From: Michal Hocko <mhocko@kernel.org> To: linux-api@vger.kernel.org Cc: Andrew Morton <akpm@linux-foundation.org>, Alexey Dobriyan <adobriyan@gmail.com>, <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Dan Williams <dan.j.williams@intel.com>, David Rientjes <rientjes@google.com>, Jan Kara <jack@suse.cz>, Michal Hocko <mhocko@suse.com> Subject: [RFC PATCH 0/3] THP eligibility reporting via proc Date: Tue, 20 Nov 2018 11:35:12 +0100 [thread overview] Message-ID: <20181120103515.25280-1-mhocko@kernel.org> (raw) Hi, this series of three patches aims at making THP eligibility reporting much more robust and long term sustainable. The trigger for the change is a regression report [1] and the long follow up discussion. In short the specific application didn't have good API to query whether a particular mapping can be backed by THP so it has used VMA flags to workaround that. These flags represent a deep internal state of VMAs and as such they should be used by userspace with a great deal of caution. A similar has happened for [2] when users complained that VM_MIXEDMAP is no longer set on DAX mappings. Again a lack of a proper API led to an abuse. The first patch in the series tries to emphasise that that the semantic of flags might change and any application consuming those should be really careful. The remaining two patches provide a more suitable interface to address [1] and provide a consistent API to query the THP status both for each VMA and process wide as well. [1] http://lkml.kernel.org/r/http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com [2] http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@kernel.org> To: linux-api@vger.kernel.org Cc: Andrew Morton <akpm@linux-foundation.org>, Alexey Dobriyan <adobriyan@gmail.com>, linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>, Dan Williams <dan.j.williams@intel.com>, David Rientjes <rientjes@google.com>, Jan Kara <jack@suse.cz>, Michal Hocko <mhocko@suse.com> Subject: [RFC PATCH 0/3] THP eligibility reporting via proc Date: Tue, 20 Nov 2018 11:35:12 +0100 [thread overview] Message-ID: <20181120103515.25280-1-mhocko@kernel.org> (raw) Hi, this series of three patches aims at making THP eligibility reporting much more robust and long term sustainable. The trigger for the change is a regression report [1] and the long follow up discussion. In short the specific application didn't have good API to query whether a particular mapping can be backed by THP so it has used VMA flags to workaround that. These flags represent a deep internal state of VMAs and as such they should be used by userspace with a great deal of caution. A similar has happened for [2] when users complained that VM_MIXEDMAP is no longer set on DAX mappings. Again a lack of a proper API led to an abuse. The first patch in the series tries to emphasise that that the semantic of flags might change and any application consuming those should be really careful. The remaining two patches provide a more suitable interface to address [1] and provide a consistent API to query the THP status both for each VMA and process wide as well. [1] http://lkml.kernel.org/r/http://lkml.kernel.org/r/alpine.DEB.2.21.1809241054050.224429@chino.kir.corp.google.com [2] http://lkml.kernel.org/r/20181002100531.GC4135@quack2.suse.cz
next reply other threads:[~2018-11-20 10:35 UTC|newest] Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-11-20 10:35 Michal Hocko [this message] 2018-11-20 10:35 ` [RFC PATCH 0/3] THP eligibility reporting via proc Michal Hocko 2018-11-20 10:35 ` [RFC PATCH 1/3] mm, proc: be more verbose about unstable VMA flags in /proc/<pid>/smaps Michal Hocko 2018-11-20 10:35 ` Michal Hocko 2018-11-20 10:51 ` Jan Kara 2018-11-20 11:41 ` Michal Hocko 2018-11-21 0:01 ` David Rientjes 2018-11-21 6:56 ` Michal Hocko 2018-11-20 18:32 ` Dan Williams 2018-11-21 7:05 ` Michal Hocko 2018-11-21 18:01 ` Mike Rapoport 2018-11-21 17:54 ` Mike Rapoport 2018-11-21 17:58 ` Michal Hocko 2018-11-23 13:47 ` Vlastimil Babka 2018-11-20 10:35 ` [RFC PATCH 2/3] mm, thp, proc: report THP eligibility for each vma Michal Hocko 2018-11-20 10:35 ` Michal Hocko 2018-11-20 11:42 ` Michal Hocko 2018-11-23 15:07 ` Vlastimil Babka 2018-11-23 15:21 ` Michal Hocko 2018-11-23 15:24 ` Vlastimil Babka 2018-11-20 10:35 ` [RFC PATCH 3/3] mm, proc: report PR_SET_THP_DISABLE in proc Michal Hocko 2018-11-20 10:35 ` Michal Hocko 2018-11-20 11:42 ` Michal Hocko 2018-11-23 15:49 ` Vlastimil Babka 2018-11-27 0:33 ` William Kucharski 2018-11-27 13:17 ` Michal Hocko 2018-11-27 14:50 ` William Kucharski 2018-11-27 16:25 ` Michal Hocko 2018-11-27 16:50 ` Vlastimil Babka 2018-11-27 17:06 ` William Kucharski 2018-12-07 10:55 ` [RFC PATCH 0/3] THP eligibility reporting via proc Michal Hocko
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