From: Matthew Wilcox <willy@infradead.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>,
Christoph Lameter <cl@linux.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@lge.com,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: copy_page() on a kmalloc-ed page with DEBUG_SLAB enabled (was "zram: do not use copy_page with non-page alinged address")
Date: Wed, 19 Apr 2017 04:51:25 -0700 [thread overview]
Message-ID: <20170419115125.GA27790@bombadil.infradead.org> (raw)
In-Reply-To: <20170419060237.GA1636@bbox>
On Wed, Apr 19, 2017 at 03:02:37PM +0900, Minchan Kim wrote:
> On Tue, Apr 18, 2017 at 09:33:07AM +0200, Michal Hocko wrote:
> > I do not follow. Why would you need kmap for something that is already
> > in the kernel space?
>
> Because it can work with highmem pages.
That's copy_user_highpage(). If you want to define a new arch API
copy_highpage(), feel free to make a case for it ...
> > > Another approach is the API does normal thing for non-aligned prefix and
> > > tail space and fast thing for aligned space.
> > > Otherwise, it would be happy if the API has WARN_ON non-page SIZE aligned
> > > address.
Why not just use memcpy()? Is copy_page() significantly faster than
memcpy() for a PAGE_SIZE amount of data?
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next prev parent reply other threads:[~2017-04-19 11:51 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-17 1:48 copy_page() on a kmalloc-ed page with DEBUG_SLAB enabled (was "zram: do not use copy_page with non-page alinged address") Sergey Senozhatsky
2017-04-17 15:20 ` Christoph Lameter
2017-04-18 0:03 ` Minchan Kim
2017-04-18 7:33 ` Michal Hocko
2017-04-18 10:56 ` Sergey Senozhatsky
2017-04-18 11:06 ` Michal Hocko
2017-04-19 6:11 ` Sergey Senozhatsky
2017-04-19 6:02 ` Minchan Kim
2017-04-19 11:51 ` Matthew Wilcox [this message]
2017-04-20 1:45 ` Sergey Senozhatsky
2017-04-20 6:50 ` Minchan Kim
2017-04-18 10:42 ` Sergey Senozhatsky
2017-04-18 13:28 ` Christoph Lameter
2017-04-18 13:13 ` Matthew Wilcox
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