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Wed, 30 Jul 2025 17:20:36 +0800 From: Zhang Qilong To: , CC: , , , , , , Zhang Qilong Subject: [PATCH resend v2] /dev/zero: try to align PMD_SIZE for private mapping Date: Wed, 30 Jul 2025 17:19:05 +0800 Message-ID: <20250730091905.383353-1-zhangqilong3@huawei.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.175.124.71] X-ClientProxiedBy: kwepems100001.china.huawei.com (7.221.188.238) To dggpemf500012.china.huawei.com (7.185.36.8) X-Rspam-User: X-Rspamd-Queue-Id: 1E65E1C0006 X-Rspamd-Server: rspam06 X-Stat-Signature: ncz5zcczf4ty4yfn3fggrhefxauosi87 X-HE-Tag: 1753867242-327529 X-HE-Meta: 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 gpspewfq Rp+EFfPs4YgEhrPydXQnVuHPnLukq72rdhIs12lEhoQ3lOEEqxAz8tolpul+sBdlZCRwyrtz7NY0OnoXfkfGfQ2xvofpkmPeBRGxBK9f0cLuQJAYMOOxTqhUTejFI09wcuXC5pzGLo89AEFzbxIcja4Fk3Sm3fBNNJtG7O5Cs2NP6nUxTmsl6Gz9+teY7gS0T9KcWujVDeLe6E4tT9HQFealUAlTMv3z8P2XCxy00rDYshAs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Attempt to map aligned to huge page size for private mapping which could achieve performance gains, the mprot_tw4m in libMicro average execution time on arm64: - Test case: mprot_tw4m - Before the patch: 22 us - After the patch: 17 us Signed-off-by: Zhang Qilong --- v2: - Add comments on code suggested by Lorenzo - Use IS_ENABLED to check THP config drivers/char/mem.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 48839958b0b1..c27cc89bd02d 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -525,11 +525,18 @@ static unsigned long get_unmapped_area_zero(struct file *file, * so as not to confuse shmem with our handle on "/dev/zero". */ return shmem_get_unmapped_area(NULL, addr, len, pgoff, flags); } - /* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */ + /* + * Otherwise flags & MAP_PRIVATE: with no shmem object beneath it, + * attempt to map aligned to huge page size if possible, otherwise we + * fall back to system page size mappings. + */ + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) + return thp_get_unmapped_area(file, addr, len, pgoff, flags); + return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags); #else return -ENOSYS; #endif } -- 2.43.0