mm,thp,shmem: limit shmem THP alloc gfp_mask

Patch series "mm,thp,shm: limit shmem THP alloc gfp_mask", v6.

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.

With this patch applied, THP allocations for tmpfs will be a little more
aggressive than today for files mmapped with MADV_HUGEPAGE, and a little
less aggressive for files that are not mmapped or mapped without that
flag.

This patch (of 3):

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.

Controlling the gfp_mask of THP allocations through the knobs in sysfs
allows users to determine the balance between how aggressively the system
tries to allocate THPs at fault time, and how much the application may end
up stalling attempting those allocations.

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.

With this patch applied, THP allocations for tmpfs will be a little more
aggressive than today for files mmapped with MADV_HUGEPAGE, and a little
less aggressive for files that are not mmapped or mapped without that
flag.

Link: https://lkml.kernel.org/r/20201124194925.623931-1-riel@surriel.com
Link: https://lkml.kernel.org/r/20201124194925.623931-2-riel@surriel.com
Signed-off-by: Rik van Riel <riel@surriel.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Xu Yu <xuyu@linux.alibaba.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 6e479e9c48cebe6aca409a9d49d98cd3351f1785..53caa98468546b0876d6a6d34d81cc0d633920cc 100644 (file)
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -612,6 +612,8 @@ 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 vma_thp_gfp_mask(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 a7f47e39935c9c21ace5ccb76743ba53076c187f..5aa045e3b5dc19046752f8370bde03e2763311a0 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -664,9 +664,9 @@ release:
  *         available
  * never: never stall for any thp allocation
  */
-static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma)
+gfp_t vma_thp_gfp_mask(struct vm_area_struct *vma)
 {
-       const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
+       const bool vma_madvised = vma && (vma->vm_flags & VM_HUGEPAGE);
 
        /* Always do synchronous compaction */
        if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
@@ -759,7 +759,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
                }
                return ret;
        }
-       gfp = alloc_hugepage_direct_gfpmask(vma);
+       gfp = vma_thp_gfp_mask(vma);
        page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
        if (unlikely(!page)) {
                count_vm_event(THP_FAULT_FALLBACK);

diff --git a/mm/shmem.c b/mm/shmem.c
index 168dc127424164b16201d3a5ab64d568e5926b4e..8414f12ac05cf206084c88ad216df59a3e5a8da0 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1517,8 +1517,8 @@ 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);
+       page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER, &pvma, 0, numa_node_id(),
+                              true);
        shmem_pseudo_vma_destroy(&pvma);
        if (page)
                prep_transhuge_page(page);
@@ -1774,6 +1774,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
        struct page *page;
        enum sgp_type sgp_huge = sgp;
        pgoff_t hindex = index;
+       gfp_t huge_gfp;
        int error;
        int once = 0;
        int alloced = 0;
@@ -1860,7 +1861,8 @@ repeat:
        }
 
 alloc_huge:
-       page = shmem_alloc_and_acct_page(gfp, inode, index, true);
+       huge_gfp = vma_thp_gfp_mask(vma);
+       page = shmem_alloc_and_acct_page(huge_gfp, inode, index, true);
        if (IS_ERR(page)) {
 alloc_nohuge:
                page = shmem_alloc_and_acct_page(gfp, inode,