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From: Achim Gratz <Stromeko AT nexgo DOT de>
To: cygwin AT cygwin DOT com
Subject: Re: Cygwin multithreading performance
References: <CABPLASTtRK4mNxh0M_AnZgjJQ15kWPx+L=U=VCU3Wwi7jV_57A AT mail DOT gmail DOT com>
Date: Fri, 18 Dec 2015 16:06:45 +0100
In-Reply-To: <CABPLASTtRK4mNxh0M_AnZgjJQ15kWPx+L=U=VCU3Wwi7jV_57A@mail.gmail.com>	(Kacper Michajlow's message of "Sat, 14 Nov 2015 01:24:18 +0100")
Message-ID: <87bn9nhk3e.fsf@Rainer.invalid>
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Kacper Michajlow writes:
> I recently noticed that Cygwin multithreading is very inefficient. I
> was repacking few git repositories and with Cygwin's git, it spawns
> threads but they are so badly synchronized that there is no speed gain
> over one thread and possible loose because of the overhead. On my
> machine I got 7-10% CPU usage while with git build with mingw easily
> uses 100%.

I've been testing this again with my local copy of Emacs' Git repository
and at least on this two-core system it works just fine (it was working
fine on a four-core system earlier).  The object count phase looks
serialized and doesn't go over 50%, however a good deal of that is
system time anyway, so I assume it's file access.  The actual
compression uses whatever CPU it can get, with the occasional spike in
system time when it goes to disk (it's an SSD).

Is your repo local or on some remote filesystem?


Regards,
Achim.
-- 
+<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+

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