Johannes Weiner <han...@cmpxchg.org> writes: > On Thu, Mar 30, 2017 at 08:45:56AM +0800, Huang, Ying wrote: >> Johannes Weiner <han...@cmpxchg.org> writes: >> >> > On Tue, Mar 28, 2017 at 01:32:01PM +0800, Huang, Ying wrote: >> >> @@ -499,6 +499,19 @@ config FRONTSWAP >> >> >> >> If unsure, say Y to enable frontswap. >> >> >> >> +config ARCH_USES_THP_SWAP_CLUSTER >> >> + bool >> >> + default n >> > >> > This is fine. >> > >> >> +config THP_SWAP_CLUSTER >> >> + bool >> >> + depends on SWAP && TRANSPARENT_HUGEPAGE && ARCH_USES_THP_SWAP_CLUSTER >> >> + default y >> >> + help >> >> + Use one swap cluster to hold the contents of the THP >> >> + (Transparent Huge Page) swapped out. The size of the swap >> >> + cluster will be same as that of THP. >> > >> > But this is a super weird thing to ask the user. How would they know >> > what to say, if we don't know? I don't think this should be a config >> > knob at all. Merge the two config items into a simple >> >> The user will not see this, because there is no string after "bool" to >> let user to select it. The help here is for document only, so that >> architecture developers could know what this is for. > > Oh, I missed that. My bad! > >> > config THP_SWAP_CLUSTER >> > bool >> > default n >> > >> > and let the archs with reasonable THP sizes select it. >> >> This will have same effect as the original solution except the document >> is removed. > > Then I still don't understand why we need two config symbols. Can't > archs select the documented THP_SWAP_CLUSTER directly? > > The #ifdef in swapfile.c could check THP && THP_SWAP_CLUSTER. > > Am I missing something?
I use two config symbols just to save some typing, instead of #ifdef CONFIG_THP_SWAP_CLUSTER it will be, #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_THP_SWAP_CLUSTER) or #if defined(CONFIG_SWAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE) && defined(CONFIG_THP_SWAP_CLUSTER) Best Regards, Huang, Ying
