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Shutemov" CC: "linux-mm@kvack.org" , "linux-fsdevel@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "matthew.wilcox@oracle.com" , "kirill.shutemov@linux.intel.com" , Kernel Team , "william.kucharski@oracle.com" , "akpm@linux-foundation.org" , "hdanton@sina.com" Subject: Re: [PATCH v7 5/6] mm,thp: add read-only THP support for (non-shmem) FS Thread-Topic: [PATCH v7 5/6] mm,thp: add read-only THP support for (non-shmem) FS Thread-Index: AQHVKYdGAmz09KUZ80Kts9GVGsmXGaaqwvwAgAAUeoA= Date: Mon, 24 Jun 2019 14:01:05 +0000 Message-ID: <52BDA50B-7CBF-4333-9D15-0C17FD04F6ED@fb.com> References: <20190623054749.4016638-1-songliubraving@fb.com> <20190623054749.4016638-6-songliubraving@fb.com> <20190624124746.7evd2hmbn3qg3tfs@box> In-Reply-To: <20190624124746.7evd2hmbn3qg3tfs@box> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3445.104.11) x-originating-ip: [2620:10d:c090:180::1:d642] x-ms-publictraffictype: Email x-ms-office365-filtering-correlation-id: 569c225a-65e3-42ae-b43b-08d6f8ac665a x-microsoft-antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(1401327)(2017052603328)(7193020);SRVR:MWHPR15MB1853; x-ms-traffictypediagnostic: MWHPR15MB1853: x-microsoft-antispam-prvs: x-ms-oob-tlc-oobclassifiers: OLM:9508; x-forefront-prvs: 007814487B x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(376002)(366004)(39860400002)(396003)(346002)(136003)(199004)(189003)(6512007)(53546011)(6506007)(2906002)(50226002)(316002)(102836004)(76176011)(99286004)(54906003)(7736002)(68736007)(478600001)(71190400001)(71200400001)(76116006)(81166006)(6436002)(66556008)(66476007)(305945005)(66446008)(66946007)(4326008)(86362001)(25786009)(5660300002)(8676002)(6916009)(6116002)(81156014)(8936002)(14454004)(33656002)(73956011)(57306001)(486006)(64756008)(256004)(186003)(14444005)(11346002)(46003)(446003)(2616005)(476003)(229853002)(36756003)(6486002)(53936002)(6246003)(142933001);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR15MB1853;H:MWHPR15MB1165.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;A:1;MX:1; received-spf: None (protection.outlook.com: fb.com does not designate permitted sender hosts) x-ms-exchange-senderadcheck: 1 x-microsoft-antispam-message-info: FQn27IbcXnj326Zn8r9r/sYKCz5HR1Od4yavvLcuKmEoAbg+O3FLXLig3D2QdeOtU5nNWa+qs7EQxwMcFeCiZl5MGMEcOn46zARax7Pyi2TCelW+doJyfMH+kTVFe4cqgVl2I474u7xPzRIOTTzUsSC+Pt448VfOWYA0jJj8OL2Bgcyhb+vDa5KWNGRIzEhNKALMOAclRs84RdXNETiqPhw5bdKfuV2iVjdkkb+xVJlPztjjDXJxULCUsGMtjFkr1NM4wtGjlbk6wVs0sW0+cLix/8p0yfocSr9j4YvLBTSxb/3IAb4JjjEY1f/prhv0qb2Gd9xkKmt9uQEw9YTAhEDQOxUWKKXFmVV1+lPnVzpjFTgtUxzLPZ5nS8jjw/EzvMOaLA7y/vWrN02Ew6Y5hzUPBu3cii+UVSjTRWnseaM= Content-Type: text/plain; charset="us-ascii" Content-ID: <6FFB1DDE0C11C44FA14633B7588DE2C1@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 569c225a-65e3-42ae-b43b-08d6f8ac665a X-MS-Exchange-CrossTenant-originalarrivaltime: 24 Jun 2019 14:01:05.3646 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: songliubraving@fb.com X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR15MB1853 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-24_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906240114 X-FB-Internal: deliver 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: > On Jun 24, 2019, at 5:47 AM, Kirill A. Shutemov wr= ote: >=20 > On Sat, Jun 22, 2019 at 10:47:48PM -0700, Song Liu wrote: >> This patch is (hopefully) the first step to enable THP for non-shmem >> filesystems. >>=20 >> This patch enables an application to put part of its text sections to TH= P >> via madvise, for example: >>=20 >> madvise((void *)0x600000, 0x200000, MADV_HUGEPAGE); >>=20 >> We tried to reuse the logic for THP on tmpfs. >>=20 >> Currently, write is not supported for non-shmem THP. khugepaged will onl= y >> process vma with VM_DENYWRITE. The next patch will handle writes, which >> would only happen when the vma with VM_DENYWRITE is unmapped. >>=20 >> An EXPERIMENTAL config, READ_ONLY_THP_FOR_FS, is added to gate this >> feature. >>=20 >> Acked-by: Rik van Riel >> Signed-off-by: Song Liu >> --- >> mm/Kconfig | 11 ++++++ >> mm/filemap.c | 4 +-- >> mm/khugepaged.c | 90 ++++++++++++++++++++++++++++++++++++++++--------- >> mm/rmap.c | 12 ++++--- >> 4 files changed, 96 insertions(+), 21 deletions(-) >>=20 >> diff --git a/mm/Kconfig b/mm/Kconfig >> index f0c76ba47695..0a8fd589406d 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -762,6 +762,17 @@ config GUP_BENCHMARK >>=20 >> See tools/testing/selftests/vm/gup_benchmark.c >>=20 >> +config READ_ONLY_THP_FOR_FS >> + bool "Read-only THP for filesystems (EXPERIMENTAL)" >> + depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM >> + >> + help >> + Allow khugepaged to put read-only file-backed pages in THP. >> + >> + This is marked experimental because it is a new feature. Write >> + support of file THPs will be developed in the next few release >> + cycles. >> + >> config ARCH_HAS_PTE_SPECIAL >> bool >>=20 >> diff --git a/mm/filemap.c b/mm/filemap.c >> index 5f072a113535..e79ceccdc6df 100644 >> --- a/mm/filemap.c >> +++ b/mm/filemap.c >> @@ -203,8 +203,8 @@ static void unaccount_page_cache_page(struct address= _space *mapping, >> __mod_node_page_state(page_pgdat(page), NR_SHMEM, -nr); >> if (PageTransHuge(page)) >> __dec_node_page_state(page, NR_SHMEM_THPS); >> - } else { >> - VM_BUG_ON_PAGE(PageTransHuge(page), page); >> + } else if (PageTransHuge(page)) { >> + __dec_node_page_state(page, NR_FILE_THPS); >> } >>=20 >> /* >> diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> index 158cad542627..090127e4e185 100644 >> --- a/mm/khugepaged.c >> +++ b/mm/khugepaged.c >> @@ -48,6 +48,7 @@ enum scan_result { >> SCAN_CGROUP_CHARGE_FAIL, >> SCAN_EXCEED_SWAP_PTE, >> SCAN_TRUNCATED, >> + SCAN_PAGE_HAS_PRIVATE, >> }; >>=20 >> #define CREATE_TRACE_POINTS >> @@ -404,7 +405,11 @@ static bool hugepage_vma_check(struct vm_area_struc= t *vma, >> (vm_flags & VM_NOHUGEPAGE) || >> test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags)) >> return false; >> - if (shmem_file(vma->vm_file)) { >> + >> + if (shmem_file(vma->vm_file) || >> + (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && >> + vma->vm_file && >> + (vm_flags & VM_DENYWRITE))) { >> if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) >> return false; >> return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, >> @@ -456,8 +461,9 @@ int khugepaged_enter_vma_merge(struct vm_area_struct= *vma, >> unsigned long hstart, hend; >>=20 >> /* >> - * khugepaged does not yet work on non-shmem files or special >> - * mappings. And file-private shmem THP is not supported. >> + * khugepaged only supports read-only files for non-shmem files. >> + * khugepaged does not yet work on special mappings. And >> + * file-private shmem THP is not supported. >> */ >> if (!hugepage_vma_check(vma, vm_flags)) >> return 0; >> @@ -1287,12 +1293,12 @@ static void retract_page_tables(struct address_s= pace *mapping, pgoff_t pgoff) >> } >>=20 >> /** >> - * collapse_file - collapse small tmpfs/shmem pages into huge one. >> + * collapse_file - collapse filemap/tmpfs/shmem pages into huge one. >> * >> * Basic scheme is simple, details are more complex: >> * - allocate and lock a new huge page; >> * - scan page cache replacing old pages with the new one >> - * + swap in pages if necessary; >> + * + swap/gup in pages if necessary; >> * + fill in gaps; >> * + keep old pages around in case rollback is required; >> * - if replacing succeeds: >> @@ -1316,7 +1322,11 @@ static void collapse_file(struct mm_struct *mm, >> LIST_HEAD(pagelist); >> XA_STATE_ORDER(xas, &mapping->i_pages, start, HPAGE_PMD_ORDER); >> int nr_none =3D 0, result =3D SCAN_SUCCEED; >> + bool is_shmem =3D shmem_file(file); >>=20 >> +#ifndef CONFIG_READ_ONLY_THP_FOR_FS >> + VM_BUG_ON(!is_shmem); >> +#endif >=20 > VM_BUG_ON(!IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && !is_shmem); Will fix.=20 >=20 >> VM_BUG_ON(start & (HPAGE_PMD_NR - 1)); >>=20 >> /* Only allocate from the target node */ >> @@ -1348,7 +1358,8 @@ static void collapse_file(struct mm_struct *mm, >> } while (1); >>=20 >> __SetPageLocked(new_page); >> - __SetPageSwapBacked(new_page); >> + if (is_shmem) >> + __SetPageSwapBacked(new_page); >> new_page->index =3D start; >> new_page->mapping =3D mapping; >>=20 >> @@ -1363,7 +1374,7 @@ static void collapse_file(struct mm_struct *mm, >> struct page *page =3D xas_next(&xas); >>=20 >> VM_BUG_ON(index !=3D xas.xa_index); >> - if (!page) { >> + if (is_shmem && !page) { >> /* >> * Stop if extent has been truncated or hole-punched, >> * and is now completely empty. >> @@ -1384,7 +1395,7 @@ static void collapse_file(struct mm_struct *mm, >> continue; >> } >>=20 >> - if (xa_is_value(page) || !PageUptodate(page)) { >> + if (is_shmem && (xa_is_value(page) || !PageUptodate(page))) { >> xas_unlock_irq(&xas); >> /* swap in or instantiate fallocated page */ >> if (shmem_getpage(mapping->host, index, &page, >> @@ -1392,6 +1403,23 @@ static void collapse_file(struct mm_struct *mm, >> result =3D SCAN_FAIL; >> goto xa_unlocked; >> } >> + } else if (!page || xa_is_value(page)) { >> + xas_unlock_irq(&xas); >> + page_cache_sync_readahead(mapping, &file->f_ra, file, >> + index, PAGE_SIZE); >> + lru_add_drain(); >=20 > Why? isolate_lru_page() is likely to fail if we don't drain the pagevecs.=20 >=20 >> + page =3D find_lock_page(mapping, index); >> + if (unlikely(page =3D=3D NULL)) { >> + result =3D SCAN_FAIL; >> + goto xa_unlocked; >> + } >> + } else if (!PageUptodate(page)) { >=20 > Maybe we should try wait_on_page_locked() here before give up? Are you referring to the "if (!PageUptodate(page))" case?=20 >=20 >> + VM_BUG_ON(is_shmem); >> + result =3D SCAN_FAIL; >> + goto xa_locked; >> + } else if (!is_shmem && PageDirty(page)) { >> + result =3D SCAN_FAIL; >> + goto xa_locked; >> } else if (trylock_page(page)) { >> get_page(page); >> xas_unlock_irq(&xas); > --=20 > Kirill A. Shutemov