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Thu, 22 Oct 2020 16:40:57 +0000 (UTC) Received: from imladris.surriel.com ([96.67.55.152]) by shelob.surriel.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94) (envelope-from ) id 1kVde2-0001c1-45; Thu, 22 Oct 2020 12:40:54 -0400 Message-ID: <62fc8d07474acaccb65a9e20a4ebc0127e417f05.camel@surriel.com> Subject: Re: [PATCH] mm,thp,shmem: limit shmem THP alloc gfp_mask From: Rik van Riel To: Yu Xu , Hugh Dickins Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, Mel Gorman , Andrea Arcangeli , Matthew Wilcox Date: Thu, 22 Oct 2020 12:40:53 -0400 In-Reply-To: References: <20201021234846.5cc97e62@imladris.surriel.com> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-292l4+Z5viPK7NhuvnQt" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: --=-292l4+Z5viPK7NhuvnQt Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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. > >=20 > > 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. > >=20 > > This patch applies the same configurated limitation of THPs to > > shmem > > hugepage allocations, to prevent that from happening. > >=20 > > 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. > >=20 > > Signed-off-by: Rik van Riel > > --- > >=20 > > 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); > > =20 > > +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 =3D !!(vma->vm_flags & VM_HUGEPAGE); > > =20 > > 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; > > =20 > > shmem_pseudo_vma_init(&pvma, info, hindex); > > - page =3D 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 |=3D __GFP_COMP | __GFP_NORETRY | __GFP_NOWARN; > > + gfp &=3D alloc_hugepage_direct_gfpmask(&pvma); >=20 > 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. >=20 > 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. >=20 > 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. --=20 All Rights Reversed. --=-292l4+Z5viPK7NhuvnQt Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEKR73pCCtJ5Xj3yADznnekoTE3oMFAl+RthUACgkQznnekoTE 3oNW0Af/ZErgA5cOrDiHMkRlcH76fPdw8whz+iN9/tqmguNEPBLntOEkULl+gH8n aHiI0F8OIt8oZTWoA4JowhOx1VCadr30XVaiNFym/3audu+Hsh9i8kf4FKGwxxb6 9khP8JubPidppIIBnt8q3TQvnFH/I5J6op2W2DKTs9lNFjxHkVzMpJDVyOm7i0Iq b+7yWS5RtJ2pszvI7T8BDT+UkWdB8Sl6mEC11SWaSGXm6X38viZVixG23PY/ZIl6 G9xoM2YYKcwqmb9aupwJuw2Xwei1q6aCnpTEEZ8eDdu8KLg5czCBjd9pyKZmqqSi gQs/ORiXvPLraSX2sZaLksh1PenTLw== =6hGB -----END PGP SIGNATURE----- --=-292l4+Z5viPK7NhuvnQt--