On Fri, 2020-10-23 at 00:00 +0800, Yu Xu wrote: > On 10/22/20 11:48 AM, Rik van Riel wrote: > > The allocation flags of anonymous transparent huge pages can be > > controlled > > through the files in /sys/kernel/mm/transparent_hugepage/defrag, > > which can > > help the system from getting bogged down in the page reclaim and > > compaction > > code when many THPs are getting allocated simultaneously. > > > > However, the gfp_mask for shmem THP allocations were not limited by > > those > > configuration settings, and some workloads ended up with all CPUs > > stuck > > on the LRU lock in the page reclaim code, trying to allocate dozens > > of > > THPs simultaneously. > > > > This patch applies the same configurated limitation of THPs to > > shmem > > hugepage allocations, to prevent that from happening. > > > > This way a THP defrag setting of "never" or "defer+madvise" will > > result > > in quick allocation failures without direct reclaim when no 2MB > > free > > pages are available. > > > > Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx> > > --- > > > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > > index c603237e006c..0a5b164a26d9 100644 > > --- a/include/linux/gfp.h > > +++ b/include/linux/gfp.h > > @@ -614,6 +614,8 @@ bool gfp_pfmemalloc_allowed(gfp_t gfp_mask); > > extern void pm_restrict_gfp_mask(void); > > extern void pm_restore_gfp_mask(void); > > > > +extern gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct > > *vma); > > + > > #ifdef CONFIG_PM_SLEEP > > extern bool pm_suspended_storage(void); > > #else > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 9474dbc150ed..9b08ce5cc387 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -649,7 +649,7 @@ static vm_fault_t > > __do_huge_pmd_anonymous_page(struct vm_fault *vmf, > > * available > > * never: never stall for any thp allocation > > */ > > -static inline gfp_t alloc_hugepage_direct_gfpmask(struct > > vm_area_struct *vma) > > +gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) > > { > > const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE); > > > > diff --git a/mm/shmem.c b/mm/shmem.c > > index 537c137698f8..d1290eb508e5 100644 > > --- a/mm/shmem.c > > +++ b/mm/shmem.c > > @@ -1545,8 +1545,11 @@ static struct page > > *shmem_alloc_hugepage(gfp_t gfp, > > return NULL; > > > > shmem_pseudo_vma_init(&pvma, info, hindex); > > - page = alloc_pages_vma(gfp | __GFP_COMP | __GFP_NORETRY | > > __GFP_NOWARN, > > - HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(), > > true); > > + /* Limit the gfp mask according to THP configuration. */ > > + gfp |= __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN; > > + gfp &= alloc_hugepage_direct_gfpmask(&pvma); > > It is fine to reuse `alloc_hugepage_direct_gfpmask`, but > `pvma.vm_flags & VM_HUGEPAGE` is always false here, thus, > `vma_madvised` in `alloc_hugepage_direct_gfpmask` will always > be false. > > That is why I chose to do the gfp_mask fixup in `shmem_getpage_gfp`, > using `sgp_huge` to indicate `vma_madvised`, although with some silly > mistakes pointed out by you, in another mail thread. > > It will be better if vma_madvised is well handled in your solution. OK, let me send a v2 that does that! By just passing a correct gfp_mask to shmem_alloc_and_acct_page we can also avoid the gfp gymnastics in shmem_alloc_hugepage that Michal rightfully objected to. -- All Rights Reversed.
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