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194125e3eb
This applies to both user-mode and !user-mode emulation.
Instead of relying on a global lock, protect the list of incoming
jumps with tb->jmp_lock. This lock also protects tb->cflags,
so update all tb->cflags readers outside tb->jmp_lock to use
atomic reads via tb_cflags().
In order to find the destination TB (and therefore its jmp_lock)
from the origin TB, we introduce tb->jmp_dest[].
I considered not using a linked list of jumps, which simplifies
code and makes the struct smaller. However, it unnecessarily increases
memory usage, which results in a performance decrease. See for
instance these numbers booting+shutting down debian-arm:
Time (s) Rel. err (%) Abs. err (s) Rel. slowdown (%)
------------------------------------------------------------------------------
before 20.88 0.74 0.154512 0.
after 20.81 0.38 0.079078 -0.33524904
GTree 21.02 0.28 0.058856 0.67049808
GHashTable + xxhash 21.63 1.08 0.233604 3.5919540
Using a hash table or a binary tree to keep track of the jumps
doesn't really pay off, not only due to the increased memory usage,
but also because most TBs have only 0 or 1 jumps to them. The maximum
number of jumps when booting debian-arm that I measured is 35, but
as we can see in the histogram below a TB with that many incoming jumps
is extremely rare; the average TB has 0.80 incoming jumps.
n_jumps: 379208; avg jumps/tb: 0.801099
dist: [0.0,1.0)|▄█▁▁▁▁▁▁▁▁▁▁▁ ▁▁▁▁▁▁ ▁▁▁ ▁▁▁ ▁|[34.0,35.0]
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
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| .. | ||
| user | ||
| address-spaces.h | ||
| cpu-all.h | ||
| cpu-common.h | ||
| cpu-defs.h | ||
| cpu_ldst.h | ||
| cpu_ldst_template.h | ||
| cpu_ldst_useronly_template.h | ||
| cputlb.h | ||
| exec-all.h | ||
| gdbstub.h | ||
| gen-icount.h | ||
| helper-gen.h | ||
| helper-head.h | ||
| helper-proto.h | ||
| helper-tcg.h | ||
| hwaddr.h | ||
| ioport.h | ||
| log.h | ||
| memattrs.h | ||
| memory-internal.h | ||
| memory.h | ||
| memory_ldst.inc.h | ||
| memory_ldst_cached.inc.h | ||
| memory_ldst_phys.inc.h | ||
| poison.h | ||
| ram_addr.h | ||
| ramlist.h | ||
| semihost.h | ||
| softmmu-semi.h | ||
| target_page.h | ||
| tb-context.h | ||
| tb-hash-xx.h | ||
| tb-hash.h | ||
| tb-lookup.h | ||
| translator.h | ||