LL perf (Textures/assets): `LLFileSystem` reopens the file for every operation #301

New issue

Closed

opened 2026-10-04 14:09:14 +00:00 by sky_line · 0 comments

sky_line commented

2026-10-04 14:09:14 +00:00

Owner

From the LL-origin inefficiency audit (finding T5). File/line references are from commit 0229f8872c; re-locate them before working.

LLFileSystem reopens the file for every operation

Where: llfilesystem/llfilesystem.cpp.
- The constructor does fileExists plus a last_write_time stat, and possibly utime (:57-71, 300-359).
- getSize() opens an ifstream and seeks to the end (:122-135); seek() and eof() both call getSize() (:176-179, 247).
- read/write open and close a stream each time (:137-236).
- getExists() opens an ifstream and seeks to test for non-zero size (:74-87).
Where it hurts:
- A mesh LOD cache hit costs ~4 opens plus 2 stats (llmeshrepository.cpp:2046-2080).
- Vorbis decode calls read per chunk plus getSize per SEEK_END (llaudiodecodemgr.cpp:100-160).
- 39k mesh fetches at login.
Fix: open once and hold the fd; fstat once; pread; one utimensat only when stale.
Confirmed. S-M.

Verify the cost (profile or timer) before and after changing it.

From the LL-origin inefficiency audit (finding T5). File/line references are from commit 0229f8872c; re-locate them before working. **`LLFileSystem` reopens the file for every operation** - **Where:** `llfilesystem/llfilesystem.cpp`. - The constructor does `fileExists` plus a `last_write_time` stat, and possibly `utime` (`:57-71, 300-359`). - `getSize()` opens an ifstream and seeks to the end (`:122-135`); `seek()` and `eof()` both call `getSize()` (`:176-179, 247`). - `read`/`write` open and close a stream each time (`:137-236`). - `getExists()` opens an ifstream and seeks to test for non-zero size (`:74-87`). - **Where it hurts:** - A mesh LOD cache hit costs ~4 opens plus 2 stats (`llmeshrepository.cpp:2046-2080`). - Vorbis decode calls `read` per chunk plus `getSize` per SEEK_END (`llaudiodecodemgr.cpp:100-160`). - 39k mesh fetches at login. - **Fix:** open once and hold the fd; `fstat` once; `pread`; one `utimensat` only when stale. - Confirmed. S-M. Verify the cost (profile or timer) before and after changing it.

sky_line added the

perf

label

2026-10-04 14:09:14 +00:00

sky_line added this to the Slipstream project

2026-10-06 15:04:13 +00:00

sky_line added the

status

in-progress

label

2026-10-08 02:07:16 +00:00

sky_line referenced this issue from a commit