On Fri, 14 Aug 2020 17:10:06 +0200 Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> wrote: > This is a complete rewrite of the page allocator. > > This will bring a few improvements: > * no need to specify the size when freeing > * allocate small areas with a large alignment without wasting memory > * ability to initialize and use multiple memory areas (e.g. DMA) > * more sanity checks > > A few things have changed: > * initialization cannot be done with free_pages like before, > page_alloc_init_area has to be used instead > > Arch-specific changes: > * arm and x86 have been adapted to put all the memory in just one big > area (or two, for x86_64 with highmem). > * s390x instead creates one area below 2GiB and one above; the area > below 2GiB is used for SMP lowcore initialization. I was just wondering why we did not run into that problem before for the css control blocks, but these are statically allocated. > > Details: > Each memory area has metadata at the very beginning. The metadata is a > byte array with one entry per usable page (so, excluding the metadata > itself). Each entry indicates if the page is special (unused for now), > if it is allocated, and the order of the block. Both free and allocated > pages are part of larger blocks. > > Some more fixed size metadata is present in a fixed-size static array. > This metadata contains start and end page frame numbers, the pointer to > the metadata array, and the array of freelists. The array of freelists > has an entry for each possible order (indicated by the macro NLISTS, > defined as BITS_PER_LONG - PAGE_SHIFT). > > On allocation, if the free list for the needed size is empty, larger > blocks are split. When a small allocation with a large alignment is > requested, an appropriately large block is split, to guarantee the > alignment. > > When a block is freed, an attempt will be made to merge it into the > neighbour, iterating the process as long as possible. > > Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> > --- > lib/alloc_page.h | 64 ++++++- > lib/alloc_page.c | 451 ++++++++++++++++++++++++++++++++++++----------- > lib/arm/setup.c | 2 +- > lib/s390x/sclp.c | 11 +- > lib/s390x/smp.c | 2 +- > lib/vmalloc.c | 13 +- > 6 files changed, 427 insertions(+), 116 deletions(-) (...) > diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c > index 2860e9c..d954094 100644 > --- a/lib/s390x/smp.c > +++ b/lib/s390x/smp.c > @@ -190,7 +190,7 @@ int smp_cpu_setup(uint16_t addr, struct psw psw) > > sigp_retry(cpu->addr, SIGP_INITIAL_CPU_RESET, 0, NULL); > > - lc = alloc_pages(1); > + lc = alloc_pages_area(_AREA(1), 1); Add a comment describing what this _AREA(1) is? Or maybe add a wrapper for allocating below 2G? We might want to use it in other places as well. > cpu->lowcore = lc; > memset(lc, 0, PAGE_SIZE * 2); > sigp_retry(cpu->addr, SIGP_SET_PREFIX, (unsigned long )lc, NULL); (...) I'll pass on reviewing the rest of this patch :)
