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([2a01:599:915:8911:b13f:d972:e237:7fe2]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-441b8a285c2sm171119875e9.32.2025.05.06.07.36.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 06 May 2025 07:36:25 -0700 (PDT) Message-ID: Date: Tue, 6 May 2025 16:36:23 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] Re: [PATCH v3 3/6] mm: shmem: add large folio support for tmpfs To: Baolin Wang , Daniel Gomez Cc: =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , akpm@linux-foundation.org, hughd@google.com, willy@infradead.org, wangkefeng.wang@huawei.com, 21cnbao@gmail.com, ryan.roberts@arm.com, ioworker0@gmail.com, da.gomez@samsung.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, regressions@lists.linux.dev, intel-gfx@lists.freedesktop.org, Eero Tamminen References: <035bf55fbdebeff65f5cb2cdb9907b7d632c3228.1732779148.git.baolin.wang@linux.alibaba.com> <57dc4929-268b-4f3f-a0f8-43d6ec85974f@linux.alibaba.com> <72978e3a-ee67-47d4-b06d-e911bc5d57ff@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 3E9E940009 X-Stat-Signature: ycqxk37msfdrqrudau79ay4bxz4s9bj6 X-Rspam-User: X-HE-Tag: 1746542190-445364 X-HE-Meta: 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 Iu+XPVV4 8BcBYOuHCTgKZ12yk+PX1FrUCTlTMVWaHZnm/cAThDpd2DvMlkDDQezBy/S3wTkdH3e8eF8exlIwUc0gxAtTlFtkDeMccg8yETXUkXxOuGW0rlBGFO+MOkNwAA+xjVMnzNtyQXt2bhLA6FrTr1Advz+n+mkc+F/rtw5B+XblzVcNPE4uMjmBScbdJ98Slu4v/agkVvF5GRoJN4FNBOpL6TkQp+jp8AfKs9Rs9MRxwyNJ+wxNYQE0tHxZp3MXvDSuJO8PhwCjU8hNg7VPOQ6+zIZDebCQ9iyzzJF+xn/zteaUxBCS45+k8332e9kcV9vzT28ZMfDXth1w5c3o7ZLlfTJ/rRTsWzwd8mUJTXWR46sy44A+4z1fM2GMVhqbvfaQIGCwjHDhA+ddgPqOFbTfb1nwu4JJaAlfTJKQYAxhrcCkzLzLS7esoUQyFgto3MIQIYntiaWzXG8cOnlVUKjdmXcgMRC+nfPal3JUTYQJBz8HAQrs= 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 06.05.25 05:33, Baolin Wang wrote: > > > On 2025/5/2 23:31, David Hildenbrand wrote: >> On 02.05.25 15:10, Daniel Gomez wrote: >>> On Fri, May 02, 2025 at 09:18:41AM +0100, David Hildenbrand wrote: >>>> On 02.05.25 03:02, Baolin Wang wrote: >>>>> >>>>> >>>>> On 2025/4/30 21:24, Daniel Gomez wrote: >>>>>> On Wed, Apr 30, 2025 at 02:20:02PM +0100, Ville Syrjälä wrote: >>>>>>> On Wed, Apr 30, 2025 at 02:32:39PM +0800, Baolin Wang wrote: >>>>>>>> On 2025/4/30 01:44, Ville Syrjälä wrote: >>>>>>>>> On Thu, Nov 28, 2024 at 03:40:41PM +0800, Baolin Wang wrote: >>>>>>>>> Hi, >>>>>>>>> >>>>>>>>> This causes a huge regression in Intel iGPU texturing performance. >>>>>>>> >>>>>>>> Unfortunately, I don't have such platform to test it. >>>>>>>> >>>>>>>>> >>>>>>>>> I haven't had time to look at this in detail, but presumably the >>>>>>>>> problem is that we're no longer getting huge pages from our >>>>>>>>> private tmpfs mount (done in i915_gemfs_init()). >>>>>>>> >>>>>>>> IIUC, the i915 driver still limits the maximum write size to >>>>>>>> PAGE_SIZE >>>>>>>> in the shmem_pwrite(), >>>>>>> >>>>>>> pwrite is just one random way to write to objects, and probably >>>>>>> not something that's even used by current Mesa. >>>>>>> >>>>>>>> which prevents tmpfs from allocating large >>>>>>>> folios. As mentioned in the comments below, tmpfs like other file >>>>>>>> systems that support large folios, will allow getting a highest >>>>>>>> order >>>>>>>> hint based on the size of the write and fallocate paths, and then >>>>>>>> will >>>>>>>> attempt each allowable huge order. >>>>>>>> >>>>>>>> Therefore, I think the shmem_pwrite() function should be changed to >>>>>>>> remove the limitation that the write size cannot exceed PAGE_SIZE. >>>>>> >>>>>> To enable mTHP on tmpfs, the necessary knobs must first be enabled >>>>>> in sysfs >>>>>> as they are not enabled by default IIRC (only THP, PMD level). >>>>>> Ville, I >>>>>> see i915_gemfs the huge=within_size mount option is passed. Can you >>>>>> confirm >>>>>> if /sys/kernel/mm/transparent_hugepage/hugepages-*/enabled are also >>>>>> marked as >>>>>> 'always' when the regression is found? >>>>> >>>>> The tmpfs mount will not be controlled by >>>>> '/sys/kernel/mm/transparent_hugepage/hugepages-*Kb/enabled' (except for >>>>> the debugging options 'deny' and 'force'). >>>> >>>> Right, IIRC as requested by Willy, it should behave like other FSes >>>> where >>>> there is no control over the folio size to be used. >>> >>> Thanks for reminding me. I forgot we finally changed it. >>> >>> Could the performance drop be due to the driver no longer using >>> PMD-level pages? >> >> I suspect that the faulting logic will now go to a smaller order first, >> indeed. >> >> ... trying to digest shmem_allowable_huge_orders() and >> shmem_huge_global_enabled(), having a hard time trying to isolate the >> tmpfs case: especially, if we run here into the vma vs. !vma case. >> >> Without a VMA, I think we should have "mpfs will allow getting a highest >> order hint based on and fallocate paths, then will try each allowable >> order". >> >> With a VMA (no access hint), "we still use PMD-sized order to locate >> huge pages due to lack of a write size hint." >> >> So if we get a fallocate()/write() that is, say, 1 MiB, we'd now >> allocate an 1 MiB folio instead of a 2 MiB one. > > Right. > > So I asked Ville how the shmem folios are allocated in the i915 driver, > and to see if we can make some improvements. Maybe preallocation (using fallocate) might be reasonable for their use case: if they know they will consume all that memory either way. If it's sparse, it's more problematic. -- Cheers, David / dhildenb