> -----Original Message-----
> From: Jesper Dangaard Brouer [mailto:bro...@redhat.com]
> Sent: Tuesday, August 29, 2017 3:20 PM
> To: Florian Westphal
> Cc: liujian (CE); da...@davemloft.net; kuz...@ms2.inr.ac.ru;
> yoshf...@linux-ipv6.org; elena.reshet...@intel.com; eduma...@google.com;
> netdev@vger.kernel.org; Wangkefeng (Kevin); weiyongjun (A);
> bro...@redhat.com
> Subject: Re: Question about ip_defrag
>
> On Mon, 28 Aug 2017 16:00:32 +0200
> Florian Westphal <f...@strlen.de> wrote:
>
> > liujian (CE) <liujia...@huawei.com> wrote:
> > > Hi
> > >
> > > I checked our 3.10 kernel, we had backported all percpu_counter bug fix in
> lib/percpu_counter.c and include/linux/percpu_counter.h.
> > > And I check 4.13-rc6, also has the issue if NIC's rx cpu num big enough.
> > >
> > > > > > > the issue:
> > > > > > > Ip_defrag fail caused by frag_mem_limit reached
> 4M(frags.high_thresh).
> > > > > > > At this moment,sum_frag_mem_limit is about 10K.
> > >
> > > So should we change ipfrag high/low thresh to a reasonable value ?
> > > And if it is, is there a standard to change the value?
> >
> > Each cpu can have frag_percpu_counter_batch bytes rest doesn't know
> > about so with 64 cpus that is ~8 mbyte.
> >
> > possible solutions:
> > 1. reduce frag_percpu_counter_batch to 16k or so 2. make both low and
> > high thresh depend on NR_CPUS
>
> To me it looks like we/I have been using the wrong API for comparing against
> percpu_counters. I guess we should have used
> __percpu_counter_compare().
Are you means?
Change
if (frag_mem_limit(nf) > nf->low_thresh)
to
__percpu_counter_compare(&nf->mem, nf->low_thresh, frag_percpu_counter_batch)
> /*
> * Compare counter against given value.
> * Return 1 if greater, 0 if equal and -1 if less */ int
> __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch) {
> s64 count;
>
> count = percpu_counter_read(fbc);
> /* Check to see if rough count will be sufficient for comparison */
> if (abs(count - rhs) > (batch * num_online_cpus())) {
> if (count > rhs)
> return 1;
> else
> return -1;
> }
> /* Need to use precise count */
> count = percpu_counter_sum(fbc);
> if (count > rhs)
> return 1;
> else if (count < rhs)
> return -1;
> else
> return 0;
> }
> EXPORT_SYMBOL(__percpu_counter_compare);
>
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
