From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin@cygwin.com
Subject: Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?
Date: Fri, 27 Aug 2021 20:24:40 +0900 [thread overview]
Message-ID: <20210827202440.47706fc2fc07c5e9a1bc0047@nifty.ne.jp> (raw)
In-Reply-To: <3b560051-ab27-f392-ca4b-d1fd9b5733b0@cornell.edu>
[-- Attachment #1: Type: text/plain, Size: 8082 bytes --]
On Thu, 26 Aug 2021 18:18:29 -0400
Ken Brown wrote:
> On 8/26/2021 11:56 AM, Ken Brown via Cygwin wrote:
> > On 8/25/2021 5:29 PM, Takashi Yano wrote:
> >> On Wed, 25 Aug 2021 13:52:19 -0400
> >> Ken Brown wrote:
> >>> On 8/25/2021 7:18 AM, Takashi Yano via Cygwin wrote:
> >>>> On Tue, 24 Aug 2021 12:49:52 -0700
> >>>> Chris Roehrig wrote:
> >>>>> I have a network of Windows, Linux and Mac machines and I use rsync to
> >>>>> synchronize various directories between them.
> >>>>>
> >>>>> I'm trying to figure out why my rsync transfers are so slow (<4 MB/s) only
> >>>>> when the remote endpoint is Cygwin rsync over sshd (with both a Linux or
> >>>>> Cygwin rsync client). In all other scenarios, I get the full 100MB/s as
> >>>>> expected from gigabit ethernet. This has been an ongoing problem for me
> >>>>> for a couple of years over several Windows and Cygwin versions, and I'd
> >>>>> like to try to fix it.
> >>>>>
> >>>>> If I run rsync --daemon --no-detach under mintty in the foreground on the
> >>>>> remote Windows endpoint, I get the full 100 MB/s transfers, so it seems
> >>>>> like it has something to do with rsync.exe running in the background under
> >>>>> the cygrunsrv+sshd service (which was installed normally using
> >>>>> ssh-host-config).
> >>>>>
> >>>>> If I do:
> >>>>> pv /dev/zero | ssh $WINHOST "cat > /dev/null"
> >>>>> or even
> >>>>> pv /dev/urandom | ssh $WINHOST md5sum
> >>>>> I also get the full 100 MB/s transfers, so it doesn't look like sshd itself
> >>>>> is being throttled by bandwidth or CPU.
> >>>>>
> >>>>> The machines have less than 15% CPU utilization while transferring, with
> >>>>> each of the 4 cores less than 30%, so it doesn't look to be CPU issue.
> >>>>> In Task Manager, sshd.exe and rsync.exe seem to be running normally using
> >>>>> only few percent CPU, and show Power Throttling=Disabled,
> >>>>> Priority=Normal. Setting their Priority to High doesn't seem to change
> >>>>> things.
> >>>>>
> >>>>> Looking in Resource Monitor on the remote endpoint, the network usage is
> >>>>> pretty much a flat horizontal line at about 18 Mbps (2.5 MB/s), so it sure
> >>>>> looks to me as if rsync is somehow being bandwidth-throttled\b when run in
> >>>>> the background under cygsshd.
> >>>>>
> >>>>> It's almost as if rsync has an implicit --bwlimit override when it is run
> >>>>> from cygrunsrv+sshd (I've tried --bwlimit=0 on the client which makes no
> >>>>> difference).
> >>>>>
> >>>>>
> >>>>> Any ideas? Not sure where to go from here.
> >>>>
> >>>> In cygwin, just scp is very slow.
> >>>>
> >>>> The transfer speed in my environment is as follows.
> >>>> The tests were done with 100MB of test.dat file.
> >>>>
> >>>> (1-1) From cygwin-PC,
> >>>> [yano@cygwin-PC ~]$ scp test.dat yano@linux-server:.
> >>>> yano@linux-server's password:
> >>>> test.dat 100% 100MB 4.0MB/s 00:24
> >>>> [yano@cygwin-PC ~]$ scp yano@linux-server:test.dat .
> >>>> yano@linux-server's password:
> >>>> test.dat 100% 100MB 8.0MB/s 00:12
> >>>>
> >>>> (1-2) From linux-server,
> >>>> yano@linux-server:~$ scp yano@cygwin-PC:test.dat .
> >>>> yano@cygwin-PC's password:
> >>>> test.dat 100% 100MB 4.0MB/s 00:24
> >>>> yano@linux-server:~$ scp test.dat yano@cygwin-PC:.
> >>>> yano@cygwin-PC's password:
> >>>> test.dat 100% 100MB 4.1MB/s 00:24
> >>>>
> >>>>
> >>>> I looked into this problem, and noticed that this is caused
> >>>> by cygwin pipe implementation. Pipe in cygwin is configured
> >>>> with FILE_FLAG_OVERLAPPED.
> >>>>
> >>>> If the pipe is configured without FILE_FLAG_OVERLAPPED,
> >>>> the transfer speed is much improved as follows.
> >>>>
> >>>>
> >>>> (2-1) From cygwin-PC,
> >>>> [yano@cygwin-PC ~]$ scp test.dat yano@linux-server:.
> >>>> yano@linux-server's password:
> >>>> test.dat 100% 100MB 85.5MB/s 00:01
> >>>> [yano@cygwin-PC ~]$ scp yano@linux-server:test.dat .
> >>>> yano@linux-server's password:
> >>>> test.dat 100% 100MB 69.7MB/s 00:01
> >>>>
> >>>> (2-2) From linux-server,
> >>>> yano@linux-server:~$ scp yano@cygwin-PC:test.dat .
> >>>> yano@cygwin-PC's password:
> >>>> test.dat 100% 100MB 80.1MB/s 00:01
> >>>> yano@linux-server:~$ scp test.dat yano@cygwin-PC:.
> >>>> yano@cygwin-PC's password:
> >>>> test.dat 100% 100MB 57.7MB/s 00:01
> >>>>
> >>>> I am not sure why this happens and how to fix this.
> >>>
> >>> A couple years ago I had an idea for changing the pipe implementation to avoid
> >>> overlapped I/O:
> >>>
> >>> https://cygwin.com/pipermail/cygwin-patches/2019q2/009393.html
> >>> https://cygwin.com/pipermail/cygwin-patches/2019q2/009423.html
> >>>
> >>> I never followed up on it. But if you think it might help with this problem, I
> >>> could dust it off and try to finish it.
> >>
> >> Interesting.
> >>
> >> It will be also helpfull for:
> >> https://cygwin.com/pipermail/cygwin/2021-March/247987.html
> >> which seems to be the same issue with
> >> https://stackoverflow.com/questions/10385424/good-alternatives-to-cygwin-cygwin-doesnt-support-natively-support-win32-app
> >>
> >>
> >> However, I wonder why scp dislikes overlapped I/O.
> >
> > I agree that it would be good to understand this. When I first proposed the
> > change, I was thinking in terms of code simplification. If it also improves
> > performance (which we don't know yet), it becomes a higher priority, but in that
> > case it would be nice to understand why it improves performance.
>
> Hi Takashi,
>
> In case you want to try out my proposed change, I've just rebased the patches to
> the current master and pushed them to a new topic/pipe branch.
Hi Ken,
Thanks much! I tested topic/pipe branch.
[yano@cygwin-PC ~]$ scp test.dat yano@linux-server:.
yano@linux-server's password:
test.dat 100% 100MB 95.9MB/s 00:01
[yano@cygwin-PC ~]$ scp yano@linux-server:test.dat .
yano@linux-server's password:
test.dat 100% 100MB 8.0MB/s 00:12
yano@linux-server:~$ scp yano@cygwin-PC:test.dat .
yano@cygwin-PC's password:
test.dat 100% 100MB 109.7MB/s 00:00
yano@linux-server:~$ scp test.dat yano@cygwin-PC:.
yano@cygwin-PC's password:
test.dat 100% 100MB 31.4MB/s 00:03
As shown above, outgoing transfer-rate has been improved upto near
theoretical limit. However, incoming transfer-rate is not improved
much.
I digged further and found the first patch attached solves the issue
as follows.
[yano@cygwin-PC ~]$ scp yano@linux-server:test.dat .
yano@linux-server's password:
test.dat 100% 100MB 112.8MB/s 00:00
yano@linux-server2:~$ scp test.dat yano@cygwin-PC:.
yano@cygwin-PC's password:
test.dat 100% 100MB 102.5MB/s 00:00
I also tested the case:
> >> https://cygwin.com/pipermail/cygwin/2021-March/247987.html
> >> which seems to be the same issue with
> >> https://stackoverflow.com/questions/10385424/good-alternatives-to-cygwin-cygwin-doesnt-support-natively-support-win32-app
Unfortunately, topic/pipe does not help.
I confirmed that applying the second patch attached, which reverts
to create() rather than nt_create(), and setting CYGWIN=pipe_byte
fixes the problem.
What do you think of this alternative implementation which does
not use nt_create()?
--
Takashi Yano <takashi.yano@nifty.ne.jp>
[-- Attachment #2: 0001-Cygwin-select-Improve-select-poll-response.patch --]
[-- Type: application/octet-stream, Size: 2460 bytes --]
From c2ececea731fb633a9e10666d7546e1c61c8c4f7 Mon Sep 17 00:00:00 2001
From: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Fri, 27 Aug 2021 19:54:41 +0900
Subject: [PATCH 1/2] Cygwin: select: Improve select/poll response.
---
winsup/cygwin/select.cc | 32 ++++++++++++++++++++++++++++----
1 file changed, 28 insertions(+), 4 deletions(-)
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 8ad982c12..83e1c00e0 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -735,6 +735,7 @@ thread_pipe (void *arg)
select_pipe_info *pi = (select_pipe_info *) arg;
DWORD sleep_time = 0;
bool looping = true;
+ DWORD t0 = GetTickCount ();
while (looping)
{
@@ -754,7 +755,12 @@ thread_pipe (void *arg)
break;
cygwait (pi->bye, sleep_time >> 3);
if (sleep_time < 80)
- ++sleep_time;
+ {
+ DWORD t1 = GetTickCount ();
+ if (t0 != t1)
+ ++sleep_time;
+ t0 = t1;
+ }
if (pi->stop_thread)
break;
}
@@ -930,6 +936,7 @@ thread_fifo (void *arg)
select_fifo_info *pi = (select_fifo_info *) arg;
DWORD sleep_time = 0;
bool looping = true;
+ DWORD t0 = GetTickCount ();
while (looping)
{
@@ -949,7 +956,12 @@ thread_fifo (void *arg)
break;
cygwait (pi->bye, sleep_time >> 3);
if (sleep_time < 80)
- ++sleep_time;
+ {
+ DWORD t1 = GetTickCount ();
+ if (t0 != t1)
+ ++sleep_time;
+ t0 = t1;
+ }
if (pi->stop_thread)
break;
}
@@ -1125,6 +1137,7 @@ thread_console (void *arg)
select_console_info *ci = (select_console_info *) arg;
DWORD sleep_time = 0;
bool looping = true;
+ DWORD t0 = GetTickCount ();
while (looping)
{
@@ -1144,7 +1157,12 @@ thread_console (void *arg)
break;
cygwait (ci->bye, sleep_time >> 3);
if (sleep_time < 80)
- ++sleep_time;
+ {
+ DWORD t1 = GetTickCount ();
+ if (t0 != t1)
+ ++sleep_time;
+ t0 = t1;
+ }
if (ci->stop_thread)
break;
}
@@ -1364,6 +1382,7 @@ thread_pty_slave (void *arg)
select_pipe_info *pi = (select_pipe_info *) arg;
DWORD sleep_time = 0;
bool looping = true;
+ DWORD t0 = GetTickCount ();
while (looping)
{
@@ -1383,7 +1402,12 @@ thread_pty_slave (void *arg)
break;
cygwait (pi->bye, sleep_time >> 3);
if (sleep_time < 80)
- ++sleep_time;
+ {
+ DWORD t1 = GetTickCount ();
+ if (t0 != t1)
+ ++sleep_time;
+ t0 = t1;
+ }
if (pi->stop_thread)
break;
}
--
2.33.0
[-- Attachment #3: 0002-Cygwin-pipe-Revert-to-create-rather-than-nt_create.patch --]
[-- Type: application/octet-stream, Size: 2368 bytes --]
From 784892dc272a6b7899de5f89c65bb8cfab79591d Mon Sep 17 00:00:00 2001
From: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Fri, 27 Aug 2021 20:06:04 +0900
Subject: [PATCH 2/2] Cygwin: pipe: Revert to create() rather than nt_create().
---
winsup/cygwin/fhandler_pipe.cc | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/winsup/cygwin/fhandler_pipe.cc b/winsup/cygwin/fhandler_pipe.cc
index 2dec0a848..b3af4a0a0 100644
--- a/winsup/cygwin/fhandler_pipe.cc
+++ b/winsup/cygwin/fhandler_pipe.cc
@@ -234,6 +234,24 @@ fhandler_pipe::raw_read (void *ptr, size_t& len)
return;
}
+ if (is_nonblocking ())
+ {
+ DWORD n;
+ BOOL ret = PeekNamedPipe (get_handle (), NULL, 0, NULL, &n, NULL);
+ if (!ret)
+ {
+ __seterrno ();
+ len = (size_t) -1;
+ return;
+ }
+ if (n == 0)
+ {
+ set_errno (EAGAIN);
+ len = (size_t) -1;
+ return;
+ }
+ }
+
do
{
len = orig_len;
@@ -571,6 +589,7 @@ fhandler_pipe::create (LPSECURITY_ATTRIBUTES sa_ptr, PHANDLE r, PHANDLE w,
return 0;
}
+#if 0
/* The next version of fhandler_pipe::create used to call the previous
version. But the read handle created by the latter doesn't have
FILE_WRITE_ATTRIBUTES access unless the pipe is created with
@@ -588,6 +607,7 @@ fhandler_pipe::create (LPSECURITY_ATTRIBUTES sa_ptr, PHANDLE r, PHANDLE w,
static int nt_create (LPSECURITY_ATTRIBUTES, PHANDLE, PHANDLE, DWORD,
int64_t *);
+#endif
int
fhandler_pipe::create (fhandler_pipe *fhs[2], unsigned psize, int mode)
@@ -597,7 +617,7 @@ fhandler_pipe::create (fhandler_pipe *fhs[2], unsigned psize, int mode)
int res = -1;
int64_t unique_id;
- int ret = nt_create (sa, &r, &w, psize, &unique_id);
+ int ret = create (sa, &r, &w, psize, NULL, 0, &unique_id);
if (ret)
__seterrno_from_win_error (ret);
else if ((fhs[0] = (fhandler_pipe *) build_fh_dev (*piper_dev)) == NULL)
@@ -624,6 +644,7 @@ fhandler_pipe::create (fhandler_pipe *fhs[2], unsigned psize, int mode)
return res;
}
+#if 0
static int
nt_create (LPSECURITY_ATTRIBUTES sa_ptr, PHANDLE r, PHANDLE w,
DWORD psize, int64_t *unique_id)
@@ -755,6 +776,7 @@ nt_create (LPSECURITY_ATTRIBUTES sa_ptr, PHANDLE r, PHANDLE w,
/* Success. */
return 0;
}
+#endif
int
fhandler_pipe::ioctl (unsigned int cmd, void *p)
--
2.33.0
next prev parent reply other threads:[~2021-08-27 11:25 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-24 19:49 Chris Roehrig
2021-08-24 23:43 ` Mark Geisert
2021-08-25 0:35 ` Chris Roehrig
2021-08-25 2:12 ` Chris Roehrig
2021-08-25 2:02 ` NightStrike
2021-08-25 3:20 ` Mark Geisert
2021-08-25 17:24 ` Chris Roehrig
2021-08-25 11:18 ` Takashi Yano
2021-08-25 17:31 ` Chris Roehrig
2021-08-25 17:52 ` Ken Brown
2021-08-25 18:18 ` Chris Roehrig
2021-08-25 18:51 ` Chris Roehrig
2021-08-26 15:44 ` Ken Brown
2021-08-25 20:33 ` Mario Emmenlauer
2021-08-26 15:47 ` Ken Brown
2021-08-25 21:29 ` Takashi Yano
2021-08-26 15:56 ` Ken Brown
2021-08-26 22:18 ` Ken Brown
2021-08-27 11:24 ` Takashi Yano [this message]
2021-08-27 16:00 ` Ken Brown
2021-08-27 17:21 ` Takashi Yano
2021-08-28 2:00 ` Takashi Yano
2021-08-28 3:03 ` Takashi Yano
2021-08-28 8:43 ` Corinna Vinschen
2021-08-28 9:41 ` Takashi Yano
2021-08-28 11:58 ` Corinna Vinschen
2021-08-28 15:43 ` Takashi Yano
2021-08-28 20:55 ` Ken Brown
2021-08-29 8:41 ` Takashi Yano
2021-08-29 22:42 ` Ken Brown
2021-08-29 10:27 ` Corinna Vinschen
2021-08-29 9:07 ` Takashi Yano
2021-08-29 15:57 ` Ken Brown
2021-08-29 19:24 ` Chris Roehrig
2021-08-29 22:24 ` Ken Brown
2021-08-30 23:58 ` Chris Roehrig
2021-08-31 19:05 ` Ken Brown
2021-08-31 19:53 ` Chris Roehrig
2021-08-31 20:23 ` Chris Roehrig
2021-08-31 21:29 ` Brian Inglis
2021-09-01 21:11 ` Chris Roehrig
2021-09-02 15:25 ` Ken Brown
2021-09-02 19:03 ` Chris Roehrig
2021-09-03 17:26 ` Ken Brown
2021-09-03 19:55 ` Corinna Vinschen
2021-09-03 20:59 ` Chris Roehrig
2021-09-04 8:32 ` Achim Gratz
2021-09-04 16:45 ` Brian Inglis
2021-09-05 8:18 ` Achim Gratz
2021-09-05 15:11 ` Brian Inglis
2021-09-06 10:42 ` Achim Gratz
2021-09-04 22:37 ` mmap failure [was: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?] Ken Brown
2021-09-04 22:54 ` Ken Brown
2021-09-04 22:58 ` Ken Brown
2021-09-05 0:04 ` Ken Brown
2021-09-05 13:24 ` Ken Brown
2021-09-06 15:32 ` Corinna Vinschen
2021-09-06 17:12 ` Ken Brown
2021-09-06 17:38 ` Ken Brown
2021-09-06 17:43 ` Eliot Moss
2021-09-06 17:59 ` Corinna Vinschen
2021-09-06 18:07 ` Corinna Vinschen
2021-09-06 18:40 ` Ken Brown
2021-09-06 20:52 ` Peter Dons Tychsen
2021-09-06 20:54 ` Peter Dons Tychsen
2021-09-06 21:24 ` Ken Brown
2021-09-06 21:31 ` Ken Brown
2021-09-07 3:34 ` Brian Inglis
2021-09-07 16:28 ` Ken Brown
2021-09-07 21:52 ` Lavrentiev, Anton (NIH/NLM/NCBI) [C]
2021-09-07 22:44 ` Ken Brown
2021-09-08 6:14 ` Sam Edge
2021-09-08 8:18 ` Corinna Vinschen
2021-09-07 21:41 ` Peter Dons Tychsen
2021-09-04 23:18 ` Brian Inglis
2021-08-29 19:37 ` cygrunsrv + sshd + rsync = 20 times too slow -- throttled? Takashi Yano
2021-08-29 21:09 ` Ken Brown
2021-08-29 21:04 ` Ken Brown
2021-08-30 0:13 ` Takashi Yano
2021-08-30 0:22 ` Takashi Yano
2021-08-30 2:15 ` Ken Brown
2021-08-30 8:02 ` Takashi Yano
2021-08-28 15:17 ` Ken Brown
2021-09-16 22:00 ` Keith Christian
2021-09-16 22:48 ` Ken Brown
2021-09-16 22:58 ` Keith Christian
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