On Thu, 2019-08-15 at 09:36 +0200, christophe leroy wrote: > > Le 15/08/2019 à 06:10, Alastair D'Silva a écrit : > > From: Alastair D'Silva <alast...@d-silva.org> > > > > When presented with large amounts of memory being hotplugged > > (in my test case, ~890GB), the call to flush_dcache_range takes > > a while (~50 seconds), triggering RCU stalls. > > > > This patch breaks up the call into 16GB chunks, calling > > cond_resched() inbetween to allow the scheduler to run. > > Is 16GB small enough ? If 890GB takes 50s, 16GB still takes about 1s. > I'd use 1GB chuncks to remain below 100ms. > > > Signed-off-by: Alastair D'Silva <alast...@d-silva.org> > > --- > > arch/powerpc/mm/mem.c | 16 ++++++++++++++-- > > 1 file changed, 14 insertions(+), 2 deletions(-) > > > > diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c > > index 5400da87a804..fb0d5e9aa11b 100644 > > --- a/arch/powerpc/mm/mem.c > > +++ b/arch/powerpc/mm/mem.c > > @@ -104,11 +104,14 @@ int __weak remove_section_mapping(unsigned > > long start, unsigned long end) > > return -ENODEV; > > } > > > > +#define FLUSH_CHUNK_SIZE (16ull * 1024ull * 1024ull * 1024ull) > > Can we use SZ_16GB ? Sure, I'll go with 1GB as you recommended above
> > + > > int __ref arch_add_memory(int nid, u64 start, u64 size, > > struct mhp_restrictions *restrictions) > > { > > unsigned long start_pfn = start >> PAGE_SHIFT; > > unsigned long nr_pages = size >> PAGE_SHIFT; > > + unsigned long i; > > int rc; > > > > resize_hpt_for_hotplug(memblock_phys_mem_size()); > > @@ -120,7 +123,11 @@ int __ref arch_add_memory(int nid, u64 start, > > u64 size, > > start, start + size, rc); > > return -EFAULT; > > } > > - flush_dcache_range(start, start + size); > > + > > + for (i = 0; i < size; i += FLUSH_CHUNK_SIZE) { > > + flush_dcache_range(start + i, min(start + size, start + > > i + FLUSH_CHUNK_SIZE)); > > Isn't the line a bit long (I have not checked). > > > + cond_resched(); > > + } > > > > return __add_pages(nid, start_pfn, nr_pages, restrictions); > > } > > @@ -131,13 +138,18 @@ void __ref arch_remove_memory(int nid, u64 > > start, u64 size, > > unsigned long start_pfn = start >> PAGE_SHIFT; > > unsigned long nr_pages = size >> PAGE_SHIFT; > > struct page *page = pfn_to_page(start_pfn) + > > vmem_altmap_offset(altmap); > > + unsigned long i; > > int ret; > > > > __remove_pages(page_zone(page), start_pfn, nr_pages, altmap); > > > > /* Remove htab bolted mappings for this section of memory */ > > start = (unsigned long)__va(start); > > - flush_dcache_range(start, start + size); > > + for (i = 0; i < size; i += FLUSH_CHUNK_SIZE) { > > + flush_dcache_range(start + i, min(start + size, start + > > i + FLUSH_CHUNK_SIZE)); > > + cond_resched(); > > + } > > + > > ret = remove_section_mapping(start, start + size); > > WARN_ON_ONCE(ret); > > > > > > Christophe > > --- > L'absence de virus dans ce courrier électronique a été vérifiée par > le logiciel antivirus Avast. > https://urldefense.proofpoint.com/v2/url?u=https-3A__www.avast.com_antivirus&d=DwIDaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=cT4tgeEQ0Ll3SIlZDHE5AEXyKy6uKADMtf9_Eb7-vec&m=TBT2NNM2DXqDWHhSb_WdFPcfAjYk9hP2cvGksF001cQ&s=XURKAOQQ4h3_RhJlezSguD2kpSitAF-uBhQqVZLU4GU&e= > > -- Alastair D'Silva Open Source Developer Linux Technology Centre, IBM Australia mob: 0423 762 819