From: Vlastimil Babka <vbabka@suse.cz> To: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Dave Hansen <dave.hansen@intel.com>, Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>, Christoph Lameter <cl@gentwo.org>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, Steve Capper <steve.capper@linaro.org>, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>, Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>, Jerome Marchand <jmarchan@redhat.com>, Sasha Levin <sasha.levin@oracle.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv5 19/28] mm: store mapcount for compound page separately Date: Tue, 19 May 2015 11:01:39 +0200 [thread overview] Message-ID: <555AFBF3.1010601@suse.cz> (raw) In-Reply-To: <20150519035515.GA5795@node.dhcp.inet.fi> On 05/19/2015 05:55 AM, Kirill A. Shutemov wrote: >> >>> + if (compound_mapcount(page)) >>> + ret += compound_mapcount(page) - 1; >> >> This looks like it could uselessly duplicate-inline the code for >> compound_mapcount(). It has atomics and smp_rmb() so I'm not sure if the >> compiler can just "squash it". > > Good point. I'll rework this. Hm BTW I think same duplication of compound_head() happens in lock_page(), where it's done by trylock_page() and then __lock_page(), which is also in different compilation unit to make things worse. I can imagine it's solvable by introducing variants of __lock_page* that expect to be already given a head page... if it's worth the trouble. >> >> On the other hand, a simple atomic read that was page_mapcount() has turned >> into multiple atomic reads and flag checks. What about the stability of the >> whole result? Are all callers ok? (maybe a later page deals with it). > > Urghh.. I'll look into this. >
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From: Vlastimil Babka <vbabka@suse.cz> To: "Kirill A. Shutemov" <kirill@shutemov.name> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Andrea Arcangeli <aarcange@redhat.com>, Hugh Dickins <hughd@google.com>, Dave Hansen <dave.hansen@intel.com>, Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>, Christoph Lameter <cl@gentwo.org>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, Steve Capper <steve.capper@linaro.org>, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>, Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>, Jerome Marchand <jmarchan@redhat.com>, Sasha Levin <sasha.levin@oracle.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv5 19/28] mm: store mapcount for compound page separately Date: Tue, 19 May 2015 11:01:39 +0200 [thread overview] Message-ID: <555AFBF3.1010601@suse.cz> (raw) In-Reply-To: <20150519035515.GA5795@node.dhcp.inet.fi> On 05/19/2015 05:55 AM, Kirill A. Shutemov wrote: >> >>> + if (compound_mapcount(page)) >>> + ret += compound_mapcount(page) - 1; >> >> This looks like it could uselessly duplicate-inline the code for >> compound_mapcount(). It has atomics and smp_rmb() so I'm not sure if the >> compiler can just "squash it". > > Good point. I'll rework this. Hm BTW I think same duplication of compound_head() happens in lock_page(), where it's done by trylock_page() and then __lock_page(), which is also in different compilation unit to make things worse. I can imagine it's solvable by introducing variants of __lock_page* that expect to be already given a head page... if it's worth the trouble. >> >> On the other hand, a simple atomic read that was page_mapcount() has turned >> into multiple atomic reads and flag checks. What about the stability of the >> whole result? Are all callers ok? (maybe a later page deals with it). > > Urghh.. I'll look into this. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-05-19 9:01 UTC|newest] Thread overview: 189+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-04-23 21:03 [PATCHv5 00/28] THP refcounting redesign Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 01/28] mm, proc: adjust PSS calculation Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 15:49 ` Jerome Marchand 2015-05-14 14:12 ` Vlastimil Babka 2015-05-14 14:12 ` Vlastimil Babka 2015-05-15 10:56 ` Kirill A. Shutemov 2015-05-15 10:56 ` Kirill A. Shutemov 2015-05-15 11:33 ` Vlastimil Babka 2015-05-15 11:33 ` Vlastimil Babka 2015-05-15 11:43 ` Kirill A. Shutemov 2015-05-15 11:43 ` Kirill A. Shutemov 2015-05-15 12:37 ` Vlastimil Babka 2015-05-15 12:37 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 02/28] rmap: add argument to charge compound page Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 15:53 ` Jerome Marchand 2015-04-30 11:52 ` Kirill A. Shutemov 2015-04-30 11:52 ` Kirill A. Shutemov 2015-05-14 16:07 ` Vlastimil Babka 2015-05-14 16:07 ` Vlastimil Babka 2015-05-15 11:14 ` Kirill A. Shutemov 2015-05-15 11:14 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 03/28] memcg: adjust to support new THP refcounting Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-15 7:44 ` Vlastimil Babka 2015-05-15 7:44 ` Vlastimil Babka 2015-05-15 11:18 ` Kirill A. Shutemov 2015-05-15 11:18 ` Kirill A. Shutemov 2015-05-15 14:57 ` Dave Hansen 2015-05-15 14:57 ` Dave Hansen 2015-05-16 23:17 ` Kirill A. Shutemov 2015-05-16 23:17 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 04/28] mm, thp: adjust conditions when we can reuse the page on WP fault Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 15:54 ` Jerome Marchand 2015-05-15 9:15 ` Vlastimil Babka 2015-05-15 9:15 ` Vlastimil Babka 2015-05-15 11:21 ` Kirill A. Shutemov 2015-05-15 11:21 ` Kirill A. Shutemov 2015-05-15 11:35 ` Vlastimil Babka 2015-05-15 11:35 ` Vlastimil Babka 2015-05-15 13:29 ` Kirill A. Shutemov 2015-05-15 13:29 ` Kirill A. Shutemov 2015-05-19 13:00 ` Vlastimil Babka 2015-05-19 13:00 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 05/28] mm: adjust FOLL_SPLIT for new refcounting Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-15 11:05 ` Vlastimil Babka 2015-05-15 11:05 ` Vlastimil Babka 2015-05-15 11:36 ` Kirill A. Shutemov 2015-05-15 11:36 ` Kirill A. Shutemov 2015-05-15 12:01 ` Vlastimil Babka 2015-05-15 12:01 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 06/28] mm: handle PTE-mapped tail pages in gerneric fast gup implementaiton Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 15:56 ` Jerome Marchand 2015-05-15 12:46 ` Vlastimil Babka 2015-05-15 12:46 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 07/28] thp, mlock: do not allow huge pages in mlocked area Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 15:58 ` Jerome Marchand 2015-05-15 12:56 ` Vlastimil Babka 2015-05-15 12:56 ` Vlastimil Babka 2015-05-15 13:41 ` Kirill A. Shutemov 2015-05-15 13:41 ` Kirill A. Shutemov 2015-05-19 14:37 ` Vlastimil Babka 2015-05-19 14:37 ` Vlastimil Babka 2015-05-20 12:10 ` Kirill A. Shutemov 2015-05-20 12:10 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 08/28] khugepaged: ignore pmd tables with THP mapped with ptes Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 15:59 ` Jerome Marchand 2015-05-15 12:59 ` Vlastimil Babka 2015-05-15 12:59 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 09/28] thp: rename split_huge_page_pmd() to split_huge_pmd() Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 16:00 ` Jerome Marchand 2015-05-15 13:08 ` Vlastimil Babka 2015-05-15 13:08 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 10/28] mm, vmstats: new THP splitting event Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 16:02 ` Jerome Marchand 2015-05-15 13:10 ` Vlastimil Babka 2015-05-15 13:10 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 11/28] mm: temporally mark THP broken Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 12/28] thp: drop all split_huge_page()-related code Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 13/28] mm: drop tail page refcounting Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-18 9:48 ` Vlastimil Babka 2015-05-18 9:48 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 14/28] futex, thp: remove special case for THP in get_futex_key Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-18 11:49 ` Vlastimil Babka 2015-05-18 11:49 ` Vlastimil Babka 2015-05-18 12:13 ` Kirill A. Shutemov 2015-05-18 12:13 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 15/28] ksm: prepare to new THP semantics Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-18 12:41 ` Vlastimil Babka 2015-05-18 12:41 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 16/28] mm, thp: remove compound_lock Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 16:11 ` Jerome Marchand 2015-04-30 11:58 ` Kirill A. Shutemov 2015-04-30 11:58 ` Kirill A. Shutemov 2015-05-18 12:57 ` Vlastimil Babka 2015-05-18 12:57 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 17/28] mm, thp: remove infrastructure for handling splitting PMDs Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 16:14 ` Jerome Marchand 2015-04-30 12:03 ` Kirill A. Shutemov 2015-04-30 12:03 ` Kirill A. Shutemov 2015-05-18 13:40 ` Vlastimil Babka 2015-05-18 13:40 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 18/28] x86, " Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 9:13 ` Aneesh Kumar K.V 2015-04-29 9:13 ` Aneesh Kumar K.V 2015-04-23 21:03 ` [PATCHv5 19/28] mm: store mapcount for compound page separately Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-18 14:32 ` Vlastimil Babka 2015-05-18 14:32 ` Vlastimil Babka 2015-05-19 3:55 ` Kirill A. Shutemov 2015-05-19 3:55 ` Kirill A. Shutemov 2015-05-19 9:01 ` Vlastimil Babka [this message] 2015-05-19 9:01 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 20/28] mm: differentiate page_mapped() from page_mapcount() for compound pages Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-29 16:20 ` Jerome Marchand 2015-04-30 12:06 ` Kirill A. Shutemov 2015-04-30 12:06 ` Kirill A. Shutemov 2015-05-18 15:35 ` Vlastimil Babka 2015-05-18 15:35 ` Vlastimil Babka 2015-05-19 4:00 ` Kirill A. Shutemov 2015-05-19 4:00 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 21/28] mm, numa: skip PTE-mapped THP on numa fault Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 22/28] thp: implement split_huge_pmd() Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-19 8:25 ` Vlastimil Babka 2015-05-19 8:25 ` Vlastimil Babka 2015-05-20 14:38 ` Kirill A. Shutemov 2015-05-20 14:38 ` Kirill A. Shutemov 2015-04-23 21:03 ` [PATCHv5 23/28] thp: add option to setup migration entiries during PMD split Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-19 13:55 ` Vlastimil Babka 2015-05-19 13:55 ` Vlastimil Babka 2015-04-23 21:03 ` [PATCHv5 24/28] thp, mm: split_huge_page(): caller need to lock page Kirill A. Shutemov 2015-04-23 21:03 ` Kirill A. Shutemov 2015-05-19 13:55 ` Vlastimil Babka 2015-05-19 13:55 ` Vlastimil Babka 2015-04-23 21:04 ` [PATCHv5 25/28] thp: reintroduce split_huge_page() Kirill A. Shutemov 2015-04-23 21:04 ` Kirill A. Shutemov 2015-05-19 12:43 ` Vlastimil Babka 2015-05-19 12:43 ` Vlastimil Babka 2015-04-23 21:04 ` [PATCHv5 26/28] thp: introduce deferred_split_huge_page() Kirill A. Shutemov 2015-04-23 21:04 ` Kirill A. Shutemov 2015-05-19 13:54 ` Vlastimil Babka 2015-05-19 13:54 ` Vlastimil Babka 2015-04-23 21:04 ` [PATCHv5 27/28] mm: re-enable THP Kirill A. Shutemov 2015-04-23 21:04 ` Kirill A. Shutemov 2015-04-23 21:04 ` [PATCHv5 28/28] thp: update documentation Kirill A. Shutemov 2015-04-23 21:04 ` Kirill A. Shutemov 2015-04-27 23:03 ` [PATCHv5 00/28] THP refcounting redesign Andrew Morton 2015-04-27 23:03 ` Andrew Morton 2015-04-27 23:33 ` Kirill A. Shutemov 2015-04-27 23:33 ` Kirill A. Shutemov 2015-04-30 8:25 ` [RFC PATCH 0/3] Remove _PAGE_SPLITTING from ppc64 Aneesh Kumar K.V 2015-04-30 8:25 ` Aneesh Kumar K.V 2015-04-30 8:25 ` [RFC PATCH 1/3] mm/thp: Use pmdp_splitting_flush_notify to clear pmd on splitting Aneesh Kumar K.V 2015-04-30 8:25 ` Aneesh Kumar K.V 2015-04-30 13:30 ` Kirill A. Shutemov 2015-04-30 13:30 ` Kirill A. Shutemov 2015-04-30 15:59 ` Aneesh Kumar K.V 2015-04-30 15:59 ` Aneesh Kumar K.V 2015-04-30 16:47 ` Aneesh Kumar K.V 2015-04-30 16:47 ` Aneesh Kumar K.V 2015-04-30 8:25 ` [RFC PATCH 2/3] powerpc/thp: Remove _PAGE_SPLITTING and related code Aneesh Kumar K.V 2015-04-30 8:25 ` Aneesh Kumar K.V 2015-04-30 8:25 ` [RFC PATCH 3/3] mm/thp: Add new function to clear pmd on collapse Aneesh Kumar K.V 2015-04-30 8:25 ` Aneesh Kumar K.V 2015-05-15 8:55 ` [PATCHv5 00/28] THP refcounting redesign Vlastimil Babka 2015-05-15 8:55 ` Vlastimil Babka 2015-05-15 13:31 ` Kirill A. Shutemov 2015-05-15 13:31 ` Kirill A. Shutemov
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