### Improve expired commands performance with IO threads
#### Background
In our IO threads architecture, IO threads allocate client argv's and
later when we free it after processCommand we offload its free to the IO
threads.
With jemalloc, it's crucial that the same thread that allocates memory
also frees it.
For some commands we modify the client's argv in the main thread during
command processing (for example in `SET EX` command we rewrite the
command to use absolute time for replication propagation).
#### Current issues
1. When commands are rewritten (e.g., expire commands), we store the
original argv
in `c->original_argv`. However, we're currently:
- Freeing new argv (allocated by main thread) in IO threads
- Freeing original argv (allocated by IO threads) in main thread
2. Currently, `c->original_argv` points to new array with old
objects, while `c->argv` has old array with new objects, making memory
free management complicated.
#### Changes
1. Refactored argv modification handling code to ensure consistency -
both array and objects are now either all new or all old
2. Moved original_argv cleanup to happen in resetClient after argv
cleanup
3. Modified IO threads code to properly handle original argv cleanup
when argv are modified.
#### Performance Impact
Benchmark with `SET EX` commands (650 clients, 512 byte value, 8 IO
threads):
- New implementation: **729,548 ops/sec**
- Old implementation: **633,243 ops/sec**
Representing a **~15%** performance improvement due to more efficient
memory handling.
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Signed-off-by: Uri Yagelnik <uriy@amazon.com>
Signed-off-by: ranshid <88133677+ranshid@users.noreply.github.com>
Co-authored-by: ranshid <88133677+ranshid@users.noreply.github.com>
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