Deciding To Tune Buffers - Dell S4048–ON Configuration Manual

• Dynamic buffer — this pool is shared memory that is allocated as needed, up to a configured limit. Using dynamic buffers
provides the benefit of statistical buffer sharing. An interface requests dynamic buffers when its dedicated buffer pool is
exhausted. The buffer manager grants the request based on three conditions:
– The number of used and available dynamic buffers.
– The maximum number of cells that an interface can occupy.
– Available packet pointers (2k per interface). Each packet is managed in the buffer using a unique packet pointer. Thus, each
interface can manage up to 2k packets.
You can configure dynamic buffers per port on both 1G and 10G FPs and per queue on CSFs. By default, the FP dynamic buffer
allocation is 10 times oversubscribed. For the 48-port 1G card:
• Dynamic Pool= Total Available Pool(16384 cells) — Total Dedicated Pool = 5904 cells
• Oversubscription ratio = 10
• Dynamic Cell Limit Per port = 59040/29 = 2036 cells
Figure 163. Buffer Tuning Points

Deciding to Tune Buffers

Dell Networking recommends exercising caution when configuring any non-default buffer settings, as tuning can significantly affect
system performance. The default values work for most cases.
As a guideline, consider tuning buffers if traffic is bursty (and coming from several interfaces). In this case:
• Reduce the dedicated buffer on all queues/interfaces.
• Increase the dynamic buffer on all interfaces.
• Increase the cell pointers on a queue that you are expecting will receive the largest number of packets.
To define, change, and apply buffers, use the following commands.
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Debugging and Diagnostics