Web lists-archives.com

[Samba] Terrible share access performance (v.4.8 and current master branch)




Hello!

When I'm using qBittorrent [1] on Windows 10 with download location
set to remote Samba share on Arch Linux then it severely affects all
shares on that host, unrelated to disk where qBittorrent is actually
writing.

On Arch Linux that smbd process is using 100% of one CPU core time and
seems it's blocking because of lseek calls.

strace shows full of

lseek(47, 1420820480, SEEK_DATA)        = 1421344768
lseek(47, 1421344768, SEEK_HOLE)        = 1423441920
lseek(47, 1423441920, SEEK_DATA)        = 1423966208
lseek(47, 1423966208, SEEK_HOLE)        = 1425014784
lseek(47, 1425014784, SEEK_DATA)        = 1425539072
lseek(47, 1425539072, SEEK_HOLE)        = 1426063360
lseek(47, 1426063360, SEEK_DATA)        = 1426587648
lseek(47, 1426587648, SEEK_HOLE)        = 1427111936
lseek(47, 1427111936, SEEK_DATA)        = 1427636224
lseek(47, 1427636224, SEEK_HOLE)        = 1429733376
lseek(47, 1429733376, SEEK_DATA)        = 1430781952
lseek(47, 1430781952, SEEK_HOLE)        = 1431191552
lseek(47, 1431191552, SEEK_DATA)        = 1432879104
lseek(47, 1432879104, SEEK_HOLE)        = 1433403392
lseek(47, 1433403392, SEEK_DATA)        = 1433927680
lseek(47, 1433927680, SEEK_HOLE)        = 1434402816
lseek(47, 1434402816, SEEK_DATA)        = 1434451968
lseek(47, 1434451968, SEEK_HOLE)        = 1434976256
lseek(47, 1434976256, SEEK_DATA)        = 1435500544
lseek(47, 1435500544, SEEK_HOLE)        = 1436024832
lseek(47, 1436024832, SEEK_DATA)        = 1438121984
lseek(47, 1438121984, SEEK_HOLE)        = 1438646272
lseek(47, 1438646272, SEEK_DATA)        = 1439170560
lseek(47, 1439170560, SEEK_HOLE)        = 1439694848
lseek(47, 1439694848, SEEK_DATA)        = 1440743424
lseek(47, 1440743424, SEEK_HOLE)        = 1442316288
lseek(47, 1442316288, SEEK_DATA)        = 1443889152
...


% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 94.42   29.247198         449     65142           lseek
  1.13    0.350504          82      4285           writev
  0.60    0.185996          10     19194           geteuid
  0.60    0.185819          10     19194           getegid
  0.43    0.134625          15      8912           readv
  0.40    0.124905          12     10353        24 stat
  0.36    0.111773          17      6773      4183 getxattr
  0.33    0.102632          12      8922           setresuid
  0.31    0.097227          11      8922           setresgid
  0.27    0.083860          13      6659           epoll_pwait
  0.24    0.073222          15      4803         3 futex
  0.23    0.071162          11      6671           getpid
  0.21    0.066586          13      5136           setgroups
  0.14    0.044679          11      4057           read
  0.11    0.035451          14      2476           chdir
  0.08    0.026077          10      2700           getgroups
  0.07    0.021106          12      1768           fcntl
  0.01    0.003112          33        93           clone
  0.01    0.002433          10       233           fstat
  0.01    0.001825          10       186           rt_sigprocmask
  0.00    0.001099          15        75           close
  0.00    0.000780          16        50           openat
  0.00    0.000773          13        60           lstat
  0.00    0.000637          12        55           mprotect
  0.00    0.000598          11        55           mmap
  0.00    0.000474          13        36           newfstatat
  0.00    0.000453          21        22           getdents
  0.00    0.000377          29        13           sendmsg
  0.00    0.000270          14        20           socket
  0.00    0.000270          11        24           getcwd
  0.00    0.000246          12        20        10 connect
  0.00    0.000149          14        11           flock
  0.00    0.000142          24         6           utimensat
  0.00    0.000137          11        12           pread64
  0.00    0.000129          11        12           kill
  0.00    0.000117          15         8           open
  0.00    0.000019          19         1           brk
------ ----------- ----------- --------- --------- ----------------
100.00   30.976862                186959      4220 total


backtrace

0x00007fe85731114d in lseek64 () from /usr/lib/libpthread.so.0
Thread 1 (Thread 0x7fe8576fd840 (LWP 2894)):
#0  0x00007fe85731114d in lseek64 () from /usr/lib/libpthread.so.0
#1  0x00007fe856a0abdc in vfswrap_lseek () from
/usr/lib/samba/libsmbd-base-samba4.so
#2  0x00007fe856ad656f in smb2_ioctl_filesys () from
/usr/lib/samba/libsmbd-base-samba4.so
#3  0x00007fe856ad53ec in smbd_smb2_request_process_ioctl () from
/usr/lib/samba/libsmbd-base-samba4.so
#4  0x00007fe856ac6f73 in smbd_smb2_request_dispatch () from
/usr/lib/samba/libsmbd-base-samba4.so
#5  0x00007fe856ac7c40 in smbd_smb2_connection_handler () from
/usr/lib/samba/libsmbd-base-samba4.so
#6  0x00007fe85358241f in ?? () from /usr/lib/libtevent.so.0
#7  0x00007fe853580839 in ?? () from /usr/lib/libtevent.so.0
#8  0x00007fe85357cb9e in _tevent_loop_once () from /usr/lib/libtevent.so.0
#9  0x00007fe85357cdbc in tevent_common_loop_wait () from
/usr/lib/libtevent.so.0
#10 0x00007fe8535807d9 in ?? () from /usr/lib/libtevent.so.0
#11 0x00007fe856ab7998 in smbd_process () from
/usr/lib/samba/libsmbd-base-samba4.so
#12 0x00005560528caf9c in smbd_accept_connection ()
#13 0x00007fe85358241f in ?? () from /usr/lib/libtevent.so.0
#14 0x00007fe853580839 in ?? () from /usr/lib/libtevent.so.0
#15 0x00007fe85357cb9e in _tevent_loop_once () from /usr/lib/libtevent.so.0
#16 0x00007fe85357cdbc in tevent_common_loop_wait () from
/usr/lib/libtevent.so.0
#17 0x00007fe8535807d9 in ?? () from /usr/lib/libtevent.so.0
#18 0x00005560528c60d6 in main ()


I made a Ruby script (see attachment) to benchmark other share's
access time which is on different partition and physical disk than one
to which qBittorrent is writing.

When qBittorrent is downloading then for that other share on average
real time is 0.22 seconds but when it's not then it's 0.033 seconds
which is huge difference and very noticeable.

shares are hosted on Arch Linux with kernel 4.15.10 and just compiled
samba from git master branch (commit
a6054c01c29c2507e0d5a6aa110fee4fd5c5eeb9)
using BTRFS filesystem for all shares but different partitions for
qBittorrent writing and other shares.

client is Windows 10 (1709, build 16299.309)
qBittorrent v4.0.4


[1] https://www.qbittorrent.org/
-- 
To unsubscribe from this list go to the following URL and read the
instructions:  https://lists.samba.org/mailman/options/samba