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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qfmKb-002bfo-3g; Mon, 11 Sep 2023 19:12:21 +0000 Date: Mon, 11 Sep 2023 20:12:21 +0100 From: Matthew Wilcox To: Dave Hansen Cc: Yin Fengwei , syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] BUG: Bad page map (7) Message-ID: References: <000000000000d099fa0604f03351@google.com> <0465d13d-83b6-163d-438d-065d03e9ba76@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 6AB821A0007 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 9uxdfccnr5drehq63q3attakbrd4sdqj X-HE-Tag: 1694459554-975777 X-HE-Meta: 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 rh3ofRS2 jUYLhUlJB2UvrgnSCdkaDLPHKLWD8TTEb7NxfNBFJdU95oObzHcvk8+5xyMB+R9QlNd9iue/TeeLw07Yz0xFXJxnyr/gXJfE1m0S96+/ZgA3R8yBoCR98KCw5oCeHfosQ6bsvi9c9k1rFKo/pngvC8MV8u8UTBFAoyB6mdFkn9J4QL3GLnHm7uHnWq1Bejd+E6nq0lVsumX3K0Rb0nNSzq1IYD/WFYqgPXf19IgYaKQ1I1reamQUsb4bojPkdIOZgR0N8YKcPF2H06iVDd0Bdmebkxg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.048638, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Sep 11, 2023 at 09:55:37AM -0700, Dave Hansen wrote: > On 9/11/23 09:44, Matthew Wilcox wrote: > > After fixing your two typos, this assembles to 176 bytes more code than > > my version. Not sure that's great. > > Maybe I'm a fool, but 176 bytes of text bloat isn't scaring me off too > much. I'd much rather have that than another window into x86 goofiness > to maintain. > > Does that 176 bytes translate into meaningful performance, or is it just > a bunch of register bit twiddling that the CPU will sail through? I'm ... not sure how to tell. It's 1120 bytes vs 944 bytes and crawling through that much x86 assembly isn't my idea of a great time. I can send you objdump -dr for all three options if you like? Maybe there's a quick way to compare them that I've never known about.