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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rQYmh-0000000323y-3WgP; Thu, 18 Jan 2024 20:14:43 +0000 Date: Thu, 18 Jan 2024 20:14:43 +0000 From: Matthew Wilcox To: Yang Shi Cc: jirislaby@kernel.org, surenb@google.com, riel@surriel.com, cl@linux.com, akpm@linux-foundation.org, yang@os.amperecomputing.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: huge_memory: don't force huge page alignment on 32 bit Message-ID: References: <20240118133504.2910955-1-shy828301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240118133504.2910955-1-shy828301@gmail.com> X-Rspam-User: X-Stat-Signature: of9j7m6yam1z5x1zc1x8ngjte9fgp1kz X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 643FC8000E X-HE-Tag: 1705608894-813246 X-HE-Meta: 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 agOx3fAj /FxsTHSCR1xqc+OkuFfF0EYCD35QJtM5DLZ0jd3ewMxvurr19ZD30p7YKpr1SoiNqigT/G2Kn9lIjslVH67TtgTIvLkZ1Ku0802dXh9gYR/Bls9y8a9ksR1y1YvOCXi8uWgY9l62gTYDUG++3hSg3T3CVzZ+1SRjlaUisRx1MchMbB6Ata1Qh3hdzWfU3SXZwD2EznIV47reh0mjCSAdvmyahr5EVlYm1gbhkUKWi/vmaT9lKrvaaBPkQnbZJU0H/6/aliXzZCaKfmVMBsd2o8xcvz50oH+i5jWYwWZxeIKdVyN4KNmuzo95ibg== 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: On Thu, Jan 18, 2024 at 05:35:04AM -0800, Yang Shi wrote: > It doesn't make too much sense to force huge page alignment on 32 bit > system due to the constrained virtual address space. > > [1] https://lore.kernel.org/linux-mm/CAHbLzkqa1SCBA10yjWTtA2mKCsoK5+M1BthSDL8ROvUq2XxZMw@mail.gmail.com/T/#mf211643a0427f8d6495b5b53f8132f453d60ab95 > [2] https://lore.kernel.org/linux-mm/CAHbLzkqa1SCBA10yjWTtA2mKCsoK5+M1BthSDL8ROvUq2XxZMw@mail.gmail.com/T/#me93dff2ccbd9902c3e395e1c022fb454e48ecb1d I feel sure there are shorter URLs for those messages ... > @@ -811,6 +812,14 @@ static unsigned long __thp_get_unmapped_area(struct file *filp, > loff_t off_align = round_up(off, size); > unsigned long len_pad, ret; > > + /* > + * It doesn't make too much sense to froce huge page alignment on > + * 32 bit system or compat userspace due to the contrained virtual > + * address space and address entropy. > + */ I honestly wouldn't even comment this. But if you must, /* Using THP alignment is not as important as address randomisation */ > + if (IS_ENABLED(CONFIG_32BIT) || in_compat_syscall()) > + return 0; > + > if (off_end <= off_align || (off_end - off_align) < size) > return 0; > > -- > 2.41.0 >