[Samba] Samba -> WinXP: slow transfers, partial solution
Alexander Tsvyashchenko
lists at ndl.kiev.ua
Sat Apr 14 15:33:07 GMT 2007
Hello All,
I'm running Samba 3.0.24 as PDC and file server on Gentoo Linux,
AMD64, 2.6.19 kernel, 100MBit/s network, and experience quite slow
file transfers from Samba to WinXP SP2 clients: the speed is varying,
but is about 1-2Mb/s at best.
I spent quite some time investigating the issue, here are the
intermediate results:
1) This happens only when transferring _from_ _Samba_ to _WinXP_.
All other combinations are unaffected:
a) Transferring from WinXP to Samba server is at 10Mb/s.
b) Transfering to/from Samba server from Gentoo Linux on the same PC
where WinXP is installed (so, completely the same hardware and
connection) is also at normal speed.
c) Transferring to/from WinXP to the server where Samba is installed
using any other protocol (such as HTTPS or SCP) is also at normal speed.
2) CPU is at almost idle level both at client and server, so it's not
the issue.
3) If there is any other network activity, transfer speed is increased
up to normal level: f.e. doing two simulteneous transfers from Samba
server to WinXP client gives 5Mb/s at each transfer, as expected.
4) Running tcpdump on server while the transfer is performed improves
transfer speed in about 1.5 - 3 times, but still not to the normal
speed.
5) Playing with "socket options" does not give any results.
Specifically, using advices from the article
http://www.dd.iij4u.or.jp/~okuyamak/Documents/tuning.english.html
about SO_SNDBUF does not improve situation (but read below).
6) tcpdump + tcptrace show that there are a lot of retransmissions,
see dumps below.
7) I've tested several WinXP clients with different hardware, all with
the same results.
8) Samba logs looks normal to me, nothing special.
Points (3) and (5), and also the article about SO_SNDBUF tuning gave
me an idea that there might be smth wrong with ACKs sent from WinXP.
I've tried to search for problems with ACK delays in WinXP and found
the following articles:
http://support.microsoft.com/kb/328890
http://support.microsoft.com/kb/321098
Based on them, I've done the following changes in WinXP registry:
- set TcpAckFrequency to 1 to switch off delayed ACKs
- set TcpDelAckTicks to 0 to disable delayed ACKs timer
These changes did not help on their own. But combining them with the
change of SO_SNDBUF to 1500 suddenly improved the speeds up to about 6
Mb/s!
It appeared that with these registry changes, setting SO_SNDBUF to any
value in the range 1404 - 1872 gives the same speed of 6.0 - 6.4 Mb/s,
while changing it even one byte lower / higher immmediately drops the
speed to less than 1Mb/s.
However, while this is partial solution I could live with, this is
still not the normal speed, so I still would like to find the way to
bring it to normal values.
It seems that I'm not the only one who have similar problems: see BUGs
2117 and 3706 in Bugzilla, and discussion at Gentoo mailing list:
http://forums.gentoo.org/viewtopic-p-2820556.html
Please, let me know if any other information may be needed or if there
are any other tests I can do to pin down the problem ...
I'm attaching tcptrace logs for several sessions
(all transfers are from Samba server to WinXP with registry changes applied,
all transfers are done with the same file of the size 338Mb).
1) Samba -> WinXP without SO_SNDBUF set.
(note that due to the "tcpdump effect" the speed is higher than in reality,
also please note big number of retransmits)
================================
TCP connection 3:
host e: ***client***:1314
host f: ***server***:445
complete conn: no (SYNs: 0) (FINs: 0)
first packet: Sat Apr 14 15:05:57.502839 2007
last packet: Sat Apr 14 15:07:53.234397 2007
elapsed time: 0:01:55.731558
total packets: 425593
filename: snd_buf_off.log
e->f: f->e:
total packets: 175858 total packets: 249735
ack pkts sent: 175858 ack pkts sent: 249735
pure acks sent: 164954 pure acks sent: 8
sack pkts sent: 0 sack pkts sent: 0
dsack pkts sent: 0 dsack pkts sent: 0
max sack blks/ack: 0 max sack blks/ack: 0
unique bytes sent: 690320 unique bytes sent: 356048963
actual data pkts: 10904 actual data pkts: 249727
actual data bytes: 690320 actual data bytes: 356319077
rexmt data pkts: 0 rexmt data pkts: 195
rexmt data bytes: 0 rexmt data bytes: 270114
zwnd probe pkts: 0 zwnd probe pkts: 0
zwnd probe bytes: 0 zwnd probe bytes: 0
outoforder pkts: 0 outoforder pkts: 0
pushed data pkts: 10904 pushed data pkts: 10982
SYN/FIN pkts sent: 0/0 SYN/FIN pkts sent: 0/0
urgent data pkts: 0 pkts urgent data pkts: 0 pkts
urgent data bytes: 0 bytes urgent data bytes: 0 bytes
mss requested: 0 bytes mss requested: 0 bytes
max segm size: 170 bytes max segm size: 1460 bytes
min segm size: 40 bytes min segm size: 39 bytes
avg segm size: 63 bytes avg segm size: 1426 bytes
max win adv: 65535 bytes max win adv: 24656 bytes
min win adv: 64099 bytes min win adv: 15008 bytes
zero win adv: 0 times zero win adv: 0 times
avg win adv: 65464 bytes avg win adv: 24655 bytes
max owin: 171 bytes max owin: 61504 bytes
min non-zero owin: 1 bytes min non-zero owin: 1 bytes
avg owin: 4 bytes avg owin: 28273 bytes
wavg owin: 0 bytes wavg owin: 16041 bytes
initial window: 138 bytes initial window: 0 bytes
initial window: 1 pkts initial window: 0 pkts
ttl stream length: NA ttl stream length: NA
missed data: NA missed data: NA
truncated data: 537664 bytes truncated data: 352822899 bytes
truncated packets: 10904 pkts truncated packets: 249727 pkts
data xmit time: 115.730 secs data xmit time: 115.730 secs
idletime max: 661.6 ms idletime max: 661.9 ms
throughput: 5965 Bps throughput: 3076507 Bps
================================
2) Samba -> WinXP without SO_SNDBUF set, two simultaneous transfers
(note there are no retransmits at all)
================================
TCP connection 1:
host a: ***client***:1314
host b: ***server***:445
complete conn: no (SYNs: 0) (FINs: 0)
first packet: Sat Apr 14 15:35:27.213438 2007
last packet: Sat Apr 14 15:36:31.474766 2007
elapsed time: 0:01:04.261328
total packets: 800651
filename: simult_snd_buf_off.log
a->b: b->a:
total packets: 326843 total packets: 473808
ack pkts sent: 326843 ack pkts sent: 473808
pure acks sent: 306750 pure acks sent: 31
sack pkts sent: 0 sack pkts sent: 2
dsack pkts sent: 0 dsack pkts sent: 1
max sack blks/ack: 0 max sack blks/ack: 1
unique bytes sent: 1266917 unique bytes sent: 658967341
actual data pkts: 20093 actual data pkts: 473777
actual data bytes: 1266980 actual data bytes: 658967341
rexmt data pkts: 1 rexmt data pkts: 0
rexmt data bytes: 63 rexmt data bytes: 0
zwnd probe pkts: 0 zwnd probe pkts: 0
zwnd probe bytes: 0 zwnd probe bytes: 0
outoforder pkts: 0 outoforder pkts: 0
pushed data pkts: 20093 pushed data pkts: 25922
SYN/FIN pkts sent: 0/0 SYN/FIN pkts sent: 0/0
urgent data pkts: 0 pkts urgent data pkts: 0 pkts
urgent data bytes: 0 bytes urgent data bytes: 0 bytes
mss requested: 0 bytes mss requested: 0 bytes
max segm size: 148 bytes max segm size: 1460 bytes
min segm size: 40 bytes min segm size: 39 bytes
avg segm size: 63 bytes avg segm size: 1390 bytes
max win adv: 65535 bytes max win adv: 24656 bytes
min win adv: 51724 bytes min win adv: 24656 bytes
zero win adv: 0 times zero win adv: 0 times
avg win adv: 65472 bytes avg win adv: 24656 bytes
max owin: 18446744073709551554 bytes max owin:
69822 bytes
min non-zero owin: 1 bytes min non-zero owin: 1 bytes
avg owin: 7 bytes avg owin: 45958 bytes
wavg owin: 7750572630405 bytes wavg owin:
50450 bytes
initial window: 63 bytes initial window: 0 bytes
initial window: 1 pkts initial window: 0 pkts
ttl stream length: NA ttl stream length: NA
missed data: NA missed data: NA
truncated data: 985678 bytes truncated data: 652334463 bytes
truncated packets: 20093 pkts truncated packets: 473777 pkts
data xmit time: 64.257 secs data xmit time: 64.257 secs
idletime max: 2790.4 ms idletime max: 2790.6 ms
throughput: 19715 Bps throughput: 10254493 Bps
================================
3) Samba -> WinXP with SO_SNDBUF set to 1500.
================================
TCP connection 3:
host e: ***client***:3878
host f: ***server***:445
complete conn: no (SYNs: 0) (FINs: 0)
first packet: Sat Apr 14 18:18:59.800152 2007
last packet: Sat Apr 14 18:20:05.035874 2007
elapsed time: 0:01:05.235721
total packets: 501414
filename: snd_buf_on.log
e->f: f->e:
total packets: 251898 total packets: 249516
ack pkts sent: 251898 ack pkts sent: 249516
pure acks sent: 240994 pure acks sent: 10
sack pkts sent: 0 sack pkts sent: 0
dsack pkts sent: 0 dsack pkts sent: 0
max sack blks/ack: 0 max sack blks/ack: 0
unique bytes sent: 690320 unique bytes sent: 356048963
actual data pkts: 10904 actual data pkts: 249506
actual data bytes: 690320 actual data bytes: 356052623
rexmt data pkts: 0 rexmt data pkts: 20
rexmt data bytes: 0 rexmt data bytes: 3660
zwnd probe pkts: 0 zwnd probe pkts: 0
zwnd probe bytes: 0 zwnd probe bytes: 0
outoforder pkts: 0 outoforder pkts: 0
pushed data pkts: 10904 pushed data pkts: 10923
SYN/FIN pkts sent: 0/0 SYN/FIN pkts sent: 0/0
urgent data pkts: 0 pkts urgent data pkts: 0 pkts
urgent data bytes: 0 bytes urgent data bytes: 0 bytes
mss requested: 0 bytes mss requested: 0 bytes
max segm size: 170 bytes max segm size: 1460 bytes
min segm size: 40 bytes min segm size: 39 bytes
avg segm size: 63 bytes avg segm size: 1427 bytes
max win adv: 65535 bytes max win adv: 24656 bytes
min win adv: 64081 bytes min win adv: 24656 bytes
zero win adv: 0 times zero win adv: 0 times
avg win adv: 65483 bytes avg win adv: 24656 bytes
max owin: 171 bytes max owin: 2921 bytes
min non-zero owin: 1 bytes min non-zero owin: 1 bytes
avg owin: 3 bytes avg owin: 2805 bytes
wavg owin: 0 bytes wavg owin: 765 bytes
initial window: 138 bytes initial window: 0 bytes
initial window: 1 pkts initial window: 0 pkts
ttl stream length: NA ttl stream length: NA
missed data: NA missed data: NA
truncated data: 537664 bytes truncated data: 352559539 bytes
truncated packets: 10904 pkts truncated packets: 249506 pkts
data xmit time: 65.235 secs data xmit time: 65.235 secs
idletime max: 2000.5 ms idletime max: 2000.8 ms
throughput: 10582 Bps throughput: 5457883 Bps
================================
4) Transfer from Samba server to WinXP using SCP protocol.
================================
TCP connection 4:
host g: ***client***:1501
host h: ***server***:22
complete conn: no (SYNs: 0) (FINs: 2)
first packet: Sat Apr 14 15:25:26.305071 2007
last packet: Sat Apr 14 15:25:57.316420 2007
elapsed time: 0:00:31.011348
total packets: 436782
filename: scp.log
g->h: h->g:
total packets: 179196 total packets: 257586
ack pkts sent: 179196 ack pkts sent: 257586
pure acks sent: 174818 pure acks sent: 13
sack pkts sent: 0 sack pkts sent: 0
dsack pkts sent: 0 dsack pkts sent: 0
max sack blks/ack: 0 max sack blks/ack: 0
unique bytes sent: 210208 unique bytes sent: 356544464
actual data pkts: 4377 actual data pkts: 257572
actual data bytes: 210208 actual data bytes: 356544464
rexmt data pkts: 0 rexmt data pkts: 0
rexmt data bytes: 0 rexmt data bytes: 0
zwnd probe pkts: 0 zwnd probe pkts: 0
zwnd probe bytes: 0 zwnd probe bytes: 0
outoforder pkts: 0 outoforder pkts: 0
pushed data pkts: 4377 pushed data pkts: 21912
SYN/FIN pkts sent: 0/1 SYN/FIN pkts sent: 0/1
urgent data pkts: 0 pkts urgent data pkts: 0 pkts
urgent data bytes: 0 bytes urgent data bytes: 0 bytes
mss requested: 0 bytes mss requested: 0 bytes
max segm size: 96 bytes max segm size: 1460 bytes
min segm size: 32 bytes min segm size: 28 bytes
avg segm size: 48 bytes avg segm size: 1384 bytes
max win adv: 65535 bytes max win adv: 8272 bytes
min win adv: 22451 bytes min win adv: 8272 bytes
zero win adv: 0 times zero win adv: 0 times
avg win adv: 62839 bytes avg win adv: 8272 bytes
max owin: 97 bytes max owin: 65501 bytes
min non-zero owin: 1 bytes min non-zero owin: 1 bytes
avg owin: 5 bytes avg owin: 50602 bytes
wavg owin: 0 bytes wavg owin: 56657 bytes
initial window: 80 bytes initial window: 0 bytes
initial window: 1 pkts initial window: 0 pkts
ttl stream length: NA ttl stream length: NA
missed data: NA missed data: NA
truncated data: 148930 bytes truncated data: 352938456 bytes
truncated packets: 4377 pkts truncated packets: 257572 pkts
data xmit time: 31.010 secs data xmit time: 31.004 secs
idletime max: 101.0 ms idletime max: 103.8 ms
throughput: 6778 Bps throughput: 11497225 Bps
================================
Thanks!
Good luck! Alexander
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