From: Torge Matthies tmatthies@codeweavers.com
Credits to Avi Kivity (scylladb) and Aliaksei Kandratsenka (gperftools) for this trick, see [1].
[1] https://github.com/scylladb/seastar/commit/77a58e4dc020233f66fccb8d9e8f7a8b7... --- dlls/ntdll/unix/virtual.c | 50 +++++++++++++++++++++++++++++++++++++- tools/winapi/nativeapi.dat | 1 + 2 files changed, 50 insertions(+), 1 deletion(-)
diff --git a/dlls/ntdll/unix/virtual.c b/dlls/ntdll/unix/virtual.c index 0faf3e343e3..b1023c202b1 100644 --- a/dlls/ntdll/unix/virtual.c +++ b/dlls/ntdll/unix/virtual.c @@ -216,6 +216,9 @@ struct range_entry static struct range_entry *free_ranges; static struct range_entry *free_ranges_end;
+static void *dontneed_page; +static pthread_mutex_t dontneed_page_mutex = PTHREAD_MUTEX_INITIALIZER; +
static inline BOOL is_beyond_limit( const void *addr, size_t size, const void *limit ) { @@ -5170,13 +5173,58 @@ NTSTATUS WINAPI NtFlushInstructionCache( HANDLE handle, const void *addr, SIZE_T }
+static BOOL try_madvise( void ) +{ + static int once = 0; + BOOL success = FALSE; + char *mem; + + pthread_mutex_lock(&dontneed_page_mutex); + /* Credits to Avi Kivity (scylladb) and Aliaksei Kandratsenka (gperftools) for this trick, + see https://github.com/scylladb/seastar/commit/77a58e4dc020233f66fccb8d9e8f7a8b7... */ + mem = dontneed_page; + if (!mem) + { + int ret; + /* Allocate one page of memory that we can call madvise() on */ + mem = anon_mmap_alloc( page_size, PROT_READ | PROT_WRITE ); + if (mem == MAP_FAILED) + goto failed; + /* If the memory is locked, e.g. by a call to mlockall(MCL_FUTURE), the madvise() call below + will fail with error EINVAL, so unlock it here */ + ret = munlock( mem, page_size ); + /* munlock() may fail on old kernels if we don't have sufficient permissions, but that is not + a problem since in that case we didn't have permission to lock the memory either */ + if (ret && errno != EPERM) + goto failed; + dontneed_page = mem; + } + /* Force the page into memory to make madvise() have real work to do */ + *mem = 3; + /* Evict the page from memory to force the kernel to send an IPI to all threads of this process, + which has the side effect of executing a memory barrier in those threads */ + success = !madvise( mem, page_size, MADV_DONTNEED ); +#ifdef __aarch64__ + /* Some ARMv8 processors can broadcast TLB invalidations using the TLBI instruction, + the madvise trick does not work on those */ + if (success && !once++) + FIXME( "memory barrier may not work on this platform\n" ); +#endif +failed: + pthread_mutex_unlock(&dontneed_page_mutex); + return success; +} + + /********************************************************************** * NtFlushProcessWriteBuffers (NTDLL.@) */ void WINAPI NtFlushProcessWriteBuffers(void) { static int once = 0; - if (!once++) FIXME( "stub\n" ); + if (try_madvise()) + return; + if (!once++) FIXME( "no implementation available on this platform\n" ); }
diff --git a/tools/winapi/nativeapi.dat b/tools/winapi/nativeapi.dat index ade20b5ee68..5512c4f1833 100644 --- a/tools/winapi/nativeapi.dat +++ b/tools/winapi/nativeapi.dat @@ -134,6 +134,7 @@ log10 logb longjmp lseek +madvise malloc mblen memccpy