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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190116124431.GK24149@dhcp22.suse.cz> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190116_052726_409733_BB99A14F X-CRM114-Status: GOOD ( 15.98 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, linux-sh@vger.kernel.org, peterz@infradead.org, catalin.marinas@arm.com, dave.hansen@linux.intel.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, kvmarm@lists.cs.columbia.edu, mpe@ellerman.id.au, linux@armlinux.org.uk, mingo@redhat.com, vbabka@suse.cz, rientjes@google.com, palmer@sifive.com, greentime@andestech.com, marc.zyngier@arm.com, rppt@linux.vnet.ibm.com, shakeelb@google.com, kirill@shutemov.name, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, ard.biesheuvel@linaro.org, robin.murphy@arm.com, steve.capper@arm.com, christoffer.dall@arm.com, james.morse@arm.com, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 01/16/2019 06:14 PM, Michal Hocko wrote: > On Wed 16-01-19 04:30:18, Matthew Wilcox wrote: >> On Wed, Jan 16, 2019 at 07:57:03AM +0100, Michal Hocko wrote: >>> On Wed 16-01-19 11:51:32, Anshuman Khandual wrote: >>>> All architectures have been defining their own PGALLOC_GFP as (GFP_KERNEL | >>>> __GFP_ZERO) and using it for allocating page table pages. This causes some >>>> code duplication which can be easily avoided. GFP_KERNEL allocated and >>>> cleared out pages (__GFP_ZERO) are required for page tables on any given >>>> architecture. This creates a new generic GFP flag flag which can be used >>>> for any page table page allocation. Does not cause any functional change. >>>> >>>> GFP_PGTABLE is being added into include/asm-generic/pgtable.h which is the >>>> generic page tabe header just to prevent it's potential misuse as a general >>>> allocation flag if included in include/linux/gfp.h. >>> >>> I haven't reviewed the patch yet but I am wondering whether this is >>> really worth it without going all the way down to unify the common code >>> and remove much more code duplication. Or is this not possible for some >>> reason? >> >> Exactly what I suggested doing in response to v1. >> >> Also, the approach taken here is crazy. x86 has a feature that no other >> architecture has bothered to implement yet -- accounting page tables >> to the process. Yet instead of spreading that goodness to all other >> architectures, Anshuman has gone to more effort to avoid doing that. > > Yes, I believe the only reason this is x86 only is that each arch would > have to be tweaked separately. So a cleanup in _that_ regard would be > helpful. There is no real reason to have ptes accounted only for x86. > There might be some exceptions but well, our asm-generic allows to opt > in for generic implementation or override it with a special one. The > later should be an exception rather than the rule. Fair enough. So we seem to have agreement over __GFP_ACCOUNT for user page tables but not for the kernel. But should we accommodate __GFP_RETRY_MAYFAIL or drop them altogether (including multi order allocation requests) ? _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel