chore(gpu): fix mul throughput benchmark

tfhe-benchmark/src/utilities.rs

@@ -394,9 +394,11 @@ pub fn throughput_num_threads(num_block: usize, op_pbs_count: u64) -> u64 {
 
     #[cfg(feature = "gpu")]
     {
+        let safety_factor = 0.9f64; // Avoid OOM error in mul bench
         let total_num_sm = H100_PCIE_SM_COUNT * get_number_of_gpus();
         let operation_loading = ((total_num_sm as u64 / op_pbs_count) as f64).max(minimum_loading);
-        let elements = (total_num_sm as f64 * block_multiplicator * operation_loading) as u64;
+        let elements =
+            (total_num_sm as f64 * block_multiplicator * operation_loading * safety_factor) as u64;
         elements.min(1500) // This threshold is useful for operation with both a small number of
                            // block and low PBs count.
     }