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From: Christoph Hellwig <hch@infradead.org>
To: Qu Wenruo <quwenruo.btrfs@gmx.com>
Cc: Neal Gompa <ngompa13@gmail.com>, David Sterba <dsterba@suse.com>,
	Btrfs BTRFS <linux-btrfs@vger.kernel.org>
Subject: Re: [PATCH 0/6] Remove highmem allocations, kmap/kunmap
Date: Fri, 9 Jul 2021 07:46:17 +0100	[thread overview]
Message-ID: <YOfwuQPtXScmFULF@infradead.org> (raw)
In-Reply-To: <e6a4b354-879b-a767-3f21-2535e38e8571@gmx.com>

On Fri, Jul 09, 2021 at 07:53:39AM +0800, Qu Wenruo wrote:
> Sorry, I can't see the reason why it would cause performance drop or
> higher memory usage.
> 
> The point of HIGHMEM is to work on archs where system can only access
> memory below 4G reliably, any memory above 4G must be manually mapped
> into the 4G range before access.
> 
> AFAIK it's only x86 using PAE needs this, and none of the ARM SoC uses
> such feature.

Arm calls it LPAE, but otherwise it is the same.

  reply	other threads:[~2021-07-09  6:46 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-08 11:45 [PATCH 0/6] Remove highmem allocations, kmap/kunmap David Sterba
2021-07-08 11:45 ` [PATCH 1/6] btrfs: drop from __GFP_HIGHMEM all allocations David Sterba
2021-07-08 11:45 ` [PATCH 2/6] btrfs: compression: drop kmap/kunmap from lzo David Sterba
2021-07-08 11:45 ` [PATCH 3/6] btrfs: compression: drop kmap/kunmap from zlib David Sterba
2021-07-08 11:45 ` [PATCH 4/6] btrfs: compression: drop kmap/kunmap from zstd David Sterba
2021-07-08 11:45 ` [PATCH 5/6] btrfs: compression: drop kmap/kunmap from generic helpers David Sterba
2021-07-08 11:45 ` [PATCH 6/6] btrfs: check-integrity: drop kmap/kunmap for block pages David Sterba
2021-07-08 12:45 ` [PATCH 0/6] Remove highmem allocations, kmap/kunmap Neal Gompa
2021-07-08 12:49   ` David Sterba
2021-07-08 22:24     ` Neal Gompa
2021-07-08 23:53   ` Qu Wenruo
2021-07-09  6:46     ` Christoph Hellwig [this message]
2021-07-09  7:12       ` Qu Wenruo
2021-07-09 12:15         ` Neal Gompa
2021-07-10  9:50           ` Qu Wenruo
2021-07-10 11:15             ` Christoph Hellwig
2021-07-10 11:37               ` Qu Wenruo

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