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author | kib <kib@FreeBSD.org> | 2012-03-10 08:49:44 +0000 |
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committer | kib <kib@FreeBSD.org> | 2012-03-10 08:49:44 +0000 |
commit | fb48ba5d907bec4322e4292fd840d33a0bb662ac (patch) | |
tree | a8f58ba276201ae6ec5ed36f99021f82c9135db4 /libexec/rtld-elf | |
parent | b186de9a2407a944cc309e501c75e8e9afe37ab5 (diff) | |
download | FreeBSD-src-fb48ba5d907bec4322e4292fd840d33a0bb662ac.zip FreeBSD-src-fb48ba5d907bec4322e4292fd840d33a0bb662ac.tar.gz |
Optimize tls_get_addr_common(). The change provides around 30% speedup
for TLS microbenchmark using global-dynamic TLS model on amd64 (which is
default for PIC dso objects).
Split the slow path into tls_get_addr_slow(), for which inlining is
disabled. This prevents the registers spill on tls_get_addr_common()
entry.
Provide static branch hint to the compiler, indicating that slow path
is not likely to be taken.
While there, do some minimal style adjustments.
Reported and tested by: davidxu
MFC after: 1 week
Diffstat (limited to 'libexec/rtld-elf')
-rw-r--r-- | libexec/rtld-elf/rtld.c | 31 |
1 files changed, 22 insertions, 9 deletions
diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c index 568d10b..b8524da 100644 --- a/libexec/rtld-elf/rtld.c +++ b/libexec/rtld-elf/rtld.c @@ -3507,17 +3507,17 @@ unref_dag(Obj_Entry *root) /* * Common code for MD __tls_get_addr(). */ -void * -tls_get_addr_common(Elf_Addr** dtvp, int index, size_t offset) +static void *tls_get_addr_slow(Elf_Addr **, int, size_t) __noinline; +static void * +tls_get_addr_slow(Elf_Addr **dtvp, int index, size_t offset) { - Elf_Addr* dtv = *dtvp; + Elf_Addr *newdtv, *dtv; RtldLockState lockstate; + int to_copy; + dtv = *dtvp; /* Check dtv generation in case new modules have arrived */ if (dtv[0] != tls_dtv_generation) { - Elf_Addr* newdtv; - int to_copy; - wlock_acquire(rtld_bind_lock, &lockstate); newdtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr)); to_copy = dtv[1]; @@ -3532,14 +3532,27 @@ tls_get_addr_common(Elf_Addr** dtvp, int index, size_t offset) } /* Dynamically allocate module TLS if necessary */ - if (!dtv[index + 1]) { + if (dtv[index + 1] == 0) { /* Signal safe, wlock will block out signals. */ - wlock_acquire(rtld_bind_lock, &lockstate); + wlock_acquire(rtld_bind_lock, &lockstate); if (!dtv[index + 1]) dtv[index + 1] = (Elf_Addr)allocate_module_tls(index); lock_release(rtld_bind_lock, &lockstate); } - return (void*) (dtv[index + 1] + offset); + return ((void *)(dtv[index + 1] + offset)); +} + +void * +tls_get_addr_common(Elf_Addr **dtvp, int index, size_t offset) +{ + Elf_Addr *dtv; + + dtv = *dtvp; + /* Check dtv generation in case new modules have arrived */ + if (__predict_true(dtv[0] == tls_dtv_generation && + dtv[index + 1] != 0)) + return ((void *)(dtv[index + 1] + offset)); + return (tls_get_addr_slow(dtvp, index, offset)); } #if defined(__arm__) || defined(__ia64__) || defined(__mips__) || defined(__powerpc__) |