Messages in this thread | | | Date | Sun, 4 Mar 2012 12:14:00 +0300 | From | Sergei Trofimovich <> | Subject | Re: [PATCHv 2] tcp: properly initialize tcp memory limits part 2 (fix nfs regression) |
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On Sat, 3 Mar 2012 20:27:17 -0300 Glauber Costa <glommer@parallels.com> wrote:
> On 03/03/2012 11:43 AM, Sergei Trofimovich wrote: > > On Sat, 3 Mar 2012 11:16:41 -0300 > > Glauber Costa<glommer@parallels.com> wrote: > > > >> On 03/02/2012 02:50 PM, Sergei Trofimovich wrote: > >>>>>> The change looks like a typo (division flipped to multiplication): > >>>>>>> limit = nr_free_buffer_pages() / 8; > >>>>>>> limit = nr_free_buffer_pages()<< (PAGE_SHIFT - 10); > >>>>> > >>>>> Hi, thanks for the reporting. It's not a typo. It was previously: > >>>>> sysctl_tcp_mem[1]<< (PAGE_SHIFT - 7). Looks like we need to do the > >>>>> limit check before shift the value. Please try the following patch, thanks. > >>>> > >>>> Still does not help. I test it by checking sha1sum of a large file over NFS > >>>> (small files seem to work simetimes): > >>>> > >>>> $ strace sha1sum /gentoo/distfiles/gcc-4.6.2.tar.bz2 > >>>> ... > >>>> open("/gentoo/distfiles/gcc-4.6.2.tar.bz2", O_RDONLY > >>>> <HUNG> > >>>> After a certain timeout dmesg gets odd spam: > >>>> [ 314.848094] nfs: server vmhost not responding, still trying > >>>> [ 314.848134] nfs: server vmhost not responding, still trying > >>>> [ 314.848145] nfs: server vmhost not responding, still trying > >>>> [ 314.957047] nfs: server vmhost not responding, still trying > >>>> [ 314.957066] nfs: server vmhost not responding, still trying > >>>> [ 314.957075] nfs: server vmhost not responding, still trying > >>>> [ 314.957085] nfs: server vmhost not responding, still trying > >>>> [ 314.957100] nfs: server vmhost not responding, still trying > >>>> [ 314.958023] nfs: server vmhost not responding, still trying > >>>> [ 314.958035] nfs: server vmhost not responding, still trying > >>>> [ 314.958044] nfs: server vmhost not responding, still trying > >>>> [ 314.958054] nfs: server vmhost not responding, still trying > >>>> > >>>> looks like bogus messages. Might be relevant to mishandled timings > >>>> somewhere else or a bug in nfs code. > >>> > >>> And after 120 seconds hung tasks shows it might be an OOM issue > >>> Likely caused by patch, as it's a 2GB RAM +4GB swap amd64 box > >>> not running anything heavy: > >> > >> That is a bit weird. > >> > >> First because with Jason's patch, we should end up with the very same > >> calculation, at the same exact order, as it was in older kernels. > >> Second, because by shifting<< 10, you should be ending up with very > >> small numbers, effectively having tcp_rmem[1] == tcp_rmem[2], and the > >> same for wmem. > >> > >> Can you share which numbers you end up with at > >> /proc/sys/net/ipv4/tcp_{r,w}mem ? > >> > > > > Sure: > > > > $ cat /proc/sys/net/ipv4/tcp_{r,w}mem > > 4096 87380 1999072 > > 4096 16384 1999072 > > > Sergei, > > Sorry for not being clearer. I was expecting you'd post those values > both in the scenario in which you see the bug, and in the scenario you > don't.
Ah, I see. Sorry. Patches are on top of v3.3-rc5-166-g1f033c1. Buggy one: > - limit = nr_free_buffer_pages() << (PAGE_SHIFT - 10); > - limit = max(limit, 128UL); > + limit = nr_free_buffer_pages() / 8; > + limit = max(limit, 128UL) << (PAGE_SHIFT - 7); > max_share = min(4UL*1024*1024, limit); > + printk(KERN_INFO "TCP: max_share=%u\n", max_share); $ cat /proc/sys/net/ipv4/tcp_{r,w}mem 4096 87380 1999072 4096 16384 1999072
Working one: > - limit = nr_free_buffer_pages() << (PAGE_SHIFT - 10); > + limit = nr_free_buffer_pages() >> (PAGE_SHIFT - 10); > limit = max(limit, 128UL); > max_share = min(4UL*1024*1024, limit); > + printk(KERN_INFO "TCP: max_share=%u\n", max_share); $ cat /proc/sys/net/ipv4/tcp_{r,w}mem 4096 87380 124942 4096 16384 124942
> > Nothing special with NFS nere, so I guess it uses UDP. > > TCP works fine on machine (I do everything via SSH). > > Can you confirm that? If you're using nfs through udp, it makes > even less sense that the default values of tcp sock mem will harm > you. So it might be a bug somewhere else...
Rechecked with tcpdump. It uses TCP.
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Sergei [unhandled content-type:application/pgp-signature] | |