From: Dave Hansen <dave.hansen@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: Andy Lutomirski <luto@amacapital.net>,
linux-mm@kvack.org, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC 0/3] Add madvise(..., MADV_WILLWRITE)
Date: Wed, 07 Aug 2013 10:40:52 -0700 [thread overview]
Message-ID: <520286A4.1020101@intel.com> (raw)
In-Reply-To: <20130807134058.GC12843@quack.suse.cz>
On 08/07/2013 06:40 AM, Jan Kara wrote:
> One question before I look at the patches: Why don't you use fallocate()
> in your application? The functionality you require seems to be pretty
> similar to it - writing to an already allocated block is usually quick.
One problem I've seen is that it still costs you a fault per-page to get
the PTEs in to a state where you can write to the memory. MADV_WILLNEED
will do readahead to get the page cache filled, but it still leaves the
pages unmapped. Those faults get expensive when you're trying to do a
couple hundred million of them all at once.
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Hansen <dave.hansen@intel.com>
To: Jan Kara <jack@suse.cz>
Cc: Andy Lutomirski <luto@amacapital.net>,
linux-mm@kvack.org, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC 0/3] Add madvise(..., MADV_WILLWRITE)
Date: Wed, 07 Aug 2013 10:40:52 -0700 [thread overview]
Message-ID: <520286A4.1020101@intel.com> (raw)
In-Reply-To: <20130807134058.GC12843@quack.suse.cz>
On 08/07/2013 06:40 AM, Jan Kara wrote:
> One question before I look at the patches: Why don't you use fallocate()
> in your application? The functionality you require seems to be pretty
> similar to it - writing to an already allocated block is usually quick.
One problem I've seen is that it still costs you a fault per-page to get
the PTEs in to a state where you can write to the memory. MADV_WILLNEED
will do readahead to get the page cache filled, but it still leaves the
pages unmapped. Those faults get expensive when you're trying to do a
couple hundred million of them all at once.
next prev parent reply other threads:[~2013-08-07 17:40 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-05 19:43 [RFC 0/3] Add madvise(..., MADV_WILLWRITE) Andy Lutomirski
2013-08-05 19:43 ` Andy Lutomirski
2013-08-05 19:43 ` [RFC 1/3] mm: Add MADV_WILLWRITE to indicate that a range will be written to Andy Lutomirski
2013-08-05 19:43 ` Andy Lutomirski
2013-08-05 19:44 ` [RFC 2/3] fs: Add block_willwrite Andy Lutomirski
2013-08-05 19:44 ` Andy Lutomirski
2013-08-05 19:44 ` [RFC 3/3] ext4: Implement willwrite for the delalloc case Andy Lutomirski
2013-08-05 19:44 ` Andy Lutomirski
2013-08-07 13:40 ` [RFC 0/3] Add madvise(..., MADV_WILLWRITE) Jan Kara
2013-08-07 13:40 ` Jan Kara
2013-08-07 17:02 ` Andy Lutomirski
2013-08-07 17:02 ` Andy Lutomirski
2013-08-07 17:40 ` Dave Hansen [this message]
2013-08-07 17:40 ` Dave Hansen
2013-08-07 18:00 ` Andy Lutomirski
2013-08-07 18:00 ` Andy Lutomirski
2013-08-08 10:18 ` Jan Kara
2013-08-08 10:18 ` Jan Kara
2013-08-08 15:56 ` Andy Lutomirski
2013-08-08 15:56 ` Andy Lutomirski
2013-08-08 18:53 ` Jan Kara
2013-08-08 18:53 ` Jan Kara
2013-08-08 19:25 ` Andy Lutomirski
2013-08-08 19:25 ` Andy Lutomirski
2013-08-08 22:58 ` Dave Hansen
2013-08-08 22:58 ` Dave Hansen
2013-08-09 7:55 ` Jan Kara
2013-08-09 7:55 ` Jan Kara
2013-08-09 17:36 ` Andy Lutomirski
2013-08-09 17:36 ` Andy Lutomirski
2013-08-09 20:34 ` Jan Kara
2013-08-09 20:34 ` Jan Kara
2013-08-09 17:42 ` Dave Hansen
2013-08-09 17:42 ` Dave Hansen
2013-08-09 17:44 ` Andy Lutomirski
2013-08-09 17:44 ` Andy Lutomirski
2013-08-12 22:44 ` Dave Hansen
2013-08-12 22:44 ` Dave Hansen
2013-08-09 0:11 ` Andy Lutomirski
2013-08-09 0:11 ` Andy Lutomirski
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