On Mon, Dec 27, 2021 at 09:44:24AM +0800, Kefeng Wang wrote: > > On 2021/12/27 1:36, Christophe Leroy wrote: > > > > Le 26/12/2021 à 09:39, Kefeng Wang a écrit : > > > Add HUGE_VMALLOC_DEFAULT_ENABLED to let user to choose whether or > > > not enable huge vmalloc mappings by default, and this could make > > > more architectures to enable huge vmalloc mappings feature but > > > don't want to enable it by default. > > > > > > Add hugevmalloc=on/off parameter to enable or disable this feature > > > at boot time, nohugevmalloc is still supported and equivalent to > > > hugevmalloc=off. > > > > Is there a real added value to have the user be able to select that ? > > > > If the architecture supports it, is there any good reason to not use it ? > > There are some disadvantages[1], one of the main concerns is the possible > > memory waste, we have backported this feature to our kernel 5.10, but our > > downstream in our some scenario(especially in embedded), they don't want > > it enabled by default, and others want it, this is why patch1 comes. > > > > > Why not just do like PPC and enable it by default ? Why should it be > > enabled by default on PPC but disabled by default on ARM64 and X86 ? > > The PPC is default enabled, we don't changes this behavior. > > Maybe upstream is not care about this, as I said in cover-letter, if > arm64/x86 > > don't want patch1, we could only just select config to enable it. > > Let's wait for more feedback. We should not have different defaults by architecture. Either we change the default for PPC, or x86 & arm should have the same default as PPC.
