Messages in this thread Patch in this message |  | | Date | Fri, 05 Oct 2001 17:04:21 +0530 | From | "BALBIR SINGH" <> | Subject | [RFC][PATCH]Small Minor optimization to kmem_cache_estimate |
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A small minor optimization in kmem_cache_estimate() slab.c
The patch below saves some CPU cycles, especially when the value of size is small. This is against 2.4.2-2.
--- slab.c.org Fri Oct 5 16:09:39 2001 +++ slab.c Fri Oct 5 16:46:34 2001 @@ -386,10 +386,10 @@ base = sizeof(slab_t); extra = sizeof(kmem_bufctl_t); } - i = 0; + i = (wastage - base)/(size + extra); while (i*size + L1_CACHE_ALIGN(base+i*extra) <= wastage) i++; - if (i > 0) + while (i*size + L1_CACHE_ALIGN(base+i*extra) > wastage) i--;
instead of looping through to get the right value, we make a guess (mathematically) and move a bit to get the correct value.
Hey, I remember reading the Newton-Raphson method in school. I verified the number of objects per slab is the same in both cases. This patch may not improve the performance of your CPU by a great amount, but when there is a faster way to do things, why live with the slower one.
NOTE: The code hardly does one loop in both the while statements.
Comments, Balbir
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