Difference between revisions of "Porting/LLVMpipe"
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[https://docs.mesa3d.org/drivers/llvmpipe.html LLVMpipe] is [https://gitlab.freedesktop.org/mesa/mesa/-/blob/19682028eb0a2143c18ab2a26f3b23b7f74b2335/src/gallium/drivers/llvmpipe/lp_limits.h#L69 limited to 16 threads]. The only easily findable justification for this limit is in [https://gitlab.freedesktop.org/mesa/mesa/-/commit/38a751cbe85b7e31925931dc4994e7def5e5af96 a commit from 2013], where it was increased from 8 because a user reported on a mailing list that 16 was faster for them. Given that POWER9 systems often have much higher thread counts than this, this limit may be suboptimal for POWER9. | [https://docs.mesa3d.org/drivers/llvmpipe.html LLVMpipe] is [https://gitlab.freedesktop.org/mesa/mesa/-/blob/19682028eb0a2143c18ab2a26f3b23b7f74b2335/src/gallium/drivers/llvmpipe/lp_limits.h#L69 limited to 16 threads]. The only easily findable justification for this limit is in [https://gitlab.freedesktop.org/mesa/mesa/-/commit/38a751cbe85b7e31925931dc4994e7def5e5af96 a commit from 2013], where it was increased from 8 because a user reported on a mailing list that 16 was faster for them. Given that POWER9 systems often have much higher thread counts than this, this limit may be suboptimal for POWER9. | ||
| − | [[User:Luke-jr|luke-jr]] anecdotally reports that bumping the limit to 128 threads noticeably improved performance in 3D games, e.g. Jedi Academy became playable. However, it also had the side effect that most GUI applications spawned 128 LLVMpipe threads, which was annoying in <code>gdb</code>/<code>top</code>. Luke's patch is: | + | [[User:Luke-jr|luke-jr]] anecdotally reports that bumping the limit to 128 threads noticeably improved performance in 3D games, e.g. Jedi Academy became playable. However, it also had the side effect that most GUI applications spawned 128 LLVMpipe threads, which was annoying in <code>gdb</code>/<code>top</code>. Luke worked around this issue by setting the environment variable <code>LP_NUM_THREADS=2</code> globally, and overriding for 3D applications that needed more threads. Luke's patch is: |
diff -ur mesa-17.3.9.orig/src/gallium/drivers/llvmpipe/lp_limits.h mesa-17.3.9/src/gallium/drivers/llvmpipe/lp_limits.h | diff -ur mesa-17.3.9.orig/src/gallium/drivers/llvmpipe/lp_limits.h mesa-17.3.9/src/gallium/drivers/llvmpipe/lp_limits.h | ||
Revision as of 09:51, 10 June 2022
Thread Count
LLVMpipe is limited to 16 threads. The only easily findable justification for this limit is in a commit from 2013, where it was increased from 8 because a user reported on a mailing list that 16 was faster for them. Given that POWER9 systems often have much higher thread counts than this, this limit may be suboptimal for POWER9.
luke-jr anecdotally reports that bumping the limit to 128 threads noticeably improved performance in 3D games, e.g. Jedi Academy became playable. However, it also had the side effect that most GUI applications spawned 128 LLVMpipe threads, which was annoying in gdb/top. Luke worked around this issue by setting the environment variable LP_NUM_THREADS=2 globally, and overriding for 3D applications that needed more threads. Luke's patch is:
diff -ur mesa-17.3.9.orig/src/gallium/drivers/llvmpipe/lp_limits.h mesa-17.3.9/src/gallium/drivers/llvmpipe/lp_limits.h --- mesa-17.3.9.orig/src/gallium/drivers/llvmpipe/lp_limits.h 2018-04-18 04:44:00.000000000 -0400 +++ mesa-17.3.9/src/gallium/drivers/llvmpipe/lp_limits.h 2018-05-02 05:20:57.586000000 -0400 @@ -61,7 +61,7 @@ #define LP_MAX_WIDTH (1 << (LP_MAX_TEXTURE_LEVELS - 1)) -#define LP_MAX_THREADS 16 +#define LP_MAX_THREADS 128 /** Only in mesa-17.3.9/src/gallium/drivers/llvmpipe: lp_limits.h~
