On 04/23/2014 04:02 AM, Tejun Heo wrote: > On Tue, Apr 22, 2014 at 06:16:20PM +0800, Lai Jiangshan wrote: >> There are two stages of ida allocation/free, idr_layers and ida_bitmap. >> They add unneeded foot print and memory waste. >> >> When a single ID is first allocated from an ida, this ida requires >> two big chunks of memory. One idr_layer and one ida_bitmap. >> >> To reduce the foot print and memory, we reduce the ida_bitmap >> to a single "unsigned long" and place it in its own idr-slot >> and avoid to allocate the ida_bitmap. >> >> It also means ida bitmap is located on its coresponding idr-slot >> which size is the same as "unsigned long". >> Each ida bitmap(idr-slot) contains BITS_PER_LONG ida-slots. >> >> The struct ida_bitmap is not needed any more, we use "unsigned long" >> directly and remove all the code of alloc/free struct ida_bitmap. > > Are you calling 128 byte a "big chunk of memory" while trading off > tree depth for it? No, this level of space optimizaiton is completely > uncalled for.
I reduce the depth, you forgot that struct ida_bitmap is an additional depth which is removed in the patch. > > Nacked-by: Tejun Heo <t...@kernel.org> > > Thanks. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/