Messages in this thread | | | Date | Mon, 24 Oct 2016 12:01:22 -0400 | From | Johannes Weiner <> | Subject | Re: [PATCH 3/5] lib: radix-tree: native accounting and tracking of special entries |
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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
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