IBM pSeries 5.12 Dropped switch packets

pshpstuningguidew p040105.doc Page 24

MPCI: sends = 14

MPCI: sendsComplete = 14

MPCI: sendWaitsComplete = 17

MPCI: recvs = 17

MPCI: recvWaitsComplete = 13

MPCI: earlyArrivals = 5

MPCI: earlyArrivalsMatched = 5

MPCI: lateArri va ls = 8

MPCI: shoves = 10

MPCI: pulls = 13

MPCI: threadedLockYields = 0

MPCI: unorderedMsgs = 0

LAPI: Tot_dup_pkt_cnt=0

LAPI: Tot_retrans_pkt_cnt=0

LAPI: Tot_gho_pkt_cnt=0

LAPI: Tot_pkt_sent_cnt=14

LAPI: Tot_pkt_recv_cnt=15

LAPI: Tot_data_sent=4194

LAPI: Tot_data_recv=3511

5.12 Dropped switch packets

Lower than expected performance can be caused by dropped packets on the HPS switch. Packets

sent over a s wit ch interfa ce can be dropp ed in severa l wa ys, as descr ibed in the fo llowing

sections.

Packets are s o metimes dropp ed at one of th e e n dpoints of t h e packet tra nsfer. In this ca se, you

should be ab l e to run AIX 5L co mmands to se e s ome evidenc e on the endp oint that dr opped the

packet. For examp le, ru n /usr/sni/sni.snap -l {adapter_number} to get the

correct endp oint data. This is best ta ke n b oth befor e a nd after re-cr eating the pr oblem. The

sni.snap creates a new archive in /var/adm/sni/snaps. For exampl e, /usr/sni/sni.snap -

l 1 produces a hostname.ad apter_no.timestamp file such as

/var/adm/sni/snaps/c704f2n01.1.041118122825.FEFE5.sni.snap.tar.Z.

For IP traffic, looking at netstat -D data is a good place to start:

netstat -D

Source Ipkts Opkts Idrops Odrops

[. . .]

sn_dmx0 156495 N/A 0 N/A

sn_dmx1 243602 N/A 0 N/A

sn_if0 156495 140693 0 0

sn_if1 243602 241028 0 13

ml_if0 0 98 0 10

The ifsn_dump command provides interface-layer statistics for the sni interfaces. This tool helps

you diagnose packet drops seen in netstat -D and also prints some drops that are not shown under

netstat.