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File qemu-0.11-git-user-linux-don-t-do-locking-in-single-threaded-proc.patch of Package qemu-svn (Revision 11)
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From f06038e90fe4eb5dd8c73735356125ab0d3e899b Mon Sep 17 00:00:00 2001 From: Ulrich Hecht <uli@suse.de> Date: Wed, 22 Jul 2009 14:03:19 +0200 Subject: [PATCH 25/33] linux-user: don't do locking in single-threaded processes Skips setting the tb_lock if a process doesn't have more than one thread, which is usually the case. Results in about 20% performance gain (measured with the s390x target, but the effect should be similar with other targets). Signed-off-by: Ulrich Hecht <uli@suse.de> --- cpu-defs.h | 8 ++++++++ cpu-exec.c | 14 ++++++++++++-- linux-user/syscall.c | 1 + 3 files changed, 21 insertions(+), 2 deletions(-) diff --git a/cpu-defs.h b/cpu-defs.h index d73ec0a..27e5bb2 100644 --- a/cpu-defs.h +++ b/cpu-defs.h @@ -135,6 +135,13 @@ typedef struct CPUWatchpoint { } CPUWatchpoint; #define CPU_TEMP_BUF_NLONGS 128 + +#ifdef CONFIG_USER_ONLY +#define MULTITHREAD uint32_t multithreaded; +#else +#define MULTITHREAD +#endif + #define CPU_COMMON \ struct TranslationBlock *current_tb; /* currently executing TB */ \ /* soft mmu support */ \ @@ -149,6 +156,7 @@ typedef struct CPUWatchpoint { uint32_t stop; /* Stop request */ \ uint32_t stopped; /* Artificially stopped */ \ uint32_t interrupt_request; \ + MULTITHREAD /* needs locking when accessing TBs */ \ volatile sig_atomic_t exit_request; \ /* The meaning of the MMU modes is defined in the target code. */ \ CPUTLBEntry tlb_table[NB_MMU_MODES][CPU_TLB_SIZE]; \ diff --git a/cpu-exec.c b/cpu-exec.c index 855ea3e..1371ce4 100644 --- a/cpu-exec.c +++ b/cpu-exec.c @@ -219,6 +219,9 @@ int cpu_exec(CPUState *env1) TranslationBlock *tb; uint8_t *tc_ptr; unsigned long next_tb; +#ifdef CONFIG_USER_ONLY + uint32_t multithreaded; +#endif if (cpu_halted(env1) == EXCP_HALTED) return EXCP_HALTED; @@ -604,7 +607,11 @@ int cpu_exec(CPUState *env1) #endif } #endif - spin_lock(&tb_lock); +#ifdef CONFIG_USER_ONLY + multithreaded = env->multithreaded; + if (multithreaded) +#endif + spin_lock(&tb_lock); tb = tb_find_fast(); /* Note: we do it here to avoid a gcc bug on Mac OS X when doing it in tb_find_slow */ @@ -632,7 +639,10 @@ int cpu_exec(CPUState *env1) tb_add_jump((TranslationBlock *)(next_tb & ~3), next_tb & 3, tb); } } - spin_unlock(&tb_lock); +#ifdef CONFIG_USER_ONLY + if (multithreaded) +#endif + spin_unlock(&tb_lock); env->current_tb = tb; /* cpu_interrupt might be called while translating the diff --git a/linux-user/syscall.c b/linux-user/syscall.c index e9b07df..f7a411d 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -3560,6 +3560,7 @@ static int do_fork(CPUState *env, unsigned int flags, abi_ulong newsp, ts = qemu_mallocz(sizeof(TaskState) + NEW_STACK_SIZE); init_task_state(ts); new_stack = ts->stack; + env->multithreaded = 1; /* we create a new CPU instance. */ new_env = cpu_copy(env); /* Init regs that differ from the parent. */ -- 1.6.2.1