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From: Andy Lutomirski <luto@kernel.org>
To: Joerg Roedel <joro@8bytes.org>
Cc: X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
	 Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	 Peter Zijlstra <peterz@infradead.org>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Arnd Bergmann <arnd@arndb.de>,
	 Andrew Morton <akpm@linux-foundation.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	 Vlastimil Babka <vbabka@suse.cz>,
	Michal Hocko <mhocko@kernel.org>, Joerg Roedel <jroedel@suse.de>,
	 LKML <linux-kernel@vger.kernel.org>,
	Linux ACPI <linux-acpi@vger.kernel.org>,
	 linux-arch <linux-arch@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>
Subject: Re: [RFC PATCH 0/7] mm: Get rid of vmalloc_sync_(un)mappings()
Date: Fri, 8 May 2020 14:33:19 -0700	[thread overview]
Message-ID: <CALCETrX0ubjc0Gf4hCY9RWH6cVEKF1hv3RzqToKMt9_bEXXBvw@mail.gmail.com> (raw)
In-Reply-To: <20200508144043.13893-1-joro@8bytes.org>

On Fri, May 8, 2020 at 7:40 AM Joerg Roedel <joro@8bytes.org> wrote:
>
> Hi,
>
> after the recent issue with vmalloc and tracing code[1] on x86 and a
> long history of previous issues related to the vmalloc_sync_mappings()
> interface, I thought the time has come to remove it. Please
> see [2], [3], and [4] for some other issues in the past.
>
> The patches are based on v5.7-rc4 and add tracking of page-table
> directory changes to the vmalloc and ioremap code. Depending on which
> page-table levels changes have been made, a new per-arch function is
> called: arch_sync_kernel_mappings().
>
> On x86-64 with 4-level paging, this function will not be called more
> than 64 times in a systems runtime (because vmalloc-space takes 64 PGD
> entries which are only populated, but never cleared).

What's the maximum on other system types?  It might make more sense to
take the memory hit and pre-populate all the tables at boot so we
never have to sync them.


  parent reply	other threads:[~2020-05-08 21:33 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-08 14:40 [RFC PATCH 0/7] mm: Get rid of vmalloc_sync_(un)mappings() Joerg Roedel
2020-05-08 14:40 ` [RFC PATCH 1/7] mm: Add functions to track page directory modifications Joerg Roedel
2020-05-08 14:40 ` [RFC PATCH 2/7] mm/vmalloc: Track which page-table levels were modified Joerg Roedel
2020-05-08 19:10   ` Peter Zijlstra
2020-05-08 21:23     ` Joerg Roedel
2020-05-08 14:40 ` [RFC PATCH 3/7] mm/ioremap: " Joerg Roedel
2020-05-08 14:40 ` [RFC PATCH 4/7] x86/mm/64: Implement arch_sync_kernel_mappings() Joerg Roedel
2020-05-08 14:40 ` [RFC PATCH 5/7] x86/mm/32: " Joerg Roedel
2020-05-08 14:40 ` [RFC PATCH 6/7] mm: Remove vmalloc_sync_(un)mappings() Joerg Roedel
2020-05-08 18:58   ` Steven Rostedt
2020-05-08 21:24     ` Joerg Roedel
2020-05-08 14:40 ` [RFC PATCH 7/7] x86/mm: Remove vmalloc faulting Joerg Roedel
2020-05-08 19:20 ` [RFC PATCH 0/7] mm: Get rid of vmalloc_sync_(un)mappings() Peter Zijlstra
2020-05-08 21:34   ` Joerg Roedel
2020-05-09  9:25     ` Peter Zijlstra
2020-05-09 17:54       ` Joerg Roedel
2020-05-10  1:11       ` Matthew Wilcox
2020-05-11  7:31         ` Peter Zijlstra
2020-05-11 15:52           ` Matthew Wilcox
2020-05-11 16:08             ` Matthew Wilcox
2020-05-11 17:02             ` Peter Zijlstra
2020-05-08 21:33 ` Andy Lutomirski [this message]
2020-05-08 21:36   ` Joerg Roedel
2020-05-08 23:49     ` Andy Lutomirski
2020-05-09 17:52       ` Joerg Roedel
2020-05-09 19:05         ` Andy Lutomirski
2020-05-09 21:57           ` Joerg Roedel
2020-05-10  5:05             ` Andy Lutomirski
2020-05-10  8:15               ` Joerg Roedel
2020-05-11  7:42           ` Peter Zijlstra
2020-05-11 15:36             ` Andy Lutomirski
2020-05-11 17:06               ` Peter Zijlstra
2020-05-11 19:14               ` Joerg Roedel
2020-05-11 19:36                 ` Andy Lutomirski
2020-05-12 15:02                   ` Joerg Roedel
2020-05-12 15:13                     ` Steven Rostedt
2020-05-11 20:50                 ` Steven Rostedt

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