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tcg: Tidy tcg_n_regions 

Compute the value using straight division and bounds,
rather than a loop.  Pass in tb_size rather than reading
from tcg_init_ctx.code_gen_buffer_size,

Reviewed-by: Luis Pires <luis.pires@eldorado.org.br>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2021-03-10 11:06:17 -06:00
parent c2471ca0de
commit 01afda9919
1 changed files with 12 additions and 17 deletions
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29
tcg/region.c
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@ -364,38 +364,33 @@ void tcg_region_reset_all(void)
tcg_region_tree_reset_all();
}
static size_t tcg_n_regions(unsigned max_cpus)
static size_t tcg_n_regions(size_t tb_size, unsigned max_cpus)
{
#ifdef CONFIG_USER_ONLY
return 1;
#else
size_t n_regions;
/*
* It is likely that some vCPUs will translate more code than others,
* so we first try to set more regions than max_cpus, with those regions
* being of reasonable size. If that's not possible we make do by evenly
* dividing the code_gen_buffer among the vCPUs.
*/
size_t i;
/* Use a single region if all we have is one vCPU thread */
if (max_cpus == 1 || !qemu_tcg_mttcg_enabled()) {
return 1;
}
/* Try to have more regions than max_cpus, with each region being >= 2 MB */
for (i = 8; i > 0; i--) {
size_t regions_per_thread = i;
size_t region_size;
region_size = tcg_init_ctx.code_gen_buffer_size;
region_size /= max_cpus * regions_per_thread;
if (region_size >= 2 * 1024u * 1024) {
return max_cpus * regions_per_thread;
}
/*
* Try to have more regions than max_cpus, with each region being >= 2 MB.
* If we can't, then just allocate one region per vCPU thread.
*/
n_regions = tb_size / (2 * MiB);
if (n_regions <= max_cpus) {
return max_cpus;
}
/* If we can't, then just allocate one region per vCPU thread */
return max_cpus;
return MIN(n_regions, max_cpus * 8);
#endif
}
@ -833,7 +828,7 @@ void tcg_region_init(size_t tb_size, int splitwx, unsigned max_cpus)
buf = tcg_init_ctx.code_gen_buffer;
total_size = tcg_init_ctx.code_gen_buffer_size;
page_size = qemu_real_host_page_size;
n_regions = tcg_n_regions(max_cpus);
n_regions = tcg_n_regions(total_size, max_cpus);
/* The first region will be 'aligned - buf' bytes larger than the others */
aligned = QEMU_ALIGN_PTR_UP(buf, page_size);