From: Namjae Jeon <linkinjeon@kernel.org>
To: David Howells <dhowells@redhat.com>
Cc: Steve French <smfrench@gmail.com>, CIFS <linux-cifs@vger.kernel.org>
Subject: Re: ksmbd threads eating masses of cputime
Date: Wed, 1 Jun 2022 09:56:17 +0900 [thread overview]
Message-ID: <CAKYAXd_9jw69iKPBvuE4DxdpwcH2H90h3NQDQ7nyxzbTnEcirg@mail.gmail.com> (raw)
In-Reply-To: <833010.1654031136@warthog.procyon.org.uk>
2022-06-01 6:05 GMT+09:00, David Howells <dhowells@redhat.com>:
> Hi Namjae,
>
> Steve says I should show this to you.
>
> My server box that I'm using to do cifs-over-RDMA testing is running really
> slowly because it has about 30 ksmbd thread hogging the cpus:
>
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+
> COMMAND
> 19993 root 20 0 0 0 0 R 14.3 0.0 910:06.02
> ksmbd:r5445
> 20048 root 20 0 0 0 0 R 14.3 0.0 896:19.22
> ksmbd:r5445
> 20052 root 20 0 0 0 0 R 14.3 0.0 901:51.52
> ksmbd:r5445
> 20053 root 20 0 0 0 0 R 14.3 0.0 904:20.84
> ksmbd:r5445
> 20056 root 20 0 0 0 0 R 14.3 0.0 910:39.38
> ksmbd:r5445
> 20095 root 20 0 0 0 0 R 14.3 0.0 901:28.48
> ksmbd:r5445
> 20097 root 20 0 0 0 0 R 14.3 0.0 910:02.19
> ksmbd:r5445
> 20103 root 20 0 0 0 0 R 14.3 0.0 912:13.18
> ksmbd:r5445
> 20105 root 20 0 0 0 0 R 14.3 0.0 908:46.76
> ksmbd:r5445
> ...
>
>
> I tried to shut them down with "ksmbd.control -s", but that just hung and
> the
> threads are still running. I captured a stack trace from one of them
> through
> /proc:
>
> [root@carina ~]# cat /proc/20052/stack
> [<0>] ksmbd_conn_handler_loop+0x181/0x200 [ksmbd]
> [<0>] kthread+0xe8/0x110
> [<0>] ret_from_fork+0x22/0x30
>
> Note that nothing is currently mounted from the server and it is getting no
> incoming packets.
Okay, How do you reproduce this problem ? Did you run xfsftests
against ksmbd RDMA ?
>
> Looking at the loop in ksmbd_conn_handler_loop(), it seems to be
> busy-waiting
> - unless kernel_recvmsg() is doing that? In the TCP transport, if
> kernel_recvmsg() isn't waiting, but returns -EAGAIN, it will sleep for
> 1-2ms
> and then go round again... and again... and again - and all 30 threads
> would
> be doing that.
Okay, we need to add maximum retry count for that case.
but when I check kernel thread name in your top message, It is RDMA connection.
So smb_direct_read() is used in ksmbd_conn_handler_loop().
I'd like to reproduce the problem to figure out where the problem is.
Can I try to reproduce it with soft-iWARP and xfstests?
>
>
> Btw in:
>
> ret = kernel_accept(iface->ksmbd_socket, &client_sk,
> O_NONBLOCK);
>
> that should be SOCK_NONBLOCK, I think.
Ah, I found that normally it is O_NONBLOCK but there are different
value for some arch.
I will change it. Thanks for pointing out:)
/include/linux/net.h
#ifndef SOCK_NONBLOCK
#define SOCK_NONBLOCK O_NONBLOCK
#endif
/arch/alpha/include/asm/socket.h
#define SOCK_NONBLOCK 0x40000000
>
> Also:
>
> [root@carina ~]# ksmbd.control --shutdown
> Usage: ksmbd.control
> -s | --shutdown
> ...
>
> that looks like it doesn't handle the advertised long parameters.
I will fix it:)
Thanks!
>
>
next prev parent reply other threads:[~2022-06-01 0:56 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-31 21:05 ksmbd threads eating masses of cputime David Howells
2022-06-01 0:56 ` Namjae Jeon [this message]
2022-06-01 8:40 ` David Howells
2022-06-02 23:50 ` Namjae Jeon
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