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High memory I/O util in RSP720-3C-GE

Hi,

I have 7609-S chassis with RSP720-3C-GE installed as PE router. DRAM installed is about 1GB. Few days ago I noticed that the I/O memory usage is considerably high which is about 68-70%. At first, I consider it as having memory leak bug CSCtr34960 that I previously raised to TAC with my SUP720-3BXL supervisor. The solution for CSCtr34960 with SUP720-3BXL is IOS upgrade.

With the TAC information for memory leak in SUP720-3BXL, I tried to also upgrade the IOS of RSP720-3C-GE.

Before upgrade: RSP720-3C-GE with SRE4

After upgrade: RSP720-3C-GE with 15.2(2)S

Directly after upgrade, I noticed that the I/O memory usage is still considerably high and increasing about 1-2% compared with before upgrading. Here is the output:

cs-belanti.1#sh mem stat

                Head    Total(b)     Used(b)     Free(b)   Lowest(b)  Largest(b)

Processor   13C862C4   674733372   253148764   421584608   420232456   421147972

      I/O   3C000000    67108864    46746960    20361904    20361904    20347964

I checked into my other devices with SUP720-3B, SUP-720-3BXL, and RSP-720-3C-GE I/O memory status and found that all RSPs are having I/O memory utilization above 60%. SUP720-3B and 3BXL only use about 25% of I/O memory. I have about 20 RSPs and about 50SUPs so I think the sample would be enough to determine that all RSPs consume very large I/O memory.

I have make sure that CPU is still underutilized (<10%) and having no buffer issue:

cs-belanti.1# sh buffers

Buffer elements:

     855 in free list

     29037294 hits, 0 misses, 617 created

Public buffer pools:

Small buffers, 104 bytes (total 1024, permanent 1024):

     1017 in free list (128 min, 2048 max allowed)

     13181038 hits, 0 misses, 0 trims, 0 created

     0 failures (0 no memory)

Medium buffers, 256 bytes (total 3000, permanent 3000):

     3000 in free list (64 min, 3000 max allowed)

     271142 hits, 0 misses, 0 trims, 0 created

     0 failures (0 no memory)

Middle buffers, 600 bytes (total 512, permanent 512):

     511 in free list (64 min, 1024 max allowed)

     65503 hits, 0 misses, 0 trims, 0 created

     0 failures (0 no memory)

Big buffers, 1536 bytes (total 1000, permanent 1000):

     1000 in free list (64 min, 1000 max allowed)

     1169354 hits, 0 misses, 0 trims, 0 created

     0 failures (0 no memory)

VeryBig buffers, 4520 bytes (total 10, permanent 10, peak 23 @ 16:10:46):

     9 in free list (0 min, 300 max allowed)

     25067 hits, 7 misses, 13 trims, 13 created

     1 failures (0 no memory)

Large buffers, 9240 bytes (total 8, permanent 8, peak 12 @ 14:48:33):

     8 in free list (0 min, 10 max allowed)

     136252 hits, 2 misses, 4 trims, 4 created

     0 failures (0 no memory)

Huge buffers, 18024 bytes (total 2, permanent 2):

     2 in free list (0 min, 4 max allowed)

     0 hits, 0 misses, 0 trims, 0 created

     0 failures (0 no memory)

Can anyone help me in this case? Is I/O memory usage above 60% in an underutilized 7600 router with RSP normal?

It seems that we cannot manually determine the size of I/O memory in 7600 since the value given should be the best practice.

Thanks,

Sincerely,

Jeffry

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