On 02/02/2016 10:51 PM, David Rientjes wrote: > On Thu, 28 Jan 2016, David Rientjes wrote: > >> On Thu, 28 Jan 2016, Christian Borntraeger wrote: >> >>> Indeed, I only touched the identity mapping and dump stack. >>> The question is do we really want to change free_init_pages as well? >>> The unmapping during runtime causes significant overhead, but the >>> unmapping after init imposes almost no runtime overhead. Of course, >>> things get fishy now as what is enabled and what not. >>> >>> Kconfig after my patch "mm/debug_pagealloc: Ask users for default setting of debug_pagealloc" >>> (in mm) now states >>> ----snip---- >>> By default this option will have a small overhead, e.g. by not >>> allowing the kernel mapping to be backed by large pages on some >>> architectures. Even bigger overhead comes when the debugging is >>> enabled by DEBUG_PAGEALLOC_ENABLE_DEFAULT or the debug_pagealloc >>> command line parameter. >>> ----snip---- >>> >>> So I am tempted to NOT change free_init_pages, but the x86 maintainers >>> can certainly decide differently. Ingo, Thomas, H. Peter, please advise. >>> >> >> I'm sorry, but I thought the discussion of the previous version of the >> patchset led to deciding that all CONFIG_DEBUG_PAGEALLOC behavior would be >> controlled by being enabled on the commandline and checked with >> debug_pagealloc_enabled(). >> >> I don't think we should have a CONFIG_DEBUG_PAGEALLOC that does some stuff >> and then a commandline parameter or CONFIG_DEBUG_PAGEALLOC_ENABLE_DEFAULT >> to enable more stuff. It should either be all enabled by the commandline >> (or config option) or split into a separate entity. >> CONFIG_DEBUG_PAGEALLOC_LIGHT and CONFIG_DEBUG_PAGEALLOC would be fine, but >> the current state is very confusing about what is being done and what >> isn't. >> > > Ping? > https://lkml.org/lkml/2016/1/29/266 ? -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
