[bugfix](cache) the cache capacity is wrong when memusage > soft meml…

…imit (apache#40961)

## Proposed changes

bug is introduced by apache#40542

Co-authored-by: yiguolei <[email protected]>

be/src/common/daemon.cpp

@@ -245,10 +245,14 @@ void refresh_cache_capacity() {
         auto cache_capacity_reduce_mem_limit = uint64_t(
                 doris::MemInfo::soft_mem_limit() * config::cache_capacity_reduce_mem_limit_frac);
         int64_t process_memory_usage = doris::GlobalMemoryArbitrator::process_memory_usage();
+        // the rule is like this:
+        // 1. if the process mem usage < soft memlimit * 0.6, then do not need adjust cache capacity.
+        // 2. if the process mem usage > soft memlimit * 0.6 and process mem usage < soft memlimit, then it will be adjusted to a lower value.
+        // 3. if the process mem usage > soft memlimit, then the capacity is adjusted to 0.
         double new_cache_capacity_adjust_weighted =
                 process_memory_usage <= cache_capacity_reduce_mem_limit
                         ? 1
-                        : std::min<double>(
+                        : std::max<double>(
                                   1 - (process_memory_usage - cache_capacity_reduce_mem_limit) /
                                                   (doris::MemInfo::soft_mem_limit() -
                                                    cache_capacity_reduce_mem_limit),