On Wed, Apr 01, 2015 at 01:17:19PM -0400, ira.weiny wrote:
> On Mon, Mar 23, 2015 at 11:17:49AM -0600, Jason Gunthorpe wrote:
> > On Sun, Mar 22, 2015 at 11:21:50AM +0200, Yuval Shaia wrote:
> > > On Sun, Mar 15, 2015 at 05:16:16PM +0200, Yuval Shaia wrote:
> > > > Hi,
> > > > I didn't got any further comments on this one.
> > > > Any idea why SG in CM is un-welcome?
> > > By mistake I sent a private mail only.
> > > Cc: Roland Dreier <[email protected]>
> > > Cc: Sean Hefty <[email protected]>
> > > Cc: Hal Rosenstock <[email protected]>
> > >
> > > Your advice would be very appreciated.
> >
> > I haven't looked in detail at the patch, but in principle, using S/G
> > when ever possible should be the default, even if this creates a
> > performance regression.
> >
> > It is well known that high order allocations are problematic in Linux
> > and should be avoided, and I also have seen systems blow up because of
> > high order IPoIB allocations.
> >
> > That said, there may be cases where S/G is not possible, you should
> > try and get Mellanox to comment if all their offloads work on all
> > their cards when S/G is used. Work may be required to resolve any of
> > these constraints. I'd like to belive there is some reason why we've
> > been doing high order allocations for so many years.
> >
> > FWIW, I would probably choose to default S/G over any other offload
> > acceleration.
>
> I concur with Jason's assessment.
>
> As Yann asked before:
>
> What hardware have you tested this on? Do you have any performance
> measurements? Or do you have a reproducer for some of the allocation issues
> which have been seen?
Tested on Mellanox MT26428. Have here also CX3, will update if there will be an
issue.
No impact on performances.
I did not try to reproduce the issue but people that do got this dump:
pr 7 09:33:30 dbnode kernel: Call Trace:
Apr 7 09:33:30 dbnode kernel: [<ffffffff810ddf74>]
__alloc_pages_nodemask+0x524/0x595
Apr 7 09:33:30 dbnode kernel: [<ffffffff8110da3f>] kmem_getpages+0x4f/0xf4
Apr 7 09:33:30 dbnode kernel: [<ffffffff8110dc12>] fallback_alloc+0x12e/0x1ce
Apr 7 09:33:30 dbnode kernel: [<ffffffff8110ddd3>]
____cache_alloc_node+0x121/0x134
Apr 7 09:33:30 dbnode kernel: [<ffffffff8110e3f3>]
kmem_cache_alloc_node_notrace+0x84/0xb9
Apr 7 09:33:30 dbnode kernel: [<ffffffff8110e46e>] __kmalloc_node+0x46/0x73
Apr 7 09:33:30 dbnode kernel: [<ffffffff813b9aa8>] ? __alloc_skb+0x72/0x13d
Apr 7 09:33:30 dbnode kernel: [<ffffffff813b9aa8>] __alloc_skb+0x72/0x13d
Apr 7 09:33:30 dbnode kernel: [<ffffffff813f2364>]
sk_stream_alloc_skb+0x3d/0xaf
Apr 7 09:33:30 dbnode kernel: [<ffffffff813f35b5>] tcp_sendmsg+0x176/0x6cf
Apr 7 09:33:30 dbnode kernel: [<ffffffff813b0d5f>] __sock_sendmsg+0x5e/0x67
Apr 7 09:33:30 dbnode kernel: [<ffffffff813b1644>] sock_sendmsg+0xcc/0xe5
Apr 7 09:33:30 dbnode kernel: [<ffffffff810b4d09>] ? delayacct_end+0x7d/0x88
Apr 7 09:33:30 dbnode kernel: [<ffffffff8104a3b0>] ?
delayacct_blkio_end+0x26/0x40
Apr 7 09:33:30 dbnode kernel: [<ffffffff81077030>] ?
autoremove_wake_function+0x0/0x3d
Apr 7 09:33:30 dbnode kernel: [<ffffffff81456f1d>] ? __wait_on_bit+0x6c/0x7c
Apr 7 09:33:30 dbnode kernel: [<ffffffff810d7b70>] ? sync_page+0x0/0x4d
Apr 7 09:33:30 dbnode kernel: [<ffffffff8111656e>] ?
__pfn_to_section+0x12/0x14
Apr 7 09:33:30 dbnode kernel: [<ffffffff811165a2>] ?
lookup_page_cgroup+0x32/0x48
Apr 7 09:33:30 dbnode kernel: [<ffffffff81100a61>] ? swap_entry_free+0x7a/0xf3
Apr 7 09:33:30 dbnode kernel: [<ffffffff8111c239>] ? fget_light+0x34/0x73
Apr 7 09:33:30 dbnode kernel: [<ffffffff813b0fcb>] ?
sockfd_lookup_light+0x20/0x58
Apr 7 09:33:30 dbnode kernel: [<ffffffff813b22cf>] sys_sendto+0x12f/0x171
Apr 7 09:33:30 dbnode kernel: [<ffffffff810a9d23>] ?
audit_syscall_entry+0x103/0x12f
Apr 7 09:33:30 dbnode kernel: [<ffffffff81011db2>]
system_call_fastpath+0x16/0x1b
>
> I can't comment on how this may affect Mellanox Hardware but it seems like it
> will work fine with Qib hardware.
>
> Ira
>
>
> >
> > Jason
> > --
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