On Tue, 18 Feb 2014, Andrew Morton wrote: > > I'm not sure I understand why we want to be independent of PAGE_SIZE since > > we're still relying on PAGE_CACHE_SIZE. Don't you mean to do > > > > #define MAX_READAHEAD ((512*PAGE_SIZE)/PAGE_CACHE_SIZE) > > MAX_READAHEAD is in units of "pages". > > This: > > +#define MAX_READAHEAD ((512*4096)/PAGE_CACHE_SIZE) > > means "two megabytes", and is implemented in a way to ensure that > MAX_READAHEAD=2mb on 4k pagesize as well as on 64k pagesize. Because > we don't want variations in PAGE_SIZE to cause alterations in readahead > behavior. > Ah, ok, so 2MB is the magic value that we limit readhead to on all architectures. 512 * 4096 is a strange way to write 2MB, but ok :) -- 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>