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From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin-developers@cygwin.com
Subject: Re: cygrunsrv + sshd + rsync = 20 times too slow -- throttled?
Date: Sun, 5 Sep 2021 22:50:37 +0900	[thread overview]
Message-ID: <20210905225037.c625ee0bcd479181848763f8@nifty.ne.jp> (raw)
In-Reply-To: <20210905224059.cfdc8f23d3eeaa1ea16ecf2e@nifty.ne.jp>

On Sun, 5 Sep 2021 22:40:59 +0900
Takashi Yano wrote:
> On Sun, 5 Sep 2021 08:15:23 +0900
> Takashi Yano wrote:
> > Hi Ken,
> > 
> > On Sat, 4 Sep 2021 10:04:12 -0400
> > Ken Brown wrote:
> > > On 9/4/2021 8:37 AM, Takashi Yano wrote:
> > > > On Sat, 4 Sep 2021 21:02:58 +0900
> > > > Takashi Yano wrote:
> > > >> Hi Corinna, Ken,
> > > >>
> > > >> On Fri, 3 Sep 2021 09:27:37 -0400
> > > >> Ken Brown wrote:
> > > >>> On 9/3/2021 8:22 AM, Takashi Yano wrote:
> > > >>>> POSIX says:
> > > >>>>       The value returned may be less than nbyte if the number of bytes left
> > > >>>>       in the file is less than nbyte, if the read() request was interrupted
> > > >>>>       by a signal, or if the file is a pipe or FIFO or special file and has
> > > >>>>                                                                         ~~~
> > > >>>>       fewer than nbyte bytes immediately available for reading.
> > > >>>>       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >>>>
> > > >>>> https://pubs.opengroup.org/onlinepubs/009604599/functions/read.html
> > > >>>>
> > > >>>> If it is turned over, read() should read all data immediately available,
> > > >>>> I think.
> > > >>>
> > > >>> I understand the reasoning now, but I think your patch isn't quite right.  As it
> > > >>> stands, if the call to NtQueryInformationFile fails but total_length != 0,
> > > >>> you're trying to read again without knowing that there's data in the pipe.
> > > >>>
> > > >>> Also, I think you need the following:
> > > >>>
> > > >>> diff --git a/winsup/cygwin/fhandler_pipe.cc b/winsup/cygwin/fhandler_pipe.cc
> > > >>> index ef7823ae5..46bb96961 100644
> > > >>> --- a/winsup/cygwin/fhandler_pipe.cc
> > > >>> +++ b/winsup/cygwin/fhandler_pipe.cc
> > > >>> @@ -348,8 +348,13 @@ fhandler_pipe::raw_read (void *ptr, size_t& len)
> > > >>>        CloseHandle (evt);
> > > >>>      if (status == STATUS_THREAD_SIGNALED)
> > > >>>        {
> > > >>> -      set_errno (EINTR);
> > > >>> -      len = (size_t) -1;
> > > >>> +      if (total_len == 0)
> > > >>> +       {
> > > >>> +         set_errno (EINTR);
> > > >>> +         len = (size_t) -1;
> > > >>> +       }
> > > >>> +      else
> > > >>> +       len = total_len;
> > > >>>        }
> > > >>>      else if (status == STATUS_THREAD_CANCELED)
> > > >>>        pthread::static_cancel_self ();
> > > >>
> > > >> Thanks for your advice. I fixed the issue and attached new patch.
> > > >>
> > > >> On Fri, 3 Sep 2021 17:37:13 +0200
> > > >> Corinna Vinschen wrote:
> > > >>> Hmm, I see the point, but we might have another problem with that.
> > > >>>
> > > >>> We can't keep the mutex while waiting on the pending read, and there
> > > >>> could be more than one pending read running at the time.  if so,
> > > >>> chances are extremly high, that the data written to the buffer gets
> > > >>> split like this:
> > > >>>
> > > >>>     reader 1		               reader 2
> > > >>>
> > > >>>     calls read(65536)                   calls read(65536)
> > > >>>
> > > >>>     calls NtReadFile(16384 bytes)
> > > >>>                                         calls NtReadFile(16384 bytes)
> > > >>>
> > > >>> writer writes 65536 bytes
> > > >>>
> > > >>>     wakes up and gets 16384 bytes
> > > >>>                                         wakes up and gets 16384 bytes
> > > >>>     gets the mutex, calls
> > > >>>     NtReadFile(32768) which
> > > >>>     returns immediately with
> > > >>>     32768 bytes added to the
> > > >>>     caller's buffer.
> > > >>>
> > > >>> so the buffer returned to reader 1 is 49152 bytes, with 16384 bytes
> > > >>> missing in the middle of it, *without* the reader knowing about that
> > > >>> fact.  If reader 1 gets the first 16384 bytes, the 16384 bytes have
> > > >>> been read in a single call, at least, so the byte order is not
> > > >>> unknowingly broken on the application level.
> > > >>>
> > > >>> Does that make sense?
> > > >>
> > > >> Why can't we keep the mutex while waiting on the pending read?
> > > >> If we can keep the mutex, the issue above mentioned does not
> > > >> happen, right?
> > > >>
> > > >> What about the patch attached? This keeps the mutex while read()
> > > >> but I do not see any defects so far.
> > > 
> > > LGTM.
> > > 
> > > If Corinna agrees, I have a couple of suggestions.
> > > 
> > > 1. With this patch, we can no longer have more than one pending ReadFile.  So 
> > > there's no longer a need to count read handles, and the problem with select is 
> > > completely fixed as long as the number of bytes requested is less than the pipe 
> > > buffer size.
> > > 
> > > 2. raw_read is now reading in chunks, like raw_write.  For readability of the 
> > > code, I think it would be better to make the two functions as similar as 
> > > possible.  For example, you could replace the do/while loop by a 
> > > while(total_len<orig_len) loop.  And you could even use similar names for the 
> > > variables, e.g., nbytes instead of total_len, or vice versa.
> > 
> > Thanks for the suggestion. I have rebuilt the patch.
> > Please see the patch attached.
> 
> This patch seems to fail to adopt to current git head of topic/pipe
> branch. I rebuilt the patch to fit current top/pipe.
> 
> Please see the patch attached.

Small typo.

-	     pipe buffer size.  Every pending read lowers WriteQuotaAvailable
+	     pipe buffer size. pending read lowers WriteQuotaAvailable

should be:

-	     pipe buffer size.  Every pending read lowers WriteQuotaAvailable
+	     pipe buffer size. Pending read lowers WriteQuotaAvailable

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>

  reply	other threads:[~2021-09-05 13:50 UTC|newest]

Thread overview: 250+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <41A583E1-C8E7-42AB-9F24-EEC33A41EC60@house.org>
     [not found] ` <20210825201845.07b6400b79dc5558a7761efe@nifty.ne.jp>
     [not found]   ` <f8106fe7-a2b8-d106-3061-4d888124f4b0@cornell.edu>
     [not found]     ` <20210826062934.54f2f2216021c095bb7ba13b@nifty.ne.jp>
     [not found]       ` <d0a8c57d-1ed1-6b4f-c6e7-cbe0e2ec8a1c@cornell.edu>
     [not found]         ` <3b560051-ab27-f392-ca4b-d1fd9b5733b0@cornell.edu>
     [not found]           ` <20210827202440.47706fc2fc07c5e9a1bc0047@nifty.ne.jp>
     [not found]             ` <4f2cb5f3-ce9c-c617-f65f-841a5eca096e@cornell.edu>
     [not found]               ` <20210828022111.91ef5b4ff24f6da9fadb489e@nifty.ne.jp>
     [not found]                 ` <YSn3L0W1M527utK0@calimero.vinschen.de>
     [not found]                   ` <20210828184102.f2206a8a9e5fe5cf24bf5e45@nifty.ne.jp>
     [not found]                     ` <YSok0PoCQn2TPPrn@calimero.vinschen.de>
     [not found]                       ` <20210829004346.c2f80469abc3a07fd4b2918d@nifty.ne.jp>
     [not found]                         ` <e8caa02f-be85-33bc-3f09-347c1cdb0923@cornell.edu>
     [not found]                           ` <20210829174124.0c1ae6c16a3e8da1f490abc7@nifty.ne.jp>
     [not found]                             ` <6e9bb35e-6f4f-cf78-e515-549da487b5ef@cornell.edu>
2021-08-30  7:57                               ` Corinna Vinschen
     [not found]                     ` <20210829180729.48b4e877f773cb3980c5766d@nifty.ne.jp>
     [not found]                       ` <789f056a-f164-d71d-1dc9-230f5a41846d@cornell.edu>
2021-08-30  8:27                         ` Corinna Vinschen
2021-08-30 13:00                           ` Corinna Vinschen
2021-08-30 13:20                             ` Corinna Vinschen
2021-08-30 13:41                               ` Ken Brown
2021-08-30 14:12                                 ` Corinna Vinschen
2021-08-30 14:52                                   ` Ken Brown
2021-08-30 15:15                                     ` Corinna Vinschen
     [not found]                         ` <20210830043756.8aa0ada77db0bfbbe3889f62@nifty.ne.jp>
     [not found]                           ` <47e5dd74-b940-f305-fd5a-c6c9d8f41305@cornell.edu>
2021-08-30  8:48                             ` Corinna Vinschen
     [not found]                       ` <c62d18df-ab7a-7233-62ee-29a8eced5353@cornell.edu>
     [not found]                         ` <20210830091314.f9a2cb71794d0f68cdb5eba7@nifty.ne.jp>
     [not found]                           ` <20210830092259.52f7d54fc3fa340738373af4@nifty.ne.jp>
     [not found]                             ` <d217ef03-7858-5e22-0aa6-f0507eedd9da@cornell.edu>
     [not found]                               ` <20210830170204.fa91eaf110f310f13b67abc3@nifty.ne.jp>
2021-08-30 10:20                                 ` Corinna Vinschen
2021-08-30 10:38                                   ` Corinna Vinschen
2021-08-30 12:04                                   ` Takashi Yano
2021-08-30 12:55                                     ` Corinna Vinschen
2021-08-30 13:31                                       ` Corinna Vinschen
2021-08-31  8:50                                         ` Takashi Yano
2021-08-30 13:51                                       ` Ken Brown
2021-08-30 15:00                                         ` Ken Brown
2021-08-30 15:19                                           ` Corinna Vinschen
2021-08-30 15:43                                             ` Ken Brown
2021-08-31  9:43                                               ` Corinna Vinschen
2021-08-31  8:52                                             ` Takashi Yano
2021-08-31  9:04                                               ` Corinna Vinschen
2021-08-31 11:05                                                 ` Takashi Yano
2021-08-31 15:20                                                   ` Corinna Vinschen
2021-09-01  2:39                                                     ` Takashi Yano
2021-09-01  8:03                                                       ` Corinna Vinschen
2021-09-01  8:13                                                         ` Corinna Vinschen
2021-08-30 13:36                               ` Ken Brown
2021-08-30 14:05                                 ` Corinna Vinschen
2021-08-30 15:53                                   ` Corinna Vinschen
2021-08-30 17:00                                     ` Corinna Vinschen
2021-08-30 17:11                                       ` Corinna Vinschen
2021-08-30 18:59                                       ` Ken Brown
2021-08-30 19:12                                         ` Ken Brown
2021-08-30 20:21                                         ` Corinna Vinschen
2021-08-30 20:14                                       ` Corinna Vinschen
2021-08-30 20:47                                         ` Ken Brown
2021-08-31  8:55                                         ` Takashi Yano
2021-08-31  9:08                                           ` Corinna Vinschen
2021-08-31  9:25                                             ` Takashi Yano
2021-08-31 10:05                                               ` Corinna Vinschen
2021-08-31 10:18                                                 ` Corinna Vinschen
2021-08-31 11:45                                                   ` Takashi Yano
2021-08-31 12:31                                                     ` Takashi Yano
2021-08-31 15:08                                                       ` Corinna Vinschen
2021-08-31 12:33                                                     ` Ken Brown
2021-08-31 15:18                                                       ` Corinna Vinschen
2021-08-31 15:27                                                         ` Corinna Vinschen
2021-08-31 15:50                                                           ` Corinna Vinschen
2021-08-31 16:19                                                             ` Ken Brown
2021-08-31 16:38                                                               ` Ken Brown
2021-08-31 17:30                                                                 ` Corinna Vinschen
2021-08-31 18:54                                                                   ` Ken Brown
2021-08-31 19:51                                                                     ` Corinna Vinschen
2021-08-31 23:02                                                             ` Takashi Yano
2021-09-01  0:16                                                               ` Takashi Yano
2021-09-01  8:07                                                                 ` Corinna Vinschen
2021-09-01  8:23                                                                   ` Takashi Yano
2021-09-01  8:46                                                                     ` Corinna Vinschen
2021-09-01 12:56                                                                       ` Ken Brown
2021-09-01 13:52                                                                         ` Corinna Vinschen
2021-09-01 23:02                                                                           ` Ken Brown
2021-09-02  8:17                                                                             ` Corinna Vinschen
2021-09-02 13:01                                                                               ` Ken Brown
2021-09-02 19:00                                                                                 ` Corinna Vinschen
2021-09-02 19:34                                                                                   ` Ken Brown
2021-09-02 19:35                                                                                   ` Corinna Vinschen
2021-09-02 20:19                                                                                     ` Ken Brown
2021-09-03  9:12                                                                                       ` Corinna Vinschen
2021-09-03 19:00                                                                                         ` Ken Brown
2021-09-03 19:53                                                                                           ` Ken Brown
2021-09-03 19:54                                                                                           ` Corinna Vinschen
2021-09-03 20:05                                                                                             ` Ken Brown
2021-09-03 10:00                                                                                     ` Takashi Yano
2021-09-03 10:13                                                                                       ` Takashi Yano
2021-09-03 11:31                                                                                         ` Corinna Vinschen
2021-09-03 11:41                                                                                           ` Corinna Vinschen
2021-09-03 12:13                                                                                             ` Ken Brown
2021-09-03 15:00                                                                                               ` Corinna Vinschen
2021-09-03 15:14                                                                                                 ` Ken Brown
2021-09-03 15:17                                                                                                   ` Corinna Vinschen
2021-09-03 12:22                                                                                             ` Takashi Yano
2021-09-03 13:27                                                                                               ` Ken Brown
2021-09-03 15:37                                                                                               ` Corinna Vinschen
2021-09-04 12:02                                                                                                 ` Takashi Yano
2021-09-04 12:37                                                                                                   ` Takashi Yano
2021-09-04 14:04                                                                                                     ` Ken Brown
2021-09-04 23:15                                                                                                       ` Takashi Yano
2021-09-05 13:40                                                                                                         ` Takashi Yano
2021-09-05 13:50                                                                                                           ` Takashi Yano [this message]
2021-09-05 18:47                                                                                                             ` Ken Brown
2021-09-05 19:42                                                                                                               ` Takashi Yano
2021-09-05 20:09                                                                                                               ` Takashi Yano
2021-09-05 20:27                                                                                                                 ` Ken Brown
2021-09-06  8:13                                                                                                                 ` Corinna Vinschen
2021-09-06 11:16                                                                                                                   ` Takashi Yano
2021-09-06 12:49                                                                                                                     ` Corinna Vinschen
2021-09-06 13:16                                                                                                                       ` Takashi Yano
2021-09-06 16:08                                                                                                                         ` Corinna Vinschen
2021-09-06 23:39                                                                                                                           ` Takashi Yano
2021-09-07  9:14                                                                                                                             ` Corinna Vinschen
2021-09-07 11:03                                                                                                                               ` Takashi Yano
2021-09-07 16:14                                                                                                                       ` Ken Brown
2021-09-07 18:26                                                                                                                         ` Corinna Vinschen
2021-09-03 10:38                                                                                       ` Takashi Yano
2021-09-08 11:32                                                                                     ` Takashi Yano
2021-09-08 11:55                                                                                       ` Corinna Vinschen
2021-09-08 12:33                                                                                         ` Takashi Yano
2021-09-08 17:43                                                                                         ` Ken Brown
2021-09-08 18:28                                                                                           ` Corinna Vinschen
2021-09-02  8:15                                                                       ` Takashi Yano
2021-09-02 18:54                                                                         ` Corinna Vinschen
2021-09-07  3:26             ` Takashi Yano
2021-09-07 10:50               ` Takashi Yano
2021-09-08  0:07                 ` Takashi Yano
2021-09-08  4:11                   ` Takashi Yano
2021-09-08  9:01                     ` Takashi Yano
2021-09-08  9:01                     ` Corinna Vinschen
2021-09-08  9:26                       ` Corinna Vinschen
2021-09-08  9:45                         ` Takashi Yano
2021-09-08 10:04                           ` Corinna Vinschen
2021-09-08 10:45                             ` Takashi Yano
2021-09-08 10:51                               ` Corinna Vinschen
2021-09-09  3:21                                 ` Takashi Yano
2021-09-09  9:37                                   ` Corinna Vinschen
2021-09-09 10:55                                     ` Takashi Yano
2021-09-09 11:41                                       ` Corinna Vinschen
2021-09-08  9:37                       ` Takashi Yano
2021-09-09  3:41               ` Takashi Yano
2021-09-09  8:05                 ` Takashi Yano
2021-09-09 12:19                   ` Takashi Yano
2021-09-09 12:42                     ` Takashi Yano
2021-09-09 21:53                       ` Takashi Yano
2021-09-10  3:41                         ` Takashi Yano
2021-09-10 10:57                       ` Ken Brown
2021-09-10 15:17                         ` Ken Brown
2021-09-10 15:26                           ` Corinna Vinschen
2021-09-10 22:57                           ` Takashi Yano
2021-09-11  2:17                             ` Ken Brown
2021-09-11  2:35                               ` Takashi Yano
2021-09-11 13:12                                 ` Ken Brown
2021-09-12  6:23                                   ` Takashi Yano
2021-09-12 14:39                                     ` Ken Brown
2021-09-13  9:11                                       ` Corinna Vinschen
2021-09-13 12:30                                         ` Ken Brown
2021-09-12  8:48                                   ` Takashi Yano
2021-09-12 11:04                                     ` Takashi Yano
2021-09-12 15:10                                       ` Ken Brown
2021-09-12 21:46                                         ` Ken Brown
2021-09-12 23:54                                           ` Takashi Yano
2021-09-13  2:19                                             ` Ken Brown
2021-09-13  8:40                                             ` Takashi Yano
2021-09-13 12:51                                               ` Ken Brown
2021-09-13 17:05                                                 ` Ken Brown
2021-09-13  9:42                                           ` Corinna Vinschen
2021-09-13 13:03                                             ` Ken Brown
2021-09-13 18:39                                               ` Takashi Yano
2021-09-12 23:41                                         ` Takashi Yano
2021-09-13 17:42                                       ` Ken Brown
2021-09-13 18:54                                         ` Takashi Yano
2021-09-13 18:32                                       ` Corinna Vinschen
2021-09-13 19:37                                         ` Takashi Yano
2021-09-13 20:15                                           ` Corinna Vinschen
2021-09-14  8:07                                             ` Takashi Yano
2021-09-14  8:47                                               ` Corinna Vinschen
2021-09-14 12:38                                                 ` Ken Brown
2021-09-14 14:15                                                   ` Corinna Vinschen
2021-09-14  8:08                                           ` Takashi Yano
2021-09-14  9:03                                             ` Corinna Vinschen
2021-09-14  9:56                                               ` Takashi Yano
2021-09-14 10:19                                                 ` Takashi Yano
2021-09-14 11:03                                                   ` Corinna Vinschen
2021-09-14 12:05                                                     ` Takashi Yano
2021-09-14 14:17                                                       ` Corinna Vinschen
2021-09-14 22:14                                                       ` Ken Brown
2021-09-15  0:21                                                         ` Takashi Yano
2021-09-15  0:44                                                           ` Takashi Yano
2021-09-15  0:59                                                             ` Takashi Yano
2021-09-15  9:57                                                               ` Corinna Vinschen
2021-09-15 10:48                                                                 ` Takashi Yano
2021-09-15 10:58                                                                   ` Takashi Yano
2021-09-15 11:34                                                                     ` Corinna Vinschen
2021-09-15 11:40                                                                       ` Corinna Vinschen
2021-09-15 11:13                                                                   ` Corinna Vinschen
2021-09-15 11:41                                                                     ` Ken Brown
2021-09-15 11:49                                                                       ` Corinna Vinschen
2021-09-15 11:54                                                                     ` Takashi Yano
2021-09-15 12:20                                                                       ` Corinna Vinschen
2021-09-15 13:04                                                                         ` Takashi Yano
2021-09-15 13:42                                                                           ` Corinna Vinschen
2021-09-15 16:22                                                                             ` Ken Brown
2021-09-15 17:09                                                                               ` Ken Brown
2021-09-16  0:22                                                                                 ` Takashi Yano
2021-09-16  2:28                                                                                   ` Ken Brown
2021-09-16  9:09                                                                                 ` Takashi Yano
2021-09-16 13:02                                                                                   ` Takashi Yano
2021-09-16 13:25                                                                                     ` Corinna Vinschen
2021-09-16 14:27                                                                                       ` Takashi Yano
2021-09-16 15:01                                                                                         ` Corinna Vinschen
2021-09-16 15:46                                                                                           ` Ken Brown
2021-09-16 16:02                                                                                             ` Ken Brown
2021-09-16 19:42                                                                                               ` Takashi Yano
2021-09-16 20:28                                                                                                 ` Ken Brown
2021-09-16 19:48                                                                                               ` Ken Brown
2021-09-16 20:01                                                                                                 ` Takashi Yano
2021-09-17  2:25                                                                                                   ` Ken Brown
2021-09-17  8:31                                                                                                     ` Takashi Yano
2021-09-17 11:16                                                                                                       ` Ken Brown
2021-09-17 16:23                                                                                                         ` Takashi Yano
2021-09-17 17:08                                                                                                           ` Ken Brown
2021-09-17 17:39                                                                                                             ` Jon Turney
2021-09-17 17:43                                                                                                             ` Takashi Yano
2021-09-17 19:53                                                                                                               ` Ken Brown
2021-09-18  1:30                                                                                                                 ` Takashi Yano
2021-09-18  2:07                                                                                                                   ` Ken Brown
2021-09-18  2:10                                                                                                                     ` Ken Brown
2021-09-18  8:03                                                                                                                       ` Takashi Yano
2021-09-18 11:12                                                                                                                         ` Ken Brown
2021-09-18 11:35                                                                                                                           ` Takashi Yano
2021-09-18 14:11                                                                                                                             ` Jon Turney
2021-09-18 13:44                                                                                           ` Ken Brown
2021-09-19  1:31                                                                                             ` Takashi Yano
2021-09-19 14:35                                                                                               ` Ken Brown
2021-09-20  9:29                                                                                                 ` Takashi Yano
2021-09-16  0:13                                                                               ` Takashi Yano
2021-09-16  2:26                                                                                 ` Ken Brown
2021-09-13  9:07                                 ` Corinna Vinschen
2021-09-20 12:52                                   ` Takashi Yano
2021-09-20 19:14                                     ` Ken Brown
2021-09-20 21:09                                       ` Ken Brown
2021-09-20 21:21                                         ` Ken Brown
2021-09-20 21:27                                         ` Takashi Yano
2021-09-20 21:39                                           ` Ken Brown
2021-09-20 22:16                                             ` Takashi Yano
2021-09-20 22:46                                               ` Ken Brown
2021-09-20 22:50                                                 ` Ken Brown
2021-09-20 23:22                                                   ` Takashi Yano
2021-09-21  8:30                                                     ` Takashi Yano
2021-09-21  9:26                                                       ` Mark Geisert
2021-09-21 10:10                                                         ` Takashi Yano
2021-09-21 21:10                                                           ` Mark Geisert
2021-09-21 13:31                                                       ` Ken Brown
2021-09-21 15:36                                                         ` Takashi Yano
2021-09-21 18:51                                                           ` Ken Brown
2021-09-23  8:26                                                             ` Takashi Yano
2021-09-23 13:03                                                               ` Ken Brown
2021-09-23 15:03                                                                 ` Takashi Yano
2021-09-23 16:29                                                                   ` Ken Brown
2021-10-18 10:51                                                                   ` Corinna Vinschen
2021-10-18 12:02                                                                     ` Takashi Yano

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