Hello, On Fri, Dec 09, 2016 at 02:01:40PM -0800, Andrew Morton wrote: > On Thu, 8 Dec 2016 02:22:55 +0100 Rasmus Villemoes > <li...@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-radix-tree.patch > http://lkml.kernel.org/r/1480369871-5271-68-git-send-email-mawil...@linuxonhyperv.com > > 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.
Ah, yeah, great to see the silly implementation being replaced the radix tree. ida_pre_get() looks suspicious tho. idr_preload() immedicately being followed by idr_preload_end() probably is broken. Maybe what we need is moving ida to idr like preload interface and then convert it to radix based interface? ida currently assumes per-ida preloading. Thanks. -- tejun
