Messages in this thread | | | Date | Fri, 4 Sep 2009 14:11:57 +0900 | From | Daisuke Nishimura <> | Subject | Re: [mmotm][experimental][PATCH] coalescing charge |
| |
A few more comments.
On Fri, 4 Sep 2009 13:18:35 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > On Thu, 3 Sep 2009 14:17:27 +0900 > Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote: > > > = > > > This is a code for batched charging using percpu cache. > > > At charge, memcg charges 64pages and remember it in percpu cache. > > > Because it's cache, drain/flushed if necessary. > > > > > > This version uses public percpu area , not per-memcg percpu area. > > > 2 benefits of public percpu area. > > > 1. Sum of stocked charge in the system is limited to # of cpus > > > not to the number of memcg. This shows better synchonization. > > > 2. drain code for flush/cpuhotplug is very easy (and quick) > > > > > > The most important point of this patch is that we never touch res_counter > > > in fast path. The res_counter is system-wide shared counter which is modified > > > very frequently. We shouldn't touch it as far as we can for avoid false sharing. > > > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > It looks basically good. I'll do some tests with all patches applied. > > > thanks. > it seems that these patches make rmdir stall again... This batched charge patch seems not to be the (only) suspect, though.
> > > @@ -1288,23 +1364,25 @@ static int __mem_cgroup_try_charge(struc > > > return 0; > > > > > > VM_BUG_ON(css_is_removed(&mem->css)); > > > + if (mem_cgroup_is_root(mem)) > > > + goto done; > > > + if (consume_stock(mem)) > > > + goto charged; > > > IMHO, it would be better to check consume_stock() every time in the while loop below, because someone might have already refilled the stock while the current context sleeps in reclaiming memory.
> > > while (1) { > > > int ret = 0; > > > unsigned long flags = 0; > > > > > > - if (mem_cgroup_is_root(mem)) > > > - goto done; > > > - ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res); > > > + ret = res_counter_charge(&mem->res, CHARGE_SIZE, &fail_res); > > > if (likely(!ret)) { > > > if (!do_swap_account) > > > break; > > > - ret = res_counter_charge(&mem->memsw, PAGE_SIZE, > > > + ret = res_counter_charge(&mem->memsw, CHARGE_SIZE, > > > &fail_res); > > > if (likely(!ret)) > > > break; > > > /* mem+swap counter fails */ > > > - res_counter_uncharge(&mem->res, PAGE_SIZE); > > > + res_counter_uncharge(&mem->res, CHARGE_SIZE); > > > flags |= MEM_CGROUP_RECLAIM_NOSWAP; > > > mem_over_limit = mem_cgroup_from_res_counter(fail_res, > > > memsw); How about changing pre-charge size according to the loop count ? IMHO, it would be better to disable pre-charge at least in nr_retries==0 case, i.e. it is about to causing oom.
P.S. I will not be so active next week.
Thanks, Daisuke Nishimura.
| |