Am 28.08.2018 um 10:18 schrieb Michal Hocko: > [CC Stefan Priebe who has reported the same/similar issue on openSUSE > mailing list recently - the thread starts http://lkml.kernel.org/r/20180820032204.9591-1-aarcange@xxxxxxxxxx] > > On Tue 28-08-18 09:53:21, Michal Hocko wrote: >> On Thu 23-08-18 12:52:53, Michal Hocko wrote: >>> On Wed 22-08-18 11:52:50, Andrea Arcangeli wrote: >>>> On Wed, Aug 22, 2018 at 11:02:14AM +0200, Michal Hocko wrote: >>> [...] >>>>> I still have to digest the __GFP_THISNODE thing but I _think_ that the >>>>> alloc_pages_vma code is just trying to be overly clever and >>>>> __GFP_THISNODE is not a good fit for it. >>>> >>>> My option 2 did just that, it removed __GFP_THISNODE but only for >>>> MADV_HUGEPAGE and in general whenever reclaim was activated by >>>> __GFP_DIRECT_RECLAIM. That is also signal that the user really wants >>>> THP so then it's less bad to prefer THP over NUMA locality. >>>> >>>> For the default which is tuned for short lived allocation, preferring >>>> local memory is most certainly better win for short lived allocation >>>> where THP can't help much, this is why I didn't remove __GFP_THISNODE >>>> from the default defrag policy. >>> >>> Yes I agree. >> >> I finally got back to this again. I have checked your patch and I am >> really wondering whether alloc_pages_vma is really the proper place to >> play these tricks. We already have that mind blowing alloc_hugepage_direct_gfpmask >> and it should be the proper place to handle this special casing. So what >> do you think about the following. It should be essentially the same >> thing. Aka use __GFP_THIS_NODE only when we are doing an optimistic THP >> allocation. Madvise signalizes you know what you are doing and THP has >> the top priority. If you care enough about the numa placement then you >> should better use mempolicy. > > Now the patch is still untested but it compiles at least. Great - i recompiled the SLES15 kernel with that one applied and will test if it helps. Stefan > --- > From 88e0ca4c9c403c6046f1c47d5ee17548f9dc841a Mon Sep 17 00:00:00 2001 > From: Michal Hocko <mhocko@xxxxxxxx> > Date: Tue, 28 Aug 2018 09:59:19 +0200 > Subject: [PATCH] mm, thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings > > Andrea has noticed [1] that a THP allocation might be really disruptive > when allocated on NUMA system with the local node full or hard to > reclaim. Stefan has posted an allocation stall report on 4.12 based > SLES kernel which suggests the same issue: > [245513.362669] kvm: page allocation stalls for 194572ms, order:9, mode:0x4740ca(__GFP_HIGHMEM|__GFP_IO|__GFP_FS|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_THISNODE|__GFP_MOVABLE|__GFP_DIRECT_RECLAIM), nodemask=(null) > [245513.363983] kvm cpuset=/ mems_allowed=0-1 > [245513.364604] CPU: 10 PID: 84752 Comm: kvm Tainted: G W 4.12.0+98-phSLE15 (unreleased) > [245513.365258] Hardware name: Supermicro SYS-1029P-WTRT/X11DDW-NT, BIOS 2.0 12/05/2017 > [245513.365905] Call Trace: > [245513.366535] dump_stack+0x5c/0x84 > [245513.367148] warn_alloc+0xe0/0x180 > [245513.367769] __alloc_pages_slowpath+0x820/0xc90 > [245513.368406] ? __slab_free+0xa9/0x2f0 > [245513.369048] ? __slab_free+0xa9/0x2f0 > [245513.369671] __alloc_pages_nodemask+0x1cc/0x210 > [245513.370300] alloc_pages_vma+0x1e5/0x280 > [245513.370921] do_huge_pmd_wp_page+0x83f/0xf00 > [245513.371554] ? set_huge_zero_page.isra.52.part.53+0x9b/0xb0 > [245513.372184] ? do_huge_pmd_anonymous_page+0x631/0x6d0 > [245513.372812] __handle_mm_fault+0x93d/0x1060 > [245513.373439] handle_mm_fault+0xc6/0x1b0 > [245513.374042] __do_page_fault+0x230/0x430 > [245513.374679] ? get_vtime_delta+0x13/0xb0 > [245513.375411] do_page_fault+0x2a/0x70 > [245513.376145] ? page_fault+0x65/0x80 > [245513.376882] page_fault+0x7b/0x80 > [...] > [245513.382056] Mem-Info: > [245513.382634] active_anon:126315487 inactive_anon:1612476 isolated_anon:5 > active_file:60183 inactive_file:245285 isolated_file:0 > unevictable:15657 dirty:286 writeback:1 unstable:0 > slab_reclaimable:75543 slab_unreclaimable:2509111 > mapped:81814 shmem:31764 pagetables:370616 bounce:0 > free:32294031 free_pcp:6233 free_cma:0 > [245513.386615] Node 0 active_anon:254680388kB inactive_anon:1112760kB active_file:240648kB inactive_file:981168kB unevictable:13368kB isolated(anon):0kB isolated(file):0kB mapped:280240kB dirty:1144kB writeback:0kB shmem:95832kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 81225728kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no > [245513.388650] Node 1 active_anon:250583072kB inactive_anon:5337144kB active_file:84kB inactive_file:0kB unevictable:49260kB isolated(anon):20kB isolated(file):0kB mapped:47016kB dirty:0kB writeback:4kB shmem:31224kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 31897600kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no > > The defrag mode is "madvise" and from the above report it is clear that > the THP has been allocated for MADV_HUGEPAGA vma. > > Andrea has identified that the main source of the problem is > __GFP_THISNODE usage: > > : The problem is that direct compaction combined with the NUMA > : __GFP_THISNODE logic in mempolicy.c is telling reclaim to swap very > : hard the local node, instead of failing the allocation if there's no > : THP available in the local node. > : > : Such logic was ok until __GFP_THISNODE was added to the THP allocation > : path even with MPOL_DEFAULT. > : > : The idea behind the __GFP_THISNODE addition, is that it is better to > : provide local memory in PAGE_SIZE units than to use remote NUMA THP > : backed memory. That largely depends on the remote latency though, on > : threadrippers for example the overhead is relatively low in my > : experience. > : > : The combination of __GFP_THISNODE and __GFP_DIRECT_RECLAIM results in > : extremely slow qemu startup with vfio, if the VM is larger than the > : size of one host NUMA node. This is because it will try very hard to > : unsuccessfully swapout get_user_pages pinned pages as result of the > : __GFP_THISNODE being set, instead of falling back to PAGE_SIZE > : allocations and instead of trying to allocate THP on other nodes (it > : would be even worse without vfio type1 GUP pins of course, except it'd > : be swapping heavily instead). > > Fix this by removing __GFP_THISNODE handling from alloc_pages_vma where > it doesn't belong and move it to alloc_hugepage_direct_gfpmask where we > juggle gfp flags for different allocation modes. The rationale is that > __GFP_THISNODE is helpful in relaxed defrag modes because falling back > to a different node might be more harmful than the benefit of a large page. > If the user really requires THP (e.g. by MADV_HUGEPAGE) then the THP has > a higher priority than local NUMA placement. The later might be controlled > via NUMA policies to be more fine grained. > > [1] http://lkml.kernel.org/r/20180820032204.9591-1-aarcange@xxxxxxxxxx > > Fixes: 5265047ac301 ("mm, thp: really limit transparent hugepage allocation to local node") > Reported-by: Stefan Priebe <s.priebe@xxxxxxxxxxxx> > Debugged-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > --- > mm/huge_memory.c | 10 +++++----- > mm/mempolicy.c | 26 -------------------------- > 2 files changed, 5 insertions(+), 31 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index c3bc7e9c9a2a..a703c23f8bab 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -634,16 +634,16 @@ static inline gfp_t alloc_hugepage_direct_gfpmask(struct vm_area_struct *vma) > const bool vma_madvised = !!(vma->vm_flags & VM_HUGEPAGE); > > 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 | __GFP_THISNODE); > 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 | __GFP_THISNODE; > 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 | __GFP_THISNODE); > 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; > + __GFP_THISNODE); > + return GFP_TRANSHUGE_LIGHT | __GFP_THISNODE; > } > > /* Caller must hold page table lock. */ > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index da858f794eb6..9f0800885613 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -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; > - } > - } > - > nmask = policy_nodemask(gfp, pol); > preferred_nid = policy_node(gfp, pol, node); > page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask); >
