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Date:      Sat, 8 Jan 2011 19:00:16 +0800
From:      Denny Lin <dennylin93@hs.ntnu.edu.tw>
To:        Volodymyr Kostyrko <c.kworr@gmail.com>
Cc:        Anonymous <swell.k@gmail.com>, freebsd-ports@freebsd.org
Subject:   Re: Ccache hangs while compiling and cache size is exaggerated
Message-ID:  <20110108110016.GA72486@mail.hs.ntnu.edu.tw>
In-Reply-To: <4D228490.9080602@gmail.com>
References:  <20110102113714.GA81113@mail.hs.ntnu.edu.tw> <868vz34d76.fsf@gmail.com> <4D228490.9080602@gmail.com>

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On Tue, Jan 04, 2011 at 04:23:12AM +0200, Volodymyr Kostyrko wrote:
> 02.01.2011 16:01, Anonymous wrote:
> >>I'm using ccache 3.1.3, and it often hangs while compiling.
> >
> >What its waiting channel? Hit ^T when it hangs or run under ktrace(1).

This is what appears when I hit ^T:
load: 0.96  cmd: ccache 25893 [zio->io_cv)] 3.83r 0.00u 0.06s 1% 1604k

> Not just every compilation attempt triggers it. Chances are closer to 100/1.

Correct, but it's always triggered at the same point.

> >>Every time this happens, the cache size from $ ccache -s also becomes
> >>ridiculously large (larger than the actual cache size).
> >>
> >>$ ccache -s
> >>[...]
> >>cache size    6.9 Gbytes
> >
> >>The filesystem says it's only 2.9 GB.
> >
> >How did you measure it? du(1) with `-A' option?
> >For example, compression can make difference

Compression is turned off.

> I'd clarify this one. ccache reports size of cache +4G per damaged 
> subdir. If damaged subdir would be removed ccache reports normal size of 
> cache again.
> 
> >>I can reproduce this, but I don't know what is causing this.
> 
> This gives high IO. When ccache thinks cache is full it tries to purge 
> it, yet purge does nothing. But this means walking all subdir per each 
> compilation.

This seems to be the exact reason ccache is hanging. Does anyone have a
clue why subdirs are getting damaged and how this can be prevented?

-- 
Denny Lin



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