On Mon, Nov 15, 2021 at 01:57:32PM +0000, Matthew Wilcox wrote: > On Mon, Nov 15, 2021 at 09:49:51PM +0800, Peter Xu wrote: > > Clean the code up by merging the device private/exclusive swap entry handling > > with the rest, then we merge the pte clear operation too. > > > > struct* page is defined in multiple places in the function, move it upward. > > Is that actually a good thing? There was a time when declaring > variables more locally helped compilers with liveness analysis and > register allocation. Compilers are probably smarter now. > I see, I don't know the history of that, but I did give it a shot with a patch that recovered all the "struct page*" back to the origin, I found that it'll generated exactly the same assembly of unmap_page_range (actually, the whole mm/memory.o) no matter what. I only tested on an aarch64 system, with below gcc version: $ gcc -v Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/libexec/gcc/aarch64-redhat-linux/11/lto-wrapper Target: aarch64-redhat-linux Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,fortran,objc,obj-c++,ada,go,lto --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --enable-plugin --enable-initfini-array --with-isl=/builddir/build/BUILD/gcc-11.0.1-20210324/obj-aarch64-redhat-linux/isl-install --enable-gnu-indirect-function --build=aarch64-redhat-linux Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 11.0.1 20210324 (Red Hat 11.0.1-0) (GCC) Thanks, -- Peter Xu
