On 17.08.2012 21:18, J. Bruce Fields wrote:
> On Fri, Aug 17, 2012 at 09:12:38PM +0400, Michael Tokarev wrote:
[]
>> So we're calling svc_recv in a tight loop, eating
>> all available CPU. (The above is with just 2 nfsd
>> threads).
>>
>> Something is definitely wrong here. And it happens mure more
>> often after the mentioned commit (f03d78db65085).
>
> Oh, neat. Hm. That commit doesn't really sound like the cause, then.
> Is that busy-looping reproduceable on kernels before that commit?
Note I bisected this issue to this commit. I haven't seen it
happening before this commit, and reverting it from 3.0 or 3.2
kernel makes the problem to go away.
I guess it is looping there:
net/sunrpc/svc_xprt.c:svc_recv()
...
len = 0;
...
if (test_bit(XPT_LISTENER, &xprt->xpt_flags)) {
...
} else if (xprt->xpt_ops->xpo_has_wspace(xprt)) { <=== here -- has no wspace due to memory...
... len = <something>
}
/* No data, incomplete (TCP) read, or accept() */
if (len == 0 || len == -EAGAIN)
goto out;
...
out:
rqstp->rq_res.len = 0;
svc_xprt_release(rqstp);
return -EAGAIN;
}
I'm trying to verify this theory...
/mjt
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