On Tue, May 07, 2019 at 10:01:47AM -0700, Roman Gushchin wrote: > In most cases percpu reference counters are not switched to the > percpu mode after they reach the atomic mode. Some obvious exceptions > are reference counters which are initialized into the atomic > mode (using PERCPU_REF_INIT_ATOMIC and PERCPU_REF_INIT_DEAD flags), > and there are few other exceptions. > > But in most cases there is no way back, and once the reference counter > is switched to the atomic mode, there is no reason to wait for > percpu_ref_exit() to release the percpu memory. Of course, the size > of a single counter is not so big, but because it can pin the whole > percpu block in memory, the memory footprint can be noticeable > (e.g. on my 32 CPUs machine a percpu block is 8Mb large). > > To make releasing of the percpu memory as early as possible, let's > introduce the PERCPU_REF_ALLOW_REINIT flag with the following semantics: > it has to be set in order to switch a percpu reference counter to the > percpu mode after the initialization. PERCPU_REF_INIT_ATOMIC and > PERCPU_REF_INIT_DEAD flags will implicitly assume PERCPU_REF_ALLOW_REINIT. > > This patch doesn't introduce any functional change to avoid any > regressions. It will be done later in the patchset after adjusting > all call sites, which are reviving percpu counters. > > Signed-off-by: Roman Gushchin <g...@fb.com>
For all patches in the series: Acked-by: Tejun Heo <t...@kenrel.org> Thanks. -- tejun
