On Thu, 8 Dec 2016 02:22:55 +0100 Rasmus Villemoes linux@rasmusvillemoes.dk wrote:
TL;DR: these patches save 250 KB of memory, with more low-hanging fruit ready to pick.
While browsing through the lib/idr.c code, I noticed that the code at the end of ida_get_new_above() probably doesn't work as intended: Most users of ida use it via ida_simple_get(), and that starts by unconditionally calling ida_pre_get(), ensuring that ida->idr has 8==MAX_IDR_FREE idr_layers in its free list id_free. In the common case, none (or at most one) of these get used during ida_get_new_above(), and we only free one, leaving at least 6 (usually 7) idr_layers in the free list.
Please be aware of
http://ozlabs.org/~akpm/mmots/broken-out/reimplement-idr-and-ida-using-the-r... http://lkml.kernel.org/r/1480369871-5271-68-git-send-email-mawilcox@linuxonh...
I expect we'll be merging patches 1-32 of that series into 4.10-rc1 and the above patch (#33) into 4.11-rc1.