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b=Z8FK0e7SPnAM3cMF0w014gX4GuKSlBh8apadUkxqyGsIzVHPTST9mgaXfhe27wQua yZV5XioxuYwjTVaoB87wb9qtpYI5/IqlA2kFn5PAHJYjyxBNLPjv/iBBmlmPhHoPr+ HcoT7dnd5MR5IE12J2+9FDd4KgN49UXYJQ4s2T8U= Date: Tue, 11 Feb 2025 15:50:16 -0800 From: Andrew Morton To: I Hsin Cheng Cc: zhengqi.arch@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jserv@ccns.ncku.edu.tw Subject: Re: [PATCH] mm: pgtable: Unlock pml without branches when !start_pte Message-Id: <20250211155016.857387cd35e19a463d779cae@linux-foundation.org> In-Reply-To: References: <20250210100948.312130-1-richard120310@gmail.com> <20250210163736.ed1c93a44a47e39820fb8d85@linux-foundation.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 329E0140006 X-Rspamd-Server: rspam07 X-Stat-Signature: yadxjkruoszgwhnqtio8yt43ozhstzbe X-HE-Tag: 1739317818-728889 X-HE-Meta: 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 v3RNjhmA KqEiN8xlYQxdl4GW/r6zkL1IadCAaY7UNJwLeBWOlab6xc/NfEPkBjxAtynNh3UT3yU90/x0lPB1P1GGekOHkgpZVa+X+7E+wjGIVx3Cld8hU+zhpdrw5M0r38+j19DNOSwOdWyIgJnEqszdU24UcEU4wXN42i0j2QmdFbHJFZrbqGr2rKOBBwJJZrr0AbKCkmQQg+7vhuFjmiykSiMtQb+iprO2FMWqEWyW0IhkwIW6vzFGwbDWuGDDFaxtLESJtJ2TL4mDX8IeuC0fUd9C7gVxJvng8Oe0V9X+01AGvbI5xfBsnwmBcj0j+2xKINDZb6LjrbNTCcM5IqGQ3F+n53fbc7CmQmHrywj1IDP8tr7FOXcU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000032, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 11 Feb 2025 14:49:47 +0800 I Hsin Cheng wrote: > > if (ptl != pml) > > +out_unlock: > > spin_unlock(pml); > > } > > _ > > > > but that's really ugly. > > I agree. Would you be so nice to suggest some test method for me so I > can try to test how much benefit we can get from this? > > If the case happens frequently enough I think it might be worth it? I expect this error patch is basically never taken - put a printk in there and run some tests?