[c-nsp] cisco buffer misses

[Pete Lumbis]

The output of show proc mem is not related to traffic forwarding on
hardware platforms like the 3650. Those are only for what software is
doing. I believe a miss is when we want a buffer of size X and there are no
more buffers of that size and use the next larger size. I know a lot of
this is covered in the Cisco IOS Architectures and CEF books.

Output drops, if qos is not configured, is due to either port or fabric
over subscription. You'll see output drops on multiple interfaces if it is
fabric/backplane. Most likely this is due to bursts destined to this single
port.

On Thursday, April 18, 2013, Michael Sprouffske wrote:

> Could someone give me some insight as to what is causing the misses?  I'm
> currently researching this on the inter webs.  I also notice an interface
> with several drops as well.
>
>
>
>
> model: WS-C3750X-24T-S
>
>
>
> Buffer elements:
>      1061 in free list (500 max allowed)
>      3479036431 hits, 0 misses, 1024 created
>
> Public buffer pools:
> Small buffers, 104 bytes (total 50, permanent 50, peak 119 @ 7w0d):
>      49 in free list (20 min, 150 max allowed)
>      1712506149 hits, 23 misses, 69 trims, 69 created
>      0 failures (0 no memory)
> Middle buffers, 600 bytes (total 25, permanent 25, peak 85 @ 7w0d):
>      23 in free list (10 min, 150 max allowed)
>      167702 hits, 58 misses, 174 trims, 174 created
>      0 failures (0 no memory)
> Big buffers, 1536 bytes (total 50, permanent 50, peak 119 @ 7w0d):
>      50 in free list (5 min, 150 max allowed)
>      244703400 hits, 39 misses, 117 trims, 117 created
>      0 failures (0 no memory)
> VeryBig buffers, 4520 bytes (total 16, permanent 10, peak 16 @ 7w0d):
>      0 in free list (0 min, 100 max allowed)
>      59 hits, 3 misses, 1429 trims, 1435 created
>      0 failures (0 no memory)
> Large buffers, 5024 bytes (total 0, permanent 0):
>      0 in free list (0 min, 10 max allowed)
>      0 hits, 0 misses, 0 trims, 0 created
>      0 failures (0 no memory)
> Huge buffers, 18024 bytes (total 4, permanent 0, peak 7 @ 7w0d):
>      4 in free list (0 min, 4 max allowed)
>      145363512 hits, 412449 misses, 822729 trims, 822733 created
>      0 failures (0 no memory)
>
>
>
>
> GigabitEthernet1/0/11 is up, line protocol is up (connected)
>   Hardware is Gigabit Ethernet, address is 649e.f3e2.7b8b (bia
> 649e.f3e2.7b8b)
>   Description: server ports
>   MTU 9000 bytes, BW 100000 Kbit, DLY 100 usec,
>      reliability 255/255, txload 1/255, rxload 1/255
>   Encapsulation ARPA, loopback not set
>   Keepalive set (10 sec)
>   Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX
>   input flow-control is off, output flow-control is unsupported
>   ARP type: ARPA, ARP Timeout 04:00:00
>   Last input 00:00:16, output 00:00:01, output hang never
>   Last clearing of "show interface" counters never
>   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 54011
>   Queueing strategy: fifo
>   Output queue: 0/40 (size/max)
>   5 minute input rate 0 bits/sec, 0 packets/sec
>   5 minute output rate 49000 bits/sec, 28 packets/sec
>      837676 packets input, 118543994 bytes, 0 no buffer
>      Received 492811 broadcasts (481207 multicasts)
>      0 runts, 0 giants, 0 throttles
>      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
>      0 watchdog, 481207 multicast, 0 pause input
>      0 input packets with dribble condition detected
>      670450255 packets output, 115399962776 bytes, 0 underruns
>      0 output errors, 0 collisions, 1 interface resets
>      0 babbles, 0 late collision, 0 deferred
>      0 lost carrier, 0 no carrier, 0 PAUSE output
>      0 output buffer failures, 0 output buffers swapped out
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