spend a long time >> linearly checking each PFN in a large non-populated region of the memory >> map & skipping it in turn. >> >> When CONFIG_HAVE_MEMBLOCK_NODE_MAP is enabled, we have sufficient >> information to quickly discover the next valid PFN given an invalid one >> by searching through the list of memory regions & skipping forwards to >> the first PFN covered by the memory region to the right of the >> non-populated region. Implement this in order to speed up >> memmap_init_zone() for systems with extremely sparse memory maps. > Could we have a changelog which includes some timing measurements? > That permits others to understand the value of this patch. > I have tested this patch on a virtual model of a Samurai CPU with a sparse memory map. The kernel boot time drops from 109 to 62 seconds. James -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>