From: Johannes Weiner <hannes@cmpxchg.org>
To: Dave Chinner <david@fromorbit.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Jan Kara <jack@suse.cz>, Dave Jones <davej@codemonkey.org.uk>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
kernel-team@fb.com
Subject: Re: [PATCH 3/5] lib: radix-tree: native accounting and tracking of special entries
Date: Mon, 24 Oct 2016 12:01:22 -0400 [thread overview]
Message-ID: <20161024160122.GA2125@cmpxchg.org> (raw)
In-Reply-To: <20161020223308.GN23194@dastard>
Hi Dave,
On Fri, Oct 21, 2016 at 09:33:08AM +1100, Dave Chinner wrote:
> On Wed, Oct 19, 2016 at 01:24:26PM -0400, Johannes Weiner wrote:
> > With this in place, the next patch can restore refault detection in
> > single-page files. It will also move the shadow count from the upper
> > bits of count to the new special counter, and then shrink count to a
> > char as well; the growth of struct radix_tree_node is temporary.
[...]
> > @@ -90,9 +91,10 @@ enum radix_tree_tags {
> > #define RADIX_TREE_COUNT_MASK ((1UL << RADIX_TREE_COUNT_SHIFT) - 1)
> >
> > struct radix_tree_node {
> > - unsigned char shift; /* Bits remaining in each slot */
> > - unsigned char offset; /* Slot offset in parent */
> > - unsigned int count;
> > + unsigned char shift; /* Bits remaining in each slot */
> > + unsigned char offset; /* Slot offset in parent */
> > + unsigned int count; /* Total entry count */
> > + unsigned char special; /* Special entry count */
>
> How about putting the new char field into the implicit hole between
> offset and count? pahole is your friend here:
>
> struct radix_tree_node {
> unsigned char shift; /* 0 1 */
> unsigned char offset; /* 1 1 */
>
> /* XXX 2 bytes hole, try to pack */
>
> unsigned int count; /* 4 4 */
> .....
The next patch turns `count' into an unsigned char again, so the hole
is only temporary.
Thanks
next prev parent reply other threads:[~2016-10-24 16:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-19 17:24 [PATCH 0/5] mm: workingset: radix tree subtleties & single-page file refaults Johannes Weiner
2016-10-19 17:24 ` [PATCH 1/5] lib: radix-tree: provide node-granular interface for radix tree tags Johannes Weiner
2016-10-19 17:24 ` [PATCH 2/5] lib: radix-tree: internal tags Johannes Weiner
2016-10-19 17:24 ` [PATCH 3/5] lib: radix-tree: native accounting and tracking of special entries Johannes Weiner
2016-10-20 22:33 ` Dave Chinner
2016-10-24 16:01 ` Johannes Weiner [this message]
2016-10-19 17:24 ` [PATCH 4/5] mm: workingset: restore single-page file refault tracking Johannes Weiner
2016-10-19 17:24 ` [PATCH 5/5] mm: workingset: turn shadow node shrinker bugs into warnings Johannes Weiner
2016-10-19 18:16 ` [PATCH 0/5] mm: workingset: radix tree subtleties & single-page file refaults Linus Torvalds
2016-10-24 18:47 ` Johannes Weiner
2016-10-26 9:21 ` Jan Kara
2016-10-26 18:15 ` Johannes Weiner
2016-10-27 8:48 ` Jan Kara
2016-10-26 18:18 ` Linus Torvalds
2016-10-26 18:29 ` Johannes Weiner
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