Memory Allocation Strategy - Problems

Consider the requests from processes in given order 300K, 25K, 125K, and 50K. Let there be two blocks of memory available of size 150K followed by a block size 350K. Which of the memory allocation schemes can satisfy the above requests? Justify your answer. ( univeristy question)

Given:

• Memory blocks:
  • Block 1 = 150K
  • Block 2 = 350K
• Process requests (in order):
  • 300K → 25K → 125K → 50K

---

1️⃣ First Fit

Allocate each process to the first block large enough.

Step-by-step:

• 300K → fits in 350K → remaining = 50K
• 25K → fits in 150K → remaining = 125K
• 125K → fits in remaining 125K → remaining = 0
• 50K → fits in remaining 50K → remaining = 0

✅ All processes allocated successfully

---

2️⃣ Best Fit

Allocate each process to the smallest sufficient block.

Step-by-step:

• 300K → fits only in 350K → remaining = 50K
• 25K → fits in 50K (better than 150K) → remaining = 25K
• 125K → fits in 150K → remaining = 25K
• 50K → ❌ cannot fit (only 25K + 25K left, not contiguous)

❌ Fails to allocate all processes

---

3️⃣ Worst Fit

Allocate each process to the largest available block.

Step-by-step:

• 300K → allocated to 350K → remaining = 50K
• 25K → allocated to 150K → remaining = 125K
• 125K → allocated to 125K → remaining = 0
• 50K → allocated to 50K → remaining = 0

✅ All processes allocated successfully

---

Final Answer:

Allocation Scheme	Can satisfy all requests?
First Fit	✅ Yes
Best Fit	❌ No
Worst Fit	✅ Yes

---

Justification:

• Best Fit fails due to fragmentation—it leaves small unusable gaps.
• First Fit and Worst Fit succeed because they leave usable block sizes for later processes.