lkml.org 
[lkml]   [2013]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRegression: ftdi_sio is slow (since Wed Oct 10 15:05:06 2012)
Hi.

We have a regression because of this patch:
http://lkml.indiana.edu/hypermail/linux/kernel/1210.1/01456.html
While it is arguably reasonable to have this for tcdrain or close,
it also slows down poll/select a lot because n_tty_poll() does this:

tty_chars_in_buffer(tty) < WAKEUP_CHARS

And it also slows down TIOCOUTQ ioctl I think (not measured).
The slowdown of select() is big, the customer reports the inability
to work that way.

Is this patch really needed? I mean, if the time to check TEMT is
longer than to xmit that char, then what's the use?
Or, if it is really a big deal, I guess it would be necessary to add
a separate, .chars_in_buffer_fast method.

Thoughts?


\
 
 \ /
  Last update: 2013-05-03 16:21    [W:0.074 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site