| Message ID | 20210127101813.6370-2-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/cma: better error handling and count pages per zone | expand |
On 27 Jan 2021, at 5:18, David Hildenbrand wrote: > Right now, if activation fails, we might already have exposed some pages to > the buddy for CMA use (although they will never get actually used by CMA), > and some pages won't be exposed to the buddy at all. > > Let's check for "single zone" early and on error, don't expose any pages > for CMA use - instead, expose them to the buddy available for any use. > Simply call free_reserved_page() on every single page - easier than > going via free_reserved_area(), converting back and forth between pfns > and virt addresses. > > In addition, make sure to fixup totalcma_pages properly. > > Example: 6 GiB QEMU VM with "... hugetlb_cma=2G movablecore=20% ...": > [ 0.006891] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node > [ 0.006893] cma: Reserved 2048 MiB at 0x0000000100000000 > [ 0.006893] hugetlb_cma: reserved 2048 MiB on node 0 > ... > [ 0.175433] cma: CMA area hugetlb0 could not be activated > > Before this patch: > # cat /proc/meminfo > MemTotal: 5867348 kB > MemFree: 5692808 kB > MemAvailable: 5542516 kB > ... > CmaTotal: 2097152 kB > CmaFree: 1884160 kB > > After this patch: > # cat /proc/meminfo > MemTotal: 6077308 kB > MemFree: 5904208 kB > MemAvailable: 5747968 kB > ... > CmaTotal: 0 kB > CmaFree: 0 kB > > Note: cma_init_reserved_mem() makes sure that we always cover full > pageblocks / MAX_ORDER - 1 pages. > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> > Cc: Mike Rapoport <rppt@kernel.org> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Wei Yang <richard.weiyang@linux.alibaba.com> > Signed-off-by: David Hildenbrand <david@redhat.com> > --- > mm/cma.c | 43 +++++++++++++++++++++---------------------- > 1 file changed, 21 insertions(+), 22 deletions(-) LGTM. Reviewed-by: Zi Yan <ziy@nvidia.com> — Best Regards, Yan Zi
On Wed, Jan 27, 2021 at 11:18:12AM +0100, David Hildenbrand wrote: > Right now, if activation fails, we might already have exposed some pages to > the buddy for CMA use (although they will never get actually used by CMA), > and some pages won't be exposed to the buddy at all. > > Let's check for "single zone" early and on error, don't expose any pages > for CMA use - instead, expose them to the buddy available for any use. > Simply call free_reserved_page() on every single page - easier than > going via free_reserved_area(), converting back and forth between pfns > and virt addresses. > > In addition, make sure to fixup totalcma_pages properly. > > Example: 6 GiB QEMU VM with "... hugetlb_cma=2G movablecore=20% ...": > [ 0.006891] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node > [ 0.006893] cma: Reserved 2048 MiB at 0x0000000100000000 > [ 0.006893] hugetlb_cma: reserved 2048 MiB on node 0 > ... > [ 0.175433] cma: CMA area hugetlb0 could not be activated > > Before this patch: > # cat /proc/meminfo > MemTotal: 5867348 kB > MemFree: 5692808 kB > MemAvailable: 5542516 kB > ... > CmaTotal: 2097152 kB > CmaFree: 1884160 kB > > After this patch: > # cat /proc/meminfo > MemTotal: 6077308 kB > MemFree: 5904208 kB > MemAvailable: 5747968 kB > ... > CmaTotal: 0 kB > CmaFree: 0 kB > > Note: cma_init_reserved_mem() makes sure that we always cover full > pageblocks / MAX_ORDER - 1 pages. > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> > Cc: Mike Rapoport <rppt@kernel.org> > Cc: Oscar Salvador <osalvador@suse.de> > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Wei Yang <richard.weiyang@linux.alibaba.com> > Signed-off-by: David Hildenbrand <david@redhat.com> Besides benefit of the error handling, I find this code much more cleaer: Reviewed-by: Oscar Salvador <osalvador@suse.de>
diff --git a/mm/cma.c b/mm/cma.c index 0ba69cd16aeb..23d4a97c834a 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -94,34 +94,29 @@ static void cma_clear_bitmap(struct cma *cma, unsigned long pfn, static void __init cma_activate_area(struct cma *cma) { - unsigned long base_pfn = cma->base_pfn, pfn = base_pfn; - unsigned i = cma->count >> pageblock_order; + unsigned long base_pfn = cma->base_pfn, pfn; struct zone *zone; cma->bitmap = bitmap_zalloc(cma_bitmap_maxno(cma), GFP_KERNEL); if (!cma->bitmap) goto out_error; - WARN_ON_ONCE(!pfn_valid(pfn)); - zone = page_zone(pfn_to_page(pfn)); - - do { - unsigned j; - - base_pfn = pfn; - for (j = pageblock_nr_pages; j; --j, pfn++) { - WARN_ON_ONCE(!pfn_valid(pfn)); - /* - * alloc_contig_range requires the pfn range - * specified to be in the same zone. Make this - * simple by forcing the entire CMA resv range - * to be in the same zone. - */ - if (page_zone(pfn_to_page(pfn)) != zone) - goto not_in_zone; - } - init_cma_reserved_pageblock(pfn_to_page(base_pfn)); - } while (--i); + /* + * alloc_contig_range() requires the pfn range specified to be in the + * same zone. Simplify by forcing the entire CMA resv range to be in the + * same zone. + */ + WARN_ON_ONCE(!pfn_valid(base_pfn)); + zone = page_zone(pfn_to_page(base_pfn)); + for (pfn = base_pfn + 1; pfn < base_pfn + cma->count; pfn++) { + WARN_ON_ONCE(!pfn_valid(pfn)); + if (page_zone(pfn_to_page(pfn)) != zone) + goto not_in_zone; + } + + for (pfn = base_pfn; pfn < base_pfn + cma->count; + pfn += pageblock_nr_pages) + init_cma_reserved_pageblock(pfn_to_page(pfn)); mutex_init(&cma->lock); @@ -135,6 +130,10 @@ static void __init cma_activate_area(struct cma *cma) not_in_zone: bitmap_free(cma->bitmap); out_error: + /* Expose all pages to the buddy, they are useless for CMA. */ + for (pfn = base_pfn; pfn < base_pfn + cma->count; pfn++) + free_reserved_page(pfn_to_page(pfn)); + totalcma_pages -= cma->count; cma->count = 0; pr_err("CMA area %s could not be activated\n", cma->name); return;
Right now, if activation fails, we might already have exposed some pages to the buddy for CMA use (although they will never get actually used by CMA), and some pages won't be exposed to the buddy at all. Let's check for "single zone" early and on error, don't expose any pages for CMA use - instead, expose them to the buddy available for any use. Simply call free_reserved_page() on every single page - easier than going via free_reserved_area(), converting back and forth between pfns and virt addresses. In addition, make sure to fixup totalcma_pages properly. Example: 6 GiB QEMU VM with "... hugetlb_cma=2G movablecore=20% ...": [ 0.006891] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node [ 0.006893] cma: Reserved 2048 MiB at 0x0000000100000000 [ 0.006893] hugetlb_cma: reserved 2048 MiB on node 0 ... [ 0.175433] cma: CMA area hugetlb0 could not be activated Before this patch: # cat /proc/meminfo MemTotal: 5867348 kB MemFree: 5692808 kB MemAvailable: 5542516 kB ... CmaTotal: 2097152 kB CmaFree: 1884160 kB After this patch: # cat /proc/meminfo MemTotal: 6077308 kB MemFree: 5904208 kB MemAvailable: 5747968 kB ... CmaTotal: 0 kB CmaFree: 0 kB Note: cma_init_reserved_mem() makes sure that we always cover full pageblocks / MAX_ORDER - 1 pages. Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Mike Rapoport <rppt@kernel.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@kernel.org> Cc: Wei Yang <richard.weiyang@linux.alibaba.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/cma.c | 43 +++++++++++++++++++++---------------------- 1 file changed, 21 insertions(+), 22 deletions(-)