From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F315CCD4F5B for ; Tue, 19 May 2026 12:46:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=0tEY/ViETcYWqMbew+LgZ2oRYOW85rqGc3tYxA7i0ak=; b=o4dvb3wk5u59uy7FuLiRQjElLM ZIQrXP5v7kZsVfpIDjmxywq9QRegW694UPYhX1rNJFFVd5qp5J0ZmhljSXi9XjHEdyq7XhJG8jN6Y 2qbepqAbl/z8U1sbQAYc1vYN99MFDeDGMHgGNnHCZ5HaboYSJGwn60fjBiZr+4O7hNAIm81RlCgEU ezuOSaFsxsUrChWaZom4lp/AwNRjvXL7EhRQTH5sowJRlgez+HhXxX2cy41/xLiyGYXzf56qcUyNZ wQNZrady9QzzL5BVn6MKPnmSTZiQ498T2dFZUv4vQJrD1gtHmFdYp0yJ1e9lPwEVM4P2IdapLl7ES Kpv3jgaQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wPJpg-00000001Wb5-2kMF; Tue, 19 May 2026 12:46:00 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wPJpd-00000001WaS-3KSP; Tue, 19 May 2026 12:45:58 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 070F240267; Tue, 19 May 2026 12:45:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B010C2BCB8; Tue, 19 May 2026 12:45:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779194756; bh=0tEY/ViETcYWqMbew+LgZ2oRYOW85rqGc3tYxA7i0ak=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FfLpklXMkKT1W9LjHbc6orFesNSR/WYbThmN3RY3KQ+Sj526oZ9knAqWz1hOSb2V8 dNS1B12b6zt9T5UOXQ1nrMbNWtECIR2msv6pUBdn/ZjxEPvXzm8/CRvLKqnqCU51sq haxA77qodnAWypw1XScQZfjJLKwh9FciR3mqwcEzxbVxwnrLWlqLfHqEPk5J3o8Cmy 0Wlh1tz1PaNb1cIMkhcRqDoftNLeYh74seeYdw4fbd1+VoscIEyfDFSquLrWTQHUK9 L8E52Y782Q8/1j6v9de5qhI08YuU7rlNh8jgJpwnmYyrNumFGmR+cEYpT6UhTkfXca +brOZETnCxkNA== Date: Tue, 19 May 2026 13:45:46 +0100 From: Lorenzo Stoakes To: Barry Song Cc: Suren Baghdasaryan , Matthew Wilcox , akpm@linux-foundation.org, linux-mm@kvack.org, david@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, mhocko@suse.com, jack@suse.cz, pfalcato@suse.de, wanglian@kylinos.cn, chentao@kylinos.cn, lianux.mm@gmail.com, kunwu.chan@gmail.com, liyangouwen1@oppo.com, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, Nanzhe Zhao Subject: Re: [PATCH v2 0/5] mm: reduce mmap_lock contention and improve page fault performance Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260519_054557_871614_0E5716BC X-CRM114-Status: GOOD ( 25.67 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, May 19, 2026 at 05:14:45AM +0800, Barry Song wrote: > On Tue, May 19, 2026 at 3:57 AM Suren Baghdasaryan wrote: > > > > On Mon, May 18, 2026 at 4:26 AM Barry Song wrote: > > > > > > On Mon, May 18, 2026 at 5:47 PM Lorenzo Stoakes wrote: > > > > > > > > On Sun, May 17, 2026 at 04:45:15PM +0800, Barry Song wrote: > [...] > > > > > > I think we either need to fix `fork()`, or keep the current > > > behavior of dropping the VMA lock before performing I/O. > > > > I see. So, this problem arises from the fact that we are changing the > > pagefaults requiring I/O operation to hold VMA lock... > > And you want to lock VMA on fork only if vma_is_anonymous(vma) || > > is_cow_mapping(vma->vm_flags). So, we will be blocking page faults for > > anonymous and COW VMAs only while holding mmap_write_lock, preventing > > any VMA modification. On the surface, that looks ok to me but I might > > be missing some corner cases. If nobody sees any obvious issues, I > > think it's worth a try. > > > > Thanks. Besides the creation of processes via fork(), I > am also beginning to worry about the death of processes. > > One thing that came to my mind this morning > is that when lowmemorykiller decides to kill an app, we What's the lowmemorykiller? :P you mean the OOM killer? > want the memory to be released as quickly as possible so > the new app or user scenario can get memory sooner. > > In that case, if the app being killed is performing I/O > while holding the VMA lock, the unmapping procedure > could end up being blocked as well. > > If we release the VMA lock as we currently do, we allow > process exit to proceed. > > I haven't thought it through very clearly yet, and I > may be wrong. I'd like to do more investigation. I hope > the apps being killed stay very still, but who knows—we > have so many applications in the market. Yeah let's tread very carefully please, you're picking two of the most fraught areas of mm, I'm not going to want to see changes there unless they're substantially more convincingly argued. > > Meanwhile, if you have any comments regarding the death > of processes, they would be very welcome. As above, leave it alone please :) > > Best Regards > Barry Thanks, Lorenzo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 636F4CD4F5B for ; Tue, 19 May 2026 12:46:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=1boaujot4LYl35eaAPLeWbM3jINJ2XZK34RJmsA1d2k=; 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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779194756; bh=0tEY/ViETcYWqMbew+LgZ2oRYOW85rqGc3tYxA7i0ak=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FfLpklXMkKT1W9LjHbc6orFesNSR/WYbThmN3RY3KQ+Sj526oZ9knAqWz1hOSb2V8 dNS1B12b6zt9T5UOXQ1nrMbNWtECIR2msv6pUBdn/ZjxEPvXzm8/CRvLKqnqCU51sq haxA77qodnAWypw1XScQZfjJLKwh9FciR3mqwcEzxbVxwnrLWlqLfHqEPk5J3o8Cmy 0Wlh1tz1PaNb1cIMkhcRqDoftNLeYh74seeYdw4fbd1+VoscIEyfDFSquLrWTQHUK9 L8E52Y782Q8/1j6v9de5qhI08YuU7rlNh8jgJpwnmYyrNumFGmR+cEYpT6UhTkfXca +brOZETnCxkNA== Date: Tue, 19 May 2026 13:45:46 +0100 From: Lorenzo Stoakes To: Barry Song Cc: Suren Baghdasaryan , Matthew Wilcox , akpm@linux-foundation.org, linux-mm@kvack.org, david@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, mhocko@suse.com, jack@suse.cz, pfalcato@suse.de, wanglian@kylinos.cn, chentao@kylinos.cn, lianux.mm@gmail.com, kunwu.chan@gmail.com, liyangouwen1@oppo.com, chrisl@kernel.org, kasong@tencent.com, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, youngjun.park@lge.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, Nanzhe Zhao Subject: Re: [PATCH v2 0/5] mm: reduce mmap_lock contention and improve page fault performance Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260519_054557_871614_0E5716BC X-CRM114-Status: GOOD ( 25.67 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org T24gVHVlLCBNYXkgMTksIDIwMjYgYXQgMDU6MTQ6NDVBTSArMDgwMCwgQmFycnkgU29uZyB3cm90 ZToKPiBPbiBUdWUsIE1heSAxOSwgMjAyNiBhdCAzOjU34oCvQU0gU3VyZW4gQmFnaGRhc2FyeWFu IDxzdXJlbmJAZ29vZ2xlLmNvbT4gd3JvdGU6Cj4gPgo+ID4gT24gTW9uLCBNYXkgMTgsIDIwMjYg YXQgNDoyNuKAr0FNIEJhcnJ5IFNvbmcgPGJhb2h1YUBrZXJuZWwub3JnPiB3cm90ZToKPiA+ID4K PiA+ID4gT24gTW9uLCBNYXkgMTgsIDIwMjYgYXQgNTo0N+KAr1BNIExvcmVuem8gU3RvYWtlcyA8 bGpzQGtlcm5lbC5vcmc+IHdyb3RlOgo+ID4gPiA+Cj4gPiA+ID4gT24gU3VuLCBNYXkgMTcsIDIw MjYgYXQgMDQ6NDU6MTVQTSArMDgwMCwgQmFycnkgU29uZyB3cm90ZToKPiBbLi4uXQo+ID4gPgo+ ID4gPiBJIHRoaW5rIHdlIGVpdGhlciBuZWVkIHRvIGZpeCBgZm9yaygpYCwgb3Iga2VlcCB0aGUg Y3VycmVudAo+ID4gPiBiZWhhdmlvciBvZiBkcm9wcGluZyB0aGUgVk1BIGxvY2sgYmVmb3JlIHBl cmZvcm1pbmcgSS9PLgo+ID4KPiA+IEkgc2VlLiBTbywgdGhpcyBwcm9ibGVtIGFyaXNlcyBmcm9t IHRoZSBmYWN0IHRoYXQgd2UgYXJlIGNoYW5naW5nIHRoZQo+ID4gcGFnZWZhdWx0cyByZXF1aXJp bmcgSS9PIG9wZXJhdGlvbiB0byBob2xkIFZNQSBsb2NrLi4uCj4gPiBBbmQgeW91IHdhbnQgdG8g bG9jayBWTUEgb24gZm9yayBvbmx5IGlmIHZtYV9pc19hbm9ueW1vdXModm1hKSB8fAo+ID4gaXNf Y293X21hcHBpbmcodm1hLT52bV9mbGFncykuIFNvLCB3ZSB3aWxsIGJlIGJsb2NraW5nIHBhZ2Ug ZmF1bHRzIGZvcgo+ID4gYW5vbnltb3VzIGFuZCBDT1cgVk1BcyBvbmx5IHdoaWxlIGhvbGRpbmcg bW1hcF93cml0ZV9sb2NrLCBwcmV2ZW50aW5nCj4gPiBhbnkgVk1BIG1vZGlmaWNhdGlvbi4gT24g dGhlIHN1cmZhY2UsIHRoYXQgbG9va3Mgb2sgdG8gbWUgYnV0IEkgbWlnaHQKPiA+IGJlIG1pc3Np bmcgc29tZSBjb3JuZXIgY2FzZXMuIElmIG5vYm9keSBzZWVzIGFueSBvYnZpb3VzIGlzc3Vlcywg SQo+ID4gdGhpbmsgaXQncyB3b3J0aCBhIHRyeS4KPiA+Cj4KPiBUaGFua3MuIEJlc2lkZXMgdGhl IGNyZWF0aW9uIG9mIHByb2Nlc3NlcyB2aWEgZm9yaygpLCBJCj4gYW0gYWxzbyBiZWdpbm5pbmcg dG8gd29ycnkgYWJvdXQgdGhlIGRlYXRoIG9mIHByb2Nlc3Nlcy4KPgo+IE9uZSB0aGluZyB0aGF0 IGNhbWUgdG8gbXkgbWluZCB0aGlzIG1vcm5pbmcKPiBpcyB0aGF0IHdoZW4gbG93bWVtb3J5a2ls bGVyIGRlY2lkZXMgdG8ga2lsbCBhbiBhcHAsIHdlCgpXaGF0J3MgdGhlIGxvd21lbW9yeWtpbGxl cj8gOlAgeW91IG1lYW4gdGhlIE9PTSBraWxsZXI/Cgo+IHdhbnQgdGhlIG1lbW9yeSB0byBiZSBy ZWxlYXNlZCBhcyBxdWlja2x5IGFzIHBvc3NpYmxlIHNvCj4gdGhlIG5ldyBhcHAgb3IgdXNlciBz Y2VuYXJpbyBjYW4gZ2V0IG1lbW9yeSBzb29uZXIuCj4KPiBJbiB0aGF0IGNhc2UsIGlmIHRoZSBh cHAgYmVpbmcga2lsbGVkIGlzIHBlcmZvcm1pbmcgSS9PCj4gd2hpbGUgaG9sZGluZyB0aGUgVk1B IGxvY2ssIHRoZSB1bm1hcHBpbmcgcHJvY2VkdXJlCj4gY291bGQgZW5kIHVwIGJlaW5nIGJsb2Nr ZWQgYXMgd2VsbC4KPgo+IElmIHdlIHJlbGVhc2UgdGhlIFZNQSBsb2NrIGFzIHdlIGN1cnJlbnRs eSBkbywgd2UgYWxsb3cKPiBwcm9jZXNzIGV4aXQgdG8gcHJvY2VlZC4KPgo+IEkgaGF2ZW4ndCB0 aG91Z2h0IGl0IHRocm91Z2ggdmVyeSBjbGVhcmx5IHlldCwgYW5kIEkKPiBtYXkgYmUgd3Jvbmcu IEknZCBsaWtlIHRvIGRvIG1vcmUgaW52ZXN0aWdhdGlvbi4gSSBob3BlCj4gdGhlIGFwcHMgYmVp bmcga2lsbGVkIHN0YXkgdmVyeSBzdGlsbCwgYnV0IHdobyBrbm93c+KAlHdlCj4gaGF2ZSBzbyBt YW55IGFwcGxpY2F0aW9ucyBpbiB0aGUgbWFya2V0LgoKWWVhaCBsZXQncyB0cmVhZCB2ZXJ5IGNh cmVmdWxseSBwbGVhc2UsIHlvdSdyZSBwaWNraW5nIHR3byBvZiB0aGUgbW9zdCBmcmF1Z2h0CmFy ZWFzIG9mIG1tLCBJJ20gbm90IGdvaW5nIHRvIHdhbnQgdG8gc2VlIGNoYW5nZXMgdGhlcmUgdW5s ZXNzIHRoZXkncmUKc3Vic3RhbnRpYWxseSBtb3JlIGNvbnZpbmNpbmdseSBhcmd1ZWQuCgo+Cj4g TWVhbndoaWxlLCBpZiB5b3UgaGF2ZSBhbnkgY29tbWVudHMgcmVnYXJkaW5nIHRoZSBkZWF0aAo+ IG9mIHByb2Nlc3NlcywgdGhleSB3b3VsZCBiZSB2ZXJ5IHdlbGNvbWUuCgpBcyBhYm92ZSwgbGVh dmUgaXQgYWxvbmUgcGxlYXNlIDopCgo+Cj4gQmVzdCBSZWdhcmRzCj4gQmFycnkKClRoYW5rcywg TG9yZW56bwoKX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18K bGludXgtcmlzY3YgbWFpbGluZyBsaXN0CmxpbnV4LXJpc2N2QGxpc3RzLmluZnJhZGVhZC5vcmcK aHR0cDovL2xpc3RzLmluZnJhZGVhZC5vcmcvbWFpbG1hbi9saXN0aW5mby9saW51eC1yaXNjdgo=