linux-kernel - RE: [PATCH] /dev/zero: also implement ->read

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Message-ID: <f09599c8e85940a6b34877854df241f8@AcuMS.aculab.com>
Date:   Mon, 7 Sep 2020 08:18:13 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christophe Leroy' <christophe.leroy@...roup.eu>,
        Pavel Machek <pavel@...x.de>
CC:     Christoph Hellwig <hch@....de>, "arnd@...db.de" <arnd@...db.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] /dev/zero: also implement ->read

From: Christophe Leroy
> Sent: 07 September 2020 05:44
...
> If you are talking about the tests around the set_fs series from
> Christoph, I identified that the degradation was linked to
> CONFIG_STACKPROTECTOR_STRONG being selected by default, which provides
> unreliable results from one patch to another, GCC doing some strange
> things linked to unrelated changes.
> 
> With CONFIG_STACKPROTECTOR set to N, I get stable performance and no
> degradation with any of the patches of the set_fs series.

Ah I didn't spot that response going through.

Sounds like that option should be disabled if it causes that
much of a performance drop.

	David

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