From: Stas Sergeev <stsp@list.ru>
To: Jarkko Huijts <jarkko.huijts@gmail.com>
Cc: Alan Cox <alan@linux.intel.com>,
Linux kernel <linux-kernel@vger.kernel.org>,
Caylan Van Larson <i@caylan.net>,
"Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Regression: ftdi_sio is slow (since Wed Oct 10 15:05:06 2012)
Date: Fri, 03 May 2013 19:02:46 +0400 [thread overview]
Message-ID: <5183D196.2080305@list.ru> (raw)
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?
next reply other threads:[~2013-05-03 14:13 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-03 15:02 Stas Sergeev [this message]
2013-05-03 16:30 ` Regression: ftdi_sio is slow (since Wed Oct 10 15:05:06 2012) Greg KH
2013-05-03 17:38 ` Stas Sergeev
2013-05-03 16:52 ` Greg KH
2013-05-03 18:05 ` Stas Sergeev
2013-05-03 17:16 ` Greg KH
2013-05-03 18:27 ` Stas Sergeev
2013-05-03 18:27 ` Stas Sergeev
2013-05-03 20:34 ` Greg KH
2013-05-03 20:34 ` Greg KH
[not found] ` <20130503203419.GA25932-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2013-05-03 21:50 ` Stas Sergeev
2013-05-03 21:50 ` Stas Sergeev
2013-05-04 11:15 ` Johan Hovold
2013-05-04 11:15 ` Johan Hovold
2013-05-04 11:39 ` Peter Hurley
2013-05-05 18:29 ` Johan Hovold
2013-05-05 18:32 ` [PATCH 0/7] USB: serial: add wait_until_sent-support Johan Hovold
2013-05-05 18:32 ` [PATCH 1/7] USB: serial: add wait_until_sent operation Johan Hovold
[not found] ` <1367778753-22297-1-git-send-email-jhovold-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2013-05-05 18:32 ` [PATCH 2/7] USB: serial: add generic wait_until_sent implementation Johan Hovold
2013-05-05 18:32 ` Johan Hovold
2013-05-08 14:25 ` Stas Sergeev
2013-05-08 14:25 ` Stas Sergeev
2013-05-08 15:48 ` Johan Hovold
2013-05-08 15:48 ` Johan Hovold
2013-05-08 15:51 ` [PATCH v2 2/8] " Johan Hovold
2013-05-05 18:32 ` [PATCH 3/7] USB: ftdi_sio: clean up get_modem_status Johan Hovold
2013-05-05 18:32 ` [PATCH 4/7] USB: ftdi_sio: fix chars_in_buffer overhead Johan Hovold
2013-05-05 18:32 ` [PATCH 5/7] USB: io_ti: " Johan Hovold
2013-05-05 18:32 ` [PATCH 6/7] USB: ti_usb_3410_5052: " Johan Hovold
2013-05-05 18:32 ` [PATCH 7/7] USB: serial: clean up chars_in_buffer Johan Hovold
[not found] ` <81D166EE-BB85-4A72-A6FA-A1F6B5633CB0@caylan.net>
2013-05-20 10:07 ` [PATCH 0/7] USB: serial: add wait_until_sent-support Johan Hovold
2013-05-04 12:44 ` Regression: ftdi_sio is slow (since Wed Oct 10 15:05:06 2012) Stas Sergeev
2013-05-04 12:44 ` Stas Sergeev
2013-05-04 9:37 ` Stas Sergeev
2013-05-04 9:37 ` Stas Sergeev
2013-05-03 18:15 ` Stas Sergeev
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