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Thu, 18 Apr 2024 09:47:36 +0800 Message-ID: <20cbfcce-fc02-4af2-a342-82bd4359e977@huawei.com> Date: Thu, 18 Apr 2024 09:47:35 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: memory: check userfaultfd_wp() in vmf_orig_pte_uffd_wp() Content-Language: en-US To: Peter Xu CC: Andrew Morton , References: <20240417082359.3413259-1-wangkefeng.wang@huawei.com> From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm100001.china.huawei.com (7.185.36.93) X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 17BDBC001C X-Stat-Signature: iiae8c9yff4ux4bt3soyu61czqp3mdp8 X-Rspam-User: X-HE-Tag: 1713404860-366865 X-HE-Meta: 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 MUmubN9x VlHjFKw6biP1pfRDjsu/ArngQnORE+bKAAdUwAdQrM0lQ//o1tUdQH+bhfeTRXnwoKoOMK2Ct36p90ZE1aTKHzOYqG4iKvax5F7iKp4kPnSepWMUFuncT1HArO5Aa4u8pNE9tgJzPDDJm4glZXBLSsVLkUisqN68o+jlSP2HOyDQ/rbgiVROQ07UOeQAZACiEDCV97g9Tle+N2Zj4Fet+56AgvxagVMtclxt7R1kthqgffAg= 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 2024/4/18 2:34, Peter Xu wrote: > Hi, Kefeng, > > On Wed, Apr 17, 2024 at 05:30:40PM +0800, Kefeng Wang wrote: >> >> >> On 2024/4/17 16:23, Kefeng Wang wrote: >>> Directly call vmf_orig_pte_uffd_wp() in do_anonymous_page() and >>> set_pte_range() to save a uffd_wp and add userfaultfd_wp() check >>> in vmf_orig_pte_uffd_wp() to avoid the unnecessary function calls >>> in the most sense, lat_pagefault testcase does show improvement >>> though very small(~1%). > > I'm ok with the change if that helps as big as 1%, but I'm a bit surprised > to see such a difference, because for file pte_marker_uffd_wp() should > check first on pte_none() then it should return already if uffd not even > registered for the vma, while orig_pte should be hot too if valid. Yes, retest, not as big as 1%, but the perf shows vmf_orig_pte_uffd_wp is eliminated, [root@localhost]# perf report -i perf.data.old |grep vmf 0.17% 0.13% lat_pagefault [kernel.kallsyms] [k] vmf_orig_pte_uffd_wp.part.0.isra.0 [root@localhost]# perf report -i perf.data |grep vmf > >>> >>> Signed-off-by: Kefeng Wang >>> --- >>> mm/memory.c | 9 +++++---- >>> 1 file changed, 5 insertions(+), 4 deletions(-) >>> >>> diff --git a/mm/memory.c b/mm/memory.c >>> index 5ae2409d3cb9..a6afc96001e6 100644 >>> --- a/mm/memory.c >>> +++ b/mm/memory.c >>> @@ -117,6 +117,9 @@ static bool vmf_orig_pte_uffd_wp(struct vm_fault *vmf) >> >> >> if (!IS_ENABLED(CONFIG_PTE_MARKER_UFFD_WP)) >> return false; >> >> Will add config check too, > > pte_marker_uffd_wp() returns false when !PTE_MARKER_UFFD_WP, so kind of > imply this. I assume you meant to avoid checking ORIG_PTE_VALID flag, but Just to avoid checking ORIG_PTE_VALID and the new userfaultfd_wp() since it is not supported on most archs. > the flags is pretty hot too. Again, just want to double check with you on > whether it can have such a huge difference, e.g., how that compares with > the current code v.s. original patch v.s. this squashed. I will change the changelog to show different about vmf_orig_pte_uffd_wp from perf data. Thanks.