issue: #41435
After introducing the caching layer's lazy loading and eviction
mechanisms, most parts of a segment won't be loaded into memory or disk
immediately, even if the segment is marked as LOADED. This means
physical resource usage may be very low. However, we still need to
reserve enough resources for the segments marked as LOADED. Thus, the
logic of resource usage estimation during segment loading, which based
on physcial resource usage only for now, should be changed.
To address this issue, we introduced the concept of logical resource
usage in this patch. This can be thought of as the base reserved
resource for each LOADED segment.
A segment’s logical resource usage is derived from its final evictable
and inevictable resource usage and calculated as follows:
```
SLR = SFPIER + evitable_cache_ratio * SFPER
```
it also equals to
```
SLR = (SFPIER + SFPER) - (1.0 - evitable_cache_ratio) * SFPER
```
`SLR`: The logical resource usage of a segment.
`SFPIER`: The final physical inevictable resource usage of a segment.
`SFPER`: The final physical evictable resource usage of a segment.
`evitable_cache_ratio`: The ratio of a segment's evictable resources
that can be cached locally. The higher the ratio, the more physical
memory is reserved for evictable memory.
When loading a segment, two types of resource usage are taken into
account.
First is the estimated maximum physical resource usage:
```
PPR = HPR + CPR + SMPR - SFPER
```
`PPR`: The predicted physical resource usage after the current segment
is allowed to load.
`HPR`: The physical resource usage obtained from hardware information.
`CPR`: The total physical resource usage of segments that have been
committed but not yet loaded. When one new segment is allow to load,
`CPR' = CPR + (SMR - SER)`. When one of the committed segments is
loaded, `CPR' = CPR - (SMR - SER)`.
`SMPR`: The maximum physical resource usage of the current segment.
`SFPER`: The final physical evictable resource usage of the current
segment.
Second is the estimated logical resource usage, this check is only valid
when eviction is enabled:
```
PLR = LLR + CLR + SLR
```
`PLR`: The predicted logical resource usage after the current segment is
allowed to load.
`LLR`: The total logical resource usage of all loaded segments. When a
new segment is loaded, `LLR` should be updated to `LLR' = LLR + SLR`.
`CLR`: The total logical resource usage of segments that have been
committed but not yet loaded. When one new segment is allow to load,
`CLR' = CLR + SLR`. When one of the committed segments is loaded, `CLR'
= CLR - SLR`.
`SLR`: The logical resource usage of the current segment.
Only when `PPR < PRL && PLR < PRL` (`PRL`: Physical resource limit of
the querynode), the segment is allowed to be loaded.
---------
Signed-off-by: Shawn Wang <shawn.wang@zilliz.com>
