Re: ioengine=sync issue on Windows

[Jens Axboe <axboe@kernel.dk>]

On 2014-04-03 21:12, Bruce Cran wrote:
> On 4/3/2014 8:35 PM, Jens Axboe wrote:
>> So next question... If you replace that fill_io_buffer() call with a
>> memset(b, 0, bs); does it then work?
>>
>
> The io error goes away, but now it occasionally crashes:
>
> (gdb) bt
>
> #0  0x64942e9e in pthread_mutex_unlock () from
> /cygdrive/c/Users/bcran/workspace/fio/libwinpthread-1.dll
> #1  0x0043997c in run_threads () at backend.c:1791
> #2  0x00439d9f in fio_backend () at backend.c:1904
> #3  0x0044c274 in main (argc=2, argv=0x821728, envp=0x821988) at fio.c:50
>
> (gdb) info threads
>    Id   Target Id         Frame
>    3    Thread 7256.0x4618 fio_pin_memory (td=td@entry=0x2820000) at
> memory.c:27
>    2    Thread 7256.0xc8  0x7787bf3c in ?? ()
> * 1    Thread 7256.0x5e04 0x64942e9e in pthread_mutex_unlock () from
> /cygdrive/c/Users/bcran/workspace/fio/libwinpthread-1.dll
> (gdb) thread 3
> (gdb) bt
> #0  fio_pin_memory (td=td@entry=0x2820000) at memory.c:27
> #1  0x00437076 in thread_main (data=0x2820000) at backend.c:1226
> #2  0x64944ecb in pthread_create_wrapper () from
> /cygdrive/c/Users/bcran/workspace/fio/libwinpthread-1.dll
> #3  0x752d0bc4 in wtoi64 () from /cygdrive/c/Windows/SysWOW64/msvcrt.dll
> #4  0x752d0cec in msvcrt!_beginthreadex () from
> /cygdrive/c/Windows/SysWOW64/msvcrt.dll
> #5  0x7699495d in KERNEL32!BaseThreadInitThunk () from
> /cygdrive/c/Windows/SysWOW64/KERNEL32.DLL
> #6  0x778898ee in ?? ()
> #7  0x778898c4 in ?? ()
> #8  0x00000000 in ?? ()

This really sounds like an issue with write() on windows. The change 
looks fine, and the fact that moving the memset around makes a 
difference - well, that's just bizarre. Do you have time to dig into 
this? Was read/write really completely reliable before this change?

What if we allocate a bigger buffer, does that change anything? Change 
that malloc() to:

b = fio_memalign(4096, 2 * td->o.max_bs[DDIR_WRITE]);

(and the corresponding free to fio_memfree(b, 2 * td->o.max_bs[DDIR_WRITE])

-- 
Jens Axboe