From: Christoph Lameter <cl@linux-foundation.org>
To: Johannes Weiner <hannes@saeurebad.de>
Cc: Nick Piggin <npiggin@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-arch@vger.kernel.org
Subject: Re: [patch] mm: rewrite vmap layer
Date: Thu, 21 Aug 2008 08:13:14 -0500 [thread overview]
Message-ID: <48AD69EA.9090202@linux-foundation.org> (raw)
In-Reply-To: <87y72q3kem.fsf@skyscraper.fehenstaub.lan>
Johannes Weiner wrote:
> I have not much clue about the users but shouldn't you use vmalloc
> anyway if you don't need physically contiguous pages?
physical memory has the advantage that it does not need a page table and its
therefore more efficient to access. Plus the overhead of having to maintain a
mapping is gone. Memory is suitable for I/O without scatter gather etc etc.
> So while it would be usable then to have both vmap and vunmap work in
> atomic context, I don't really get the fallback use case..?
Classic example: A network driver wants contiguous memory for a jumbo frame.
Fallback to scatter gather is possible but not as effective.
WARNING: multiple messages have this Message-ID (diff)
From: Christoph Lameter <cl@linux-foundation.org>
To: Johannes Weiner <hannes@saeurebad.de>
Cc: Nick Piggin <npiggin@suse.de>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-arch@vger.kernel.org
Subject: Re: [patch] mm: rewrite vmap layer
Date: Thu, 21 Aug 2008 08:13:14 -0500 [thread overview]
Message-ID: <48AD69EA.9090202@linux-foundation.org> (raw)
In-Reply-To: <87y72q3kem.fsf@skyscraper.fehenstaub.lan>
Johannes Weiner wrote:
> I have not much clue about the users but shouldn't you use vmalloc
> anyway if you don't need physically contiguous pages?
physical memory has the advantage that it does not need a page table and its
therefore more efficient to access. Plus the overhead of having to maintain a
mapping is gone. Memory is suitable for I/O without scatter gather etc etc.
> So while it would be usable then to have both vmap and vunmap work in
> atomic context, I don't really get the fallback use case..?
Classic example: A network driver wants contiguous memory for a jumbo frame.
Fallback to scatter gather is possible but not as effective.
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next prev parent reply other threads:[~2008-08-21 13:14 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-18 13:32 [patch] mm: rewrite vmap layer Nick Piggin
2008-08-18 13:32 ` Nick Piggin
2008-08-19 0:24 ` Andrew Morton
2008-08-19 0:24 ` Andrew Morton
2008-08-19 7:37 ` Russell King
2008-08-19 7:37 ` Russell King
2008-08-19 10:39 ` Nick Piggin
2008-08-19 10:39 ` Nick Piggin
2008-08-20 3:32 ` Kyle McMartin
2008-08-20 3:32 ` Kyle McMartin
2008-08-19 10:02 ` Nick Piggin
2008-08-19 10:02 ` Nick Piggin
2008-08-19 14:42 ` Christoph Lameter
2008-08-19 14:42 ` Christoph Lameter
2008-08-20 9:02 ` Nick Piggin
2008-08-20 9:02 ` Nick Piggin
2008-08-20 14:03 ` Christoph Lameter
2008-08-20 14:03 ` Christoph Lameter
2008-08-20 16:22 ` Nick Piggin
2008-08-20 16:22 ` Nick Piggin
2008-08-20 16:50 ` Christoph Lameter
2008-08-20 16:50 ` Christoph Lameter
2008-08-20 16:59 ` Nick Piggin
2008-08-20 16:59 ` Nick Piggin
2008-08-20 17:05 ` Christoph Lameter
2008-08-20 17:05 ` Christoph Lameter
2008-08-20 17:48 ` Nick Piggin
2008-08-20 17:48 ` Nick Piggin
2008-08-21 7:19 ` Johannes Weiner
2008-08-21 7:19 ` Johannes Weiner
2008-08-21 13:13 ` Christoph Lameter [this message]
2008-08-21 13:13 ` Christoph Lameter
2008-09-05 3:06 ` Andrew Morton
2008-09-05 3:06 ` Andrew Morton
2008-09-07 12:06 ` Nick Piggin
2008-09-07 12:06 ` Nick Piggin
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