On Thu 28-04-16 17:19:21, Michal Hocko wrote:
> On Wed 27-04-16 14:17:20, Andrew Morton wrote:
> [...]
> > @@ -2484,7 +2485,14 @@ static void collapse_huge_page(struct mm
> > goto out;
> > }
> >
> > - __collapse_huge_page_swapin(mm, vma, address, pmd);
> > + swap = get_mm_counter(mm, MM_SWAPENTS);
> > + curr_allocstall = sum_vm_event(ALLOCSTALL);
> > + /*
> > + * When system under pressure, don't swapin readahead.
> > + * So that avoid unnecessary resource consuming.
> > + */
> > + if (allocstall == curr_allocstall && swap != 0)
> > + __collapse_huge_page_swapin(mm, vma, address, pmd);
> >
> > anon_vma_lock_write(vma->anon_vma);
> >
>
> I have mentioned that before already but this seems like a rather weak
> heuristic. Don't we really rather teach __collapse_huge_page_swapin
> (resp. do_swap_page) do to an optimistic GFP_NOWAIT allocations and
> back off under the memory pressure?
I gave it a try and it doesn't seem really bad. Untested and I might
have missed something really obvious but what do you think about this
approach rather than relying on ALLOCSTALL which is really weak
heuristic:
---
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 87f09dc986ab..1a4d4c807d92 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2389,7 +2389,8 @@ static void __collapse_huge_page_swapin(struct mm_struct *mm,
swapped_in++;
ret = do_swap_page(mm, vma, _address, pte, pmd,
FAULT_FLAG_ALLOW_RETRY|FAULT_FLAG_RETRY_NOWAIT,
- pteval);
+ pteval,
+ GFP_HIGHUSER_MOVABLE | ~__GFP_DIRECT_RECLAIM);
if (ret & VM_FAULT_ERROR) {
trace_mm_collapse_huge_page_swapin(mm, swapped_in, 0);
return;
diff --git a/mm/memory.c b/mm/memory.c
index d79c6db41502..f897ec89bd79 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2490,7 +2490,7 @@ EXPORT_SYMBOL(unmap_mapping_range);
*/
int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pte_t *page_table, pmd_t *pmd,
- unsigned int flags, pte_t orig_pte)
+ unsigned int flags, pte_t orig_pte, gfp_t gfp_mask)
{
spinlock_t *ptl;
struct page *page, *swapcache;
@@ -2519,8 +2519,7 @@ int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
delayacct_set_flag(DELAYACCT_PF_SWAPIN);
page = lookup_swap_cache(entry);
if (!page) {
- page = swapin_readahead(entry,
- GFP_HIGHUSER_MOVABLE, vma, address);
+ page = swapin_readahead(entry, gfp_mask, vma, address);
if (!page) {
/*
* Back out if somebody else faulted in this pte
@@ -2573,7 +2572,7 @@ int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
goto out_page;
}
- if (mem_cgroup_try_charge(page, mm, GFP_KERNEL, &memcg, false)) {
+ if (mem_cgroup_try_charge(page, mm, gfp_mask, &memcg, false)) {
ret = VM_FAULT_OOM;
goto out_page;
}
@@ -3349,7 +3348,7 @@ static int handle_pte_fault(struct mm_struct *mm,
flags, entry);
}
return do_swap_page(mm, vma, address,
- pte, pmd, flags, entry);
+ pte, pmd, flags, entry, GFP_HIGHUSER_MOVABLE);
}
if (pte_protnone(entry))
--
Michal Hocko
SUSE Labs
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