svn commit: r333744 - in head/sys: kern sys

Peter Holm peter at holm.cc
Wed Jun 6 19:03:57 UTC 2018


On Thu, May 17, 2018 at 05:59:35PM +0000, Matt Macy wrote:
> Author: mmacy
> Date: Thu May 17 17:59:35 2018
> New Revision: 333744
> URL: https://svnweb.freebsd.org/changeset/base/333744
> 
> Log:
>   AF_UNIX: make unix socket locking finer grained
>   
>   This change moves to using a reference count across lock drop / reacquire
>   to guarantee liveness.
>   
>   Currently sends on unix sockets contend heavily on read locking the list lock.
>   unix1_processes in will-it-scale peaks at 6 processes and then declines.
>   
>   With this change I get a substantial improvement in number of operations per second
>   with 96 processes:
>   
>   x before
>   + after
>       N           Min           Max        Median           Avg        Stddev
>   x  11       1688420       1696389       1693578     1692766.3     2971.1702
>   +  10      63417955      71030114      70662504      69576423     2374684.6
>   Difference at 95.0% confidence
>           6.78837e+07 +/- 1.49463e+06
>           4010.22% +/- 88.4246%
>           (Student's t, pooled s = 1.63437e+06)
>   
>   And even for 2 processes shows a ~18% improvement.
>   "Small" iron changes (1, 2, and 4 processes):
>   
>   x before1
>   + after1.2
>   +------------------------------------------------------------------------+
>   |                                                                  +     |
>   |                                                           x      +     |
>   |                                                           x      +     |
>   |                                                           x      +     |
>   |                                                           x     ++     |
>   |                                                          xx     ++     |
>   |x                                                       x xx     ++     |
>   |                                  |__________________A_____M_____AM____||
>   +------------------------------------------------------------------------+
>       N           Min           Max        Median           Avg        Stddev
>   x  10       1131648       1197750     1197138.5     1190369.3     20651.839
>   +  10       1203840       1205056       1204919     1204827.9     353.27404
>   Difference at 95.0% confidence
>           14458.6 +/- 13723
>           1.21463% +/- 1.16683%
>           (Student's t, pooled s = 14605.2)
>   
>   x before2
>   + after2.2
>   +------------------------------------------------------------------------+
>   |                                                                       +|
>   |                                                                       +|
>   |                                                                       +|
>   |                                                                       +|
>   |                                                                       +|
>   |                                                                       +|
>   |           x                                                           +|
>   |           x                                                           +|
>   |         x xx                                                          +|
>   |x        xxxx                                                          +|
>   |      |___AM_|                                                         A|
>   +------------------------------------------------------------------------+
>       N           Min           Max        Median           Avg        Stddev
>   x  10       1972843       2045866     2038186.5     2030443.8     21367.694
>   +  10       2400853       2402196     2401043.5     2401172.7     385.40024
>   Difference at 95.0% confidence
>           370729 +/- 14198.9
>           18.2585% +/- 0.826943%
>           (Student's t, pooled s = 15111.7)
>   
>   x before4
>   + after4.2
>       N           Min           Max        Median           Avg        Stddev
>   x  10       3986994       3991728     3990137.5     3989985.2     1300.0164
>   +  10       4799990       4806664     4806116.5       4805194     1990.6625
>   Difference at 95.0% confidence
>           815209 +/- 1579.64
>           20.4314% +/- 0.0421713%
>           (Student's t, pooled s = 1681.19)
>   
>   Tested by: pho
>   Reported by:	mjg
>   Approved by:	sbruno
>   Sponsored by:	Limelight Networks
>   Differential Revision:	https://reviews.freebsd.org/D15430
> 
> Modified:
>   head/sys/kern/uipc_usrreq.c
>   head/sys/sys/unpcb.h
> 
> Modified: head/sys/kern/uipc_usrreq.c
> ==============================================================================
> --- head/sys/kern/uipc_usrreq.c	Thu May 17 17:57:41 2018	(r333743)

This commit seems to cause this:

20180606 20:44:37 all (1/1): datagram.sh
panic: _mtx_lock_sleep: recursed on non-recursive mutex unp_mtx @ ../../../kern/uipc_usrreq.c:354

cpuid = 91
time = 1528310678
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00f3a2bcd0
vpanic() at vpanic+0x1a3/frame 0xfffffe00f3a2bd30
doadump() at doadump/frame 0xfffffe00f3a2bdb0
__mtx_lock_sleep() at __mtx_lock_sleep+0x49d/frame 0xfffffe00f3a2be30
__mtx_lock_flags() at __mtx_lock_flags+0xf9/frame 0xfffffe00f3a2be80
unp_connectat() at unp_connectat+0x2ec/frame 0xfffffe00f3a2c110
soconnectat() at soconnectat+0xe8/frame 0xfffffe00f3a2c160
kern_connectat() at kern_connectat+0x10f/frame 0xfffffe00f3a2c1c0
sys_connect() at sys_connect+0x77/frame 0xfffffe00f3a2c200
amd64_syscall() at amd64_syscall+0x2a7/frame 0xfffffe00f3a2c330
fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe00f3a2c330
--- syscall (98, FreeBSD ELF64, sys_connect), rip = 0x80040081a, rsp = 0x7fffffffe2e8, rbp = 0x7fffffffe770 ---
KDB: enter: panic
[ thread pid 1276 tid 100966 ]
Stopped at      kdb_enter+0x3b: movq    $0,kdb_why
db> x/s version
version:        FreeBSD 12.0-CURRENT #0 r333744: Wed Jun  6 20:35:18 CEST 2018\012    pho at flix1a.netperf.freebsd.org:/usr/src/sys/amd64/compile/PHO\012
db> 

The stack trace is different on HEAD:

panic: mutex unp not owned at ../../../kern/uipc_usrreq.c:879
cpuid = 47
time = 1528311629
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe00ee593ca0
vpanic() at vpanic+0x1a3/frame 0xfffffe00ee593d00
panic() at panic+0x43/frame 0xfffffe00ee593d60
__mtx_assert() at __mtx_assert+0xb4/frame 0xfffffe00ee593d70
uipc_disconnect() at uipc_disconnect+0x93/frame 0xfffffe00ee593dc0
soclose() at soclose+0xa5/frame 0xfffffe00ee593e30
closef() at closef+0x1f5/frame 0xfffffe00ee593ec0
fdescfree_fds() at fdescfree_fds+0x90/frame 0xfffffe00ee593f10
fdescfree() at fdescfree+0x480/frame 0xfffffe00ee593fd0
exit1() at exit1+0x500/frame 0xfffffe00ee594040
sigexit() at sigexit+0xae8/frame 0xfffffe00ee594220
postsig() at postsig+0x1cf/frame 0xfffffe00ee5942f0
ast() at ast+0x4b8/frame 0xfffffe00ee594330
doreti_ast() at doreti_ast+0x1f/frame 0x7fffffffe760
KDB: enter: panic
[ thread pid 1013 tid 100834 ]
Stopped at      kdb_enter+0x3b: movq    $0,kdb_why
db> x/s version
version:        FreeBSD 12.0-CURRENT #0 r334723: Wed Jun  6 20:53:32 CEST 2018\012    pho at flix1a.netperf.freebsd.org:/usr/src/sys/amd64/compile/PHO\012
db> 

- Peter


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