Re: [PATCH 0/2] Better handling of slow remote transfers

Pedro Alves
2015-08-12T15:31:48Z

On 08/12/2015 04:08 PM, Gary Benson wrote:
> Pedro Alves wrote:
>> On 08/12/2015 02:58 PM, Pedro Alves wrote:
>>> GDB will usually cap the transfers to before they get to the
>>> lower layers. E.g., look for 4096 in memory_xfer_partial,
>>> target_read_alloc_1 and target_fileio_read_alloc_1.
>>>
>>> As this request is coming from the BFD side, we should probably
>>> make remote_hostio_pread also cap the size of the vFile:pread
>>> request. A reasonable number like a few KBs should not
>>> introduce any noticeable slow down.
>>
>> But wait, I'm now confused -- isn't this a red herring? Since
>> gdbserver is already limiting transfers to PBUFSIZE, this change
>> should have no practical effect, right?
>>
>> How can BFD's large remote_hostio_pread result in large vFile:pread:
>> packet responses then?
>
> I think gdbserver is returning multiple packets but something in GDB
> (getpkt_or_notif_sane_1?) is concatenating them together somehow.

No, getpkt_or_notif_sane_1 will return as soon as it has a single
packet, which should then be bubbling up the layers and reaching
gdb_bfd_iovec_fileio_pread. Something else is going on.
Either the QUIT is being lost/eaten, or ... hmm ... maybe the
SIGINT handler is set to remote.c:async_handle_remote_sigint
when the ctrl-c is typed, which means the ctrl-c doesn't
actually set_quit_flag()?

Thanks,
Pedro Alves