From: Dave Hansen <dave.hansen@intel.com>
To: Prakash Sangappa <prakash.sangappa@oracle.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH RFC] hugetlbfs 'noautofill' mount option
Date: Tue, 2 May 2017 16:43:50 -0700 [thread overview]
Message-ID: <22557bf3-14bb-de02-7b1b-a79873c583f1@intel.com> (raw)
In-Reply-To: <03127895-3c5a-5182-82de-3baa3116749e@oracle.com>
On 05/02/2017 04:34 PM, Prakash Sangappa wrote:
> Similarly, a madvise() option also requires additional system call by every
> process mapping the file, this is considered a overhead for the database.
How long-lived are these processes? For a database, I'd assume that
this would happen a single time, or a single time per mmap() at process
startup time. Such a syscall would be doing something on the order of
taking mmap_sem, walking the VMA tree, setting a bit per VMA, and
unlocking. That's a pretty cheap one-time cost...
> If we do consider a new madvise() option, will it be acceptable
> since this will be specifically for hugetlbfs file mappings?
Ideally, it would be something that is *not* specifically for hugetlbfs.
MADV_NOAUTOFILL, for instance, could be defined to SIGSEGV whenever
memory is touched that was not populated with MADV_WILLNEED, mlock(), etc...
> If so,
> would a new flag to mmap() call itself be acceptable, which would
> define the proposed behavior?. That way no additional system calls
> need to be made.
I don't feel super strongly about it, but I guess an mmap() flag could
work too.
next prev parent reply other threads:[~2017-05-02 23:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <326e38dd-b4a8-e0ca-6ff7-af60e8045c74@oracle.com>
2017-05-01 18:00 ` [PATCH RFC] hugetlbfs 'noautofill' mount option Prakash Sangappa
2017-05-02 10:53 ` Anshuman Khandual
2017-05-02 16:07 ` Prakash Sangappa
2017-05-02 21:32 ` Dave Hansen
2017-05-02 23:34 ` Prakash Sangappa
2017-05-02 23:43 ` Dave Hansen [this message]
2017-05-03 19:02 ` Prakash Sangappa
2017-05-08 5:57 ` Prakash Sangappa
2017-05-08 15:58 ` Dave Hansen
2017-05-08 22:12 ` prakash.sangappa
2017-05-09 8:58 ` Christoph Hellwig
2017-05-09 20:59 ` Prakash Sangappa
2017-05-16 16:51 ` Prakash Sangappa
2017-06-16 13:15 ` Andrea Arcangeli
2017-06-20 23:35 ` Prakash Sangappa
2017-06-27 20:57 ` Prakash Sangappa
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