Hi,
i had multiple memory stalls this weekend again. All kvm processes where
spinning trying to get > 100% CPU and i was not able to even login to
ssh. After 5-10 minutes i was able to login.
There were about 150GB free mem on the host.
Relevant settings (no local storage involved):
vm.dirty_background_ratio:
3
vm.dirty_ratio:
10
vm.min_free_kbytes:
10567004
# cat /sys/kernel/mm/transparent_hugepage/defrag
always defer [defer+madvise] madvise never
# cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never
After that i had the following traces on the host node:
https://pastebin.com/raw/0VhyQmAv
Thanks!
Greets,
Stefan
Am 17.09.2018 um 08:11 schrieb Michal Hocko:
> [sorry I've missed your reply]
>
> On Wed 12-09-18 18:29:25, Mel Gorman wrote:
>> On Wed, Aug 29, 2018 at 09:24:51PM +0200, Michal Hocko wrote:
> [...]
>> I recognise that this fix means that users that expect zone_reclaim_mode==1
>> type behaviour may get burned but the users that benefit from that should
>> also be users that benefit from sizing their workload to a node. They should
>> be able to replicate that with mempolicies or at least use prepation scripts
>> to clear memory on a target node (e.g. membind a memhog to the desired size,
>> exit and then start the target workload).
>
> As I've said in other email. We probably want to add a new mempolicy
> which has zone_reclaim_mode-like semantic.
>
> [...]
>
>>> diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
>>> index 5228c62af416..bac395f1d00a 100644
>>> --- a/include/linux/mempolicy.h
>>> +++ b/include/linux/mempolicy.h
>>> @@ -139,6 +139,8 @@ struct mempolicy *mpol_shared_policy_lookup(struct shared_policy *sp,
>>> struct mempolicy *get_task_policy(struct task_struct *p);
>>> struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
>>> unsigned long addr);
>>> +struct mempolicy *get_vma_policy(struct vm_area_struct *vma,
>>> + unsigned long addr);
>>> bool vma_policy_mof(struct vm_area_struct *vma);
>>>
>>> extern void numa_default_policy(void);
>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>> index c3bc7e9c9a2a..94472bf9a31b 100644
>>> --- a/mm/huge_memory.c
>>> +++ b/mm/huge_memory.c
>>> @@ -629,21 +629,30 @@ 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)
>>> +static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma, unsigned long addr)
>>> {
>>> const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE);
>>> + gfp_t this_node = 0;
>>> + struct mempolicy *pol;
>>> +
>>> +#ifdef CONFIG_NUMA
>>> + /* __GFP_THISNODE makes sense only if there is no explicit binding */
>>> + pol = get_vma_policy(vma, addr);
>>> + if (pol->mode != MPOL_BIND)
>>> + this_node = __GFP_THISNODE;
>>> +#endif
>>>
>>
>> Where is the mpol_cond_put? Historically it might not have mattered
>> because THP could not be used with a shared possibility but it probably
>> matters now that tmpfs can be backed by THP.
>
> http://lkml.kernel.org/r/20180830064732.GA2656@xxxxxxxxxxxxxx
>
>> The comment needs more expansion as well. Arguably it only makes sense in
>> the event we are explicitly bound to one node because if we are bound to
>> two nodes without interleaving then why not fall back? The answer to that
>> is outside the scope of the patch but the comment as-is will cause head
>> scratches in a years time.
>
> Do you have any specific wording in mind? I have a bit hard time to come
> up with something more precise and do not go into details too much.
>
>>> if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, &transparent_hugepage_flags))
>>> - return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY);
>>> + return GFP_TRANSHUGE | (vma_madvised ? 0 : __GFP_NORETRY | this_node);
>>> if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_FLAG, &transparent_hugepage_flags))
>>> - return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM;
>>> + return GFP_TRANSHUGE_LIGHT | __GFP_KSWAPD_RECLAIM | this_node;
>>> if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_KSWAPD_OR_MADV_FLAG, &transparent_hugepage_flags))
>>> return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
>>> - __GFP_KSWAPD_RECLAIM);
>>> + __GFP_KSWAPD_RECLAIM | this_node);
>>> if (test_bit(TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG, &transparent_hugepage_flags))
>>> return GFP_TRANSHUGE_LIGHT | (vma_madvised ? __GFP_DIRECT_RECLAIM :
>>> - 0);
>>> - return GFP_TRANSHUGE_LIGHT;
>>> + this_node);
>>> + return GFP_TRANSHUGE_LIGHT | this_node;
>>> }
>>>
>>> /* Caller must hold page table lock. */
>>> @@ -715,7 +724,7 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
>>> pte_free(vma->vm_mm, pgtable);
>>> return ret;
>>> }
>>> - gfp = alloc_hugepage_direct_gfpmask(vma);
>>> + gfp = alloc_hugepage_direct_gfpmask(vma, haddr);
>>> page = alloc_hugepage_vma(gfp, vma, haddr, HPAGE_PMD_ORDER);
>>> if (unlikely(!page)) {
>>> count_vm_event(THP_FAULT_FALLBACK);
>>> @@ -1290,7 +1299,7 @@ vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
>>> alloc:
>>> if (transparent_hugepage_enabled(vma) &&
>>> !transparent_hugepage_debug_cow()) {
>>> - huge_gfp = alloc_hugepage_direct_gfpmask(vma);
>>> + huge_gfp = alloc_hugepage_direct_gfpmask(vma, haddr);
>>> new_page = alloc_hugepage_vma(huge_gfp, vma, haddr, HPAGE_PMD_ORDER);
>>> } else
>>> new_page = NULL;
>>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>>> index da858f794eb6..75bbfc3d6233 100644
>>> --- a/mm/mempolicy.c
>>> +++ b/mm/mempolicy.c
>>> @@ -1648,7 +1648,7 @@ struct mempolicy *__get_vma_policy(struct vm_area_struct *vma,
>>> * freeing by another task. It is the caller's responsibility to free the
>>> * extra reference for shared policies.
>>> */
>>> -static struct mempolicy *get_vma_policy(struct vm_area_struct *vma,
>>> +struct mempolicy *get_vma_policy(struct vm_area_struct *vma,
>>> unsigned long addr)
>>> {
>>> struct mempolicy *pol = __get_vma_policy(vma, addr);
>>> @@ -2026,32 +2026,6 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
>>> goto out;
>>> }
>>>
>>> - if (unlikely(IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && hugepage)) {
>>> - int hpage_node = node;
>>> -
>>> - /*
>>> - * For hugepage allocation and non-interleave policy which
>>> - * allows the current node (or other explicitly preferred
>>> - * node) we only try to allocate from the current/preferred
>>> - * node and don't fall back to other nodes, as the cost of
>>> - * remote accesses would likely offset THP benefits.
>>> - *
>>> - * If the policy is interleave, or does not allow the current
>>> - * node in its nodemask, we allocate the standard way.
>>> - */
>>> - if (pol->mode == MPOL_PREFERRED &&
>>> - !(pol->flags & MPOL_F_LOCAL))
>>> - hpage_node = pol->v.preferred_node;
>>> -
>>> - nmask = policy_nodemask(gfp, pol);
>>> - if (!nmask || node_isset(hpage_node, *nmask)) {
>>> - mpol_cond_put(pol);
>>> - page = __alloc_pages_node(hpage_node,
>>> - gfp | __GFP_THISNODE, order);
>>> - goto out;
>>> - }
>>> - }
>>> -
>>
>> The hugepage flag passed into this function is now redundant and that
>> means that callers of alloc_hugepage_vma need to move back to using
>> alloc_pages_vma() directly and remove the API entirely. This block of
>> code is about both GFP flag settings and node selection but at a glance I
>> cannot see the point of it because it's very similar to the base page code.
>> The whole point may be to get around the warning in policy_node and that
>> could just as easily be side-stepped in alloc_hugepage_direct_gfpmask
>> as you do already in this patch. There should be no reason why THP has a
>> different policy than a base page within a single VMA.
>
> OK, I can follow up with a cleanup patch once we settle down with this
> approach to fix the issue.
>
> Thanks!
>
