| Message ID | 577EB19A.8040206@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/07/16 22:46, Sergey Fedorov wrote: > On 07/07/16 22:36, Alex Bennée wrote: >> Sergey Fedorov <sergey.fedorov@linaro.org> writes: >> >>> From: Sergey Fedorov <serge.fdrv@gmail.com> >>> >>> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> >>> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> >>> --- >>> cpu-exec.c | 15 +++++++++------ >>> 1 file changed, 9 insertions(+), 6 deletions(-) >>> >>> diff --git a/cpu-exec.c b/cpu-exec.c >>> index dd0bd5007701..54c935039592 100644 >>> --- a/cpu-exec.c >>> +++ b/cpu-exec.c >>> @@ -295,7 +295,8 @@ static TranslationBlock *tb_find_slow(CPUState *cpu, >>> >>> /* mmap_lock is needed by tb_gen_code, and mmap_lock must be >>> * taken outside tb_lock. As system emulation is currently >>> - * single threaded the locks are NOPs. >>> + * single threaded the locks are NOPs. Both locks are to be >>> + * released at the end of tb_find_fast(). >>> */ >>> mmap_lock(); >>> tb_lock(); >>> @@ -308,9 +309,6 @@ static TranslationBlock *tb_find_slow(CPUState *cpu, >>> /* if no translated code available, then translate it now */ >>> tb = tb_gen_code(cpu, pc, cs_base, flags, 0); >>> } >>> - >>> - tb_unlock(); >>> - mmap_unlock(); >> Hmm pushing these outside of tb_find_slow() makes me uncomfortable. I >> guess tb_find_fast/slow are intimately tied together but the idea of >> taking locks which are the responsibility of the calling function to >> clear seems ugly to me. > Okay, what if we also: > > diff --git a/cpu-exec.c b/cpu-exec.c > index 54c935039592..ff8f92bc1dc1 100644 > --- a/cpu-exec.c > +++ b/cpu-exec.c > @@ -278,45 +278,7 @@ static TranslationBlock *tb_find_physical(CPUState > *cpu, > return qht_lookup(&tcg_ctx.tb_ctx.htable, tb_cmp, &desc, h); > } > > -static TranslationBlock *tb_find_slow(CPUState *cpu, > - target_ulong pc, > - target_ulong cs_base, > - uint32_t flags) > -{ > - TranslationBlock *tb; > - > - /* Ensure that we won't find a TB in the shared hash table > - * if it is being invalidated by some other thread. > - * Otherwise we'd put it back to CPU's local cache. > - * Pairs with smp_wmb() in tb_phys_invalidate(). */ > - smp_rmb(); > - tb = tb_find_physical(cpu, pc, cs_base, flags); > - if (!tb) { > - > - /* mmap_lock is needed by tb_gen_code, and mmap_lock must be > - * taken outside tb_lock. As system emulation is currently > - * single threaded the locks are NOPs. Both locks are to be > - * released at the end of tb_find_fast(). > - */ > - mmap_lock(); > - tb_lock(); > - > - /* There's a chance that our desired tb has been translated while > - * taking the locks so we check again inside the lock. > - */ > - tb = tb_find_physical(cpu, pc, cs_base, flags); > - if (!tb) { > - /* if no translated code available, then translate it now */ > - tb = tb_gen_code(cpu, pc, cs_base, flags, 0); > - } > - } > - > - /* We add the TB in the virtual pc hash table for the fast lookup */ > - atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb); > - return tb; > -} > - > -static inline TranslationBlock *tb_find_fast(CPUState *cpu, > +static inline TranslationBlock *tb_find(CPUState *cpu, > TranslationBlock **last_tb, > int tb_exit) > { > @@ -332,7 +294,34 @@ static inline TranslationBlock > *tb_find_fast(CPUState *cpu, > tb = atomic_read(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)]); > if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base || > tb->flags != flags)) { > - tb = tb_find_slow(cpu, pc, cs_base, flags); > + /* Ensure that we won't find a TB in the shared hash table > + * if it is being invalidated by some other thread. > + * Otherwise we'd put it back to CPU's local cache. > + * Pairs with smp_wmb() in tb_phys_invalidate(). */ > + smp_rmb(); > + tb = tb_find_physical(cpu, pc, cs_base, flags); > + if (!tb) { > + > + /* mmap_lock is needed by tb_gen_code, and mmap_lock must be > + * taken outside tb_lock. As system emulation is currently > + * single threaded the locks are NOPs. Both locks are to be > + * released at the end of the function. > + */ > + mmap_lock(); > + tb_lock(); > + > + /* There's a chance that our desired tb has been translated > while > + * taking the locks so we check again inside the lock. > + */ > + tb = tb_find_physical(cpu, pc, cs_base, flags); > + if (!tb) { > + /* if no translated code available, then translate it > now */ > + tb = tb_gen_code(cpu, pc, cs_base, flags, 0); > + } > + } > + > + /* We add the TB in the virtual pc hash table for the fast > lookup */ > + atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb); > } > if (cpu->tb_flushed) { > /* Ensure that no TB jump will be modified as the > @@ -440,7 +429,7 @@ static inline bool cpu_handle_exception(CPUState > *cpu, int *ret) > && cpu->icount_decr.u16.low + cpu->icount_extra == 0) { > /* try to cause an exception pending in the log */ > TranslationBlock *last_tb = NULL; /* Avoid chaining TBs */ > - cpu_exec_nocache(cpu, 1, tb_find_fast(cpu, &last_tb, 0), true); > + cpu_exec_nocache(cpu, 1, tb_find(cpu, &last_tb, 0), true); > *ret = -1; > return true; > #endif > @@ -624,7 +613,7 @@ int cpu_exec(CPUState *cpu) > cpu->tb_flushed = false; /* reset before first TB lookup */ > for(;;) { > cpu_handle_interrupt(cpu, &last_tb); > - tb = tb_find_fast(cpu, &last_tb, tb_exit); > + tb = tb_find(cpu, &last_tb, tb_exit); > cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit, &sc); > /* Try to align the host and virtual clocks > if the guest is in advance */ > > Using goto statements, the lines from tb_find_slow() which take the locks can even be on the same indentation level as the lines resetting them. I could prepare a patch series based on your first 3 patches and this idea. Regards, Sergey > > >>> } >>> >>> /* We add the TB in the virtual pc hash table for the fast lookup */ >>> @@ -354,10 +352,15 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, >>> #endif >>> /* See if we can patch the calling TB. */ >>> if (*last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) { >>> - tb_lock(); >>> + if (!tb_lock_locked()) { >>> + tb_lock(); >>> + } >>> tb_add_jump(*last_tb, tb_exit, tb); >>> - tb_unlock(); >>> } >>> + >>> + tb_lock_reset(); >>> + mmap_lock_reset(); >>> + >>> return tb; >>> } >> -- >> Alex Bennée
Sergey Fedorov <serge.fdrv@gmail.com> writes: > On 07/07/16 22:46, Sergey Fedorov wrote: >> On 07/07/16 22:36, Alex Bennée wrote: >>> Sergey Fedorov <sergey.fedorov@linaro.org> writes: >>> >>>> From: Sergey Fedorov <serge.fdrv@gmail.com> >>>> >>>> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com> >>>> Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org> >>>> --- >>>> cpu-exec.c | 15 +++++++++------ >>>> 1 file changed, 9 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/cpu-exec.c b/cpu-exec.c >>>> index dd0bd5007701..54c935039592 100644 >>>> --- a/cpu-exec.c >>>> +++ b/cpu-exec.c >>>> @@ -295,7 +295,8 @@ static TranslationBlock *tb_find_slow(CPUState *cpu, >>>> >>>> /* mmap_lock is needed by tb_gen_code, and mmap_lock must be >>>> * taken outside tb_lock. As system emulation is currently >>>> - * single threaded the locks are NOPs. >>>> + * single threaded the locks are NOPs. Both locks are to be >>>> + * released at the end of tb_find_fast(). >>>> */ >>>> mmap_lock(); >>>> tb_lock(); >>>> @@ -308,9 +309,6 @@ static TranslationBlock *tb_find_slow(CPUState *cpu, >>>> /* if no translated code available, then translate it now */ >>>> tb = tb_gen_code(cpu, pc, cs_base, flags, 0); >>>> } >>>> - >>>> - tb_unlock(); >>>> - mmap_unlock(); >>> Hmm pushing these outside of tb_find_slow() makes me uncomfortable. I >>> guess tb_find_fast/slow are intimately tied together but the idea of >>> taking locks which are the responsibility of the calling function to >>> clear seems ugly to me. >> Okay, what if we also: >> >> diff --git a/cpu-exec.c b/cpu-exec.c >> index 54c935039592..ff8f92bc1dc1 100644 >> --- a/cpu-exec.c >> +++ b/cpu-exec.c >> @@ -278,45 +278,7 @@ static TranslationBlock *tb_find_physical(CPUState >> *cpu, >> return qht_lookup(&tcg_ctx.tb_ctx.htable, tb_cmp, &desc, h); >> } >> >> -static TranslationBlock *tb_find_slow(CPUState *cpu, >> - target_ulong pc, >> - target_ulong cs_base, >> - uint32_t flags) >> -{ >> - TranslationBlock *tb; >> - >> - /* Ensure that we won't find a TB in the shared hash table >> - * if it is being invalidated by some other thread. >> - * Otherwise we'd put it back to CPU's local cache. >> - * Pairs with smp_wmb() in tb_phys_invalidate(). */ >> - smp_rmb(); >> - tb = tb_find_physical(cpu, pc, cs_base, flags); >> - if (!tb) { >> - >> - /* mmap_lock is needed by tb_gen_code, and mmap_lock must be >> - * taken outside tb_lock. As system emulation is currently >> - * single threaded the locks are NOPs. Both locks are to be >> - * released at the end of tb_find_fast(). >> - */ >> - mmap_lock(); >> - tb_lock(); >> - >> - /* There's a chance that our desired tb has been translated while >> - * taking the locks so we check again inside the lock. >> - */ >> - tb = tb_find_physical(cpu, pc, cs_base, flags); >> - if (!tb) { >> - /* if no translated code available, then translate it now */ >> - tb = tb_gen_code(cpu, pc, cs_base, flags, 0); >> - } >> - } >> - >> - /* We add the TB in the virtual pc hash table for the fast lookup */ >> - atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb); >> - return tb; >> -} >> - >> -static inline TranslationBlock *tb_find_fast(CPUState *cpu, >> +static inline TranslationBlock *tb_find(CPUState *cpu, >> TranslationBlock **last_tb, >> int tb_exit) >> { >> @@ -332,7 +294,34 @@ static inline TranslationBlock >> *tb_find_fast(CPUState *cpu, >> tb = atomic_read(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)]); >> if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base || >> tb->flags != flags)) { >> - tb = tb_find_slow(cpu, pc, cs_base, flags); >> + /* Ensure that we won't find a TB in the shared hash table >> + * if it is being invalidated by some other thread. >> + * Otherwise we'd put it back to CPU's local cache. >> + * Pairs with smp_wmb() in tb_phys_invalidate(). */ >> + smp_rmb(); >> + tb = tb_find_physical(cpu, pc, cs_base, flags); >> + if (!tb) { >> + >> + /* mmap_lock is needed by tb_gen_code, and mmap_lock must be >> + * taken outside tb_lock. As system emulation is currently >> + * single threaded the locks are NOPs. Both locks are to be >> + * released at the end of the function. >> + */ >> + mmap_lock(); >> + tb_lock(); >> + >> + /* There's a chance that our desired tb has been translated >> while >> + * taking the locks so we check again inside the lock. >> + */ >> + tb = tb_find_physical(cpu, pc, cs_base, flags); >> + if (!tb) { >> + /* if no translated code available, then translate it >> now */ >> + tb = tb_gen_code(cpu, pc, cs_base, flags, 0); >> + } >> + } >> + >> + /* We add the TB in the virtual pc hash table for the fast >> lookup */ >> + atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb); >> } >> if (cpu->tb_flushed) { >> /* Ensure that no TB jump will be modified as the >> @@ -440,7 +429,7 @@ static inline bool cpu_handle_exception(CPUState >> *cpu, int *ret) >> && cpu->icount_decr.u16.low + cpu->icount_extra == 0) { >> /* try to cause an exception pending in the log */ >> TranslationBlock *last_tb = NULL; /* Avoid chaining TBs */ >> - cpu_exec_nocache(cpu, 1, tb_find_fast(cpu, &last_tb, 0), true); >> + cpu_exec_nocache(cpu, 1, tb_find(cpu, &last_tb, 0), true); >> *ret = -1; >> return true; >> #endif >> @@ -624,7 +613,7 @@ int cpu_exec(CPUState *cpu) >> cpu->tb_flushed = false; /* reset before first TB lookup */ >> for(;;) { >> cpu_handle_interrupt(cpu, &last_tb); >> - tb = tb_find_fast(cpu, &last_tb, tb_exit); >> + tb = tb_find(cpu, &last_tb, tb_exit); >> cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit, &sc); >> /* Try to align the host and virtual clocks >> if the guest is in advance */ >> >> > > Using goto statements, the lines from tb_find_slow() which take the > locks can even be on the same indentation level as the lines resetting > them. I could prepare a patch series based on your first 3 patches and > this idea. Sure, lets see what it looks like ;-) > > Regards, > Sergey > >> >> >>>> } >>>> >>>> /* We add the TB in the virtual pc hash table for the fast lookup */ >>>> @@ -354,10 +352,15 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu, >>>> #endif >>>> /* See if we can patch the calling TB. */ >>>> if (*last_tb && !qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) { >>>> - tb_lock(); >>>> + if (!tb_lock_locked()) { >>>> + tb_lock(); >>>> + } >>>> tb_add_jump(*last_tb, tb_exit, tb); >>>> - tb_unlock(); >>>> } >>>> + >>>> + tb_lock_reset(); >>>> + mmap_lock_reset(); >>>> + >>>> return tb; >>>> } >>> -- >>> Alex Bennée -- Alex Bennée
diff --git a/cpu-exec.c b/cpu-exec.c index 54c935039592..ff8f92bc1dc1 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -278,45 +278,7 @@ static TranslationBlock *tb_find_physical(CPUState *cpu, return qht_lookup(&tcg_ctx.tb_ctx.htable, tb_cmp, &desc, h); } -static TranslationBlock *tb_find_slow(CPUState *cpu, - target_ulong pc, - target_ulong cs_base, - uint32_t flags) -{ - TranslationBlock *tb; - - /* Ensure that we won't find a TB in the shared hash table - * if it is being invalidated by some other thread. - * Otherwise we'd put it back to CPU's local cache. - * Pairs with smp_wmb() in tb_phys_invalidate(). */ - smp_rmb(); - tb = tb_find_physical(cpu, pc, cs_base, flags); - if (!tb) { - - /* mmap_lock is needed by tb_gen_code, and mmap_lock must be - * taken outside tb_lock. As system emulation is currently - * single threaded the locks are NOPs. Both locks are to be - * released at the end of tb_find_fast(). - */ - mmap_lock(); - tb_lock(); - - /* There's a chance that our desired tb has been translated while - * taking the locks so we check again inside the lock. - */ - tb = tb_find_physical(cpu, pc, cs_base, flags); - if (!tb) { - /* if no translated code available, then translate it now */ - tb = tb_gen_code(cpu, pc, cs_base, flags, 0); - } - } - - /* We add the TB in the virtual pc hash table for the fast lookup */ - atomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb); - return tb; -} - -static inline TranslationBlock *tb_find_fast(CPUState *cpu, +static inline TranslationBlock *tb_find(CPUState *cpu, TranslationBlock **last_tb, int tb_exit)