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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 84499C4361A for ; Fri, 4 Dec 2020 16:26:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5830322A85 for ; Fri, 4 Dec 2020 16:26:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728950AbgLDQ0O (ORCPT ); Fri, 4 Dec 2020 11:26:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55492 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727639AbgLDQ0N (ORCPT ); Fri, 4 Dec 2020 11:26:13 -0500 Received: from mail-ej1-x643.google.com (mail-ej1-x643.google.com [IPv6:2a00:1450:4864:20::643]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 884DDC0613D1 for ; Fri, 4 Dec 2020 08:25:33 -0800 (PST) Received: by mail-ej1-x643.google.com with SMTP id lt17so9536454ejb.3 for ; Fri, 04 Dec 2020 08:25:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RcTmsxVbOJXkWM5Hd5SB+R3sckednkoKgaMSdIRGnRE=; b=BcNTUMTtlQkxrPmb8zwbLGhYkGaL1vhWr2vSKVnV5wLvzJwwaI1BabmFIU88VcHUXP M6t4GH6Nr1FMOhQIMKR2x8CTrozIO4CbJ1z2EX3szggx4QAxb4NYfdm6woogfEitJ8kb M8vxO/HdApAQk7WajLexNjGmNkTeNiYGh1dee2+5Cjs5GA4Ecdtb1Ul06fa63h/MyE1g nq+zwU8QfUFUpTOYUw900hLOx6aURLnXhuceee2TZHEk3rXFEquI5n7WL7qo58pdvIFd NOADsGKMx0moo034Two+05D1x2sEL0SdZgQhlVJ/Jl6FR3qBUZQnmk25q/ub5YICUhfv jJBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RcTmsxVbOJXkWM5Hd5SB+R3sckednkoKgaMSdIRGnRE=; b=oM0TITRLcb0B+eTz3m+OqytqFBxxRUZK1d30Eu36tvWICILj5Ojtc2IAKuwsMKAJVk UJLdudQlrJLClW2OBAFkcFa/ozNaxPYr5mGNjF6RcVtTH8CPo29y1Hy2jbgZK8LGQh6F PxIFrE7N7LeT8GrbfXnQSTomVww5afeY8jS8VJLvC5EPCyOsaCTndE/pvvWhC5060R7M QDBjMhKb2iEaXmCnzZLH3P9kps/vsD4xYWVIPeCcDf4Ng24ayK0fiWfCIYNAOZGzWMP2 SDcokF36myY6qA5hxu1shRnZn0WkZNP6omKwh8rds9W8iWSWlamE3RzxoFYavzboU9uz GD3g== X-Gm-Message-State: AOAM530K5C/PRG0rI4Uc87h9n1c429dXkzPePevZHIQoZ3xwqWg51KHO 5CZ1d+OW7RUe2Ecj1A9BD4S5so6wNsgcffhYuRcL+Q== X-Google-Smtp-Source: ABdhPJyivwFLyiwC19rebyhYcjkL7E31HaDvHjPDfUxYj8m6f5YO1jMlPyOLhiC8FL25D7PTrVIZ5D53xiUskv/I7yA= X-Received: by 2002:a17:906:fb9b:: with SMTP id lr27mr8076906ejb.175.1607099132312; Fri, 04 Dec 2020 08:25:32 -0800 (PST) MIME-Version: 1.0 References: <20201202052330.474592-7-pasha.tatashin@soleen.com> <20201202163507.GL5487@ziepe.ca> <20201203010809.GQ5487@ziepe.ca> <20201203141729.GS5487@ziepe.ca> <20201203165937.GU5487@ziepe.ca> <20201203193607.GV5487@ziepe.ca> In-Reply-To: <20201203193607.GV5487@ziepe.ca> From: Pavel Tatashin Date: Fri, 4 Dec 2020 11:24:56 -0500 Message-ID: Subject: Re: [PATCH 6/6] mm/gup: migrate pinned pages out of movable zone To: Jason Gunthorpe Cc: LKML , linux-mm , Andrew Morton , Vlastimil Babka , Michal Hocko , David Hildenbrand , Oscar Salvador , Dan Williams , Sasha Levin , Tyler Hicks , Joonsoo Kim , mike.kravetz@oracle.com, Steven Rostedt , Ingo Molnar , Peter Zijlstra , Mel Gorman , Matthew Wilcox , David Rientjes , John Hubbard Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 3, 2020 at 2:36 PM Jason Gunthorpe wrote: > > On Thu, Dec 03, 2020 at 02:15:36PM -0500, Pavel Tatashin wrote: > > > I studied some more, and I think this is not a race: > > list_add_tail(&head->lru, &cma_page_list) is called only when > > isolate_lru_page(head) succeeds. > > isolate_lru_page(head) succeeds only when PageLRU(head) is true. > > However, in this function we also clear LRU flag before returning > > success. > > This means, that if we race with another thread, the other thread > > won't get to unprotected list_add_tail(&head->lru, &cma_page_list) > > until head is is back on LRU list. > > Oh interesting, I totally didn't see how that LRU stuff is > working. So.. this creates a ridiculously expensive spin lock? Not > broken, but yikes :| Not really a spin lock, the second thread won't be able to isolate this page, and will skip migration of this page. > > Jason 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 X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FE85C4361A for ; Fri, 4 Dec 2020 16:25:36 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C4271229C5 for ; Fri, 4 Dec 2020 16:25:35 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C4271229C5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=soleen.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id EA7AB6B0073; Fri, 4 Dec 2020 11:25:34 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E59206B0078; Fri, 4 Dec 2020 11:25:34 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D6F536B007B; Fri, 4 Dec 2020 11:25:34 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id BEDAF6B0073 for ; Fri, 4 Dec 2020 11:25:34 -0500 (EST) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 6D01D3625 for ; Fri, 4 Dec 2020 16:25:34 +0000 (UTC) X-FDA: 77556125388.21.hen57_580f379273c5 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin21.hostedemail.com (Postfix) with ESMTP id 355E4180442C3 for ; Fri, 4 Dec 2020 16:25:34 +0000 (UTC) X-HE-Tag: hen57_580f379273c5 X-Filterd-Recvd-Size: 4660 Received: from mail-ej1-f67.google.com (mail-ej1-f67.google.com [209.85.218.67]) by imf41.hostedemail.com (Postfix) with ESMTP for ; Fri, 4 Dec 2020 16:25:33 +0000 (UTC) Received: by mail-ej1-f67.google.com with SMTP id lt17so9536453ejb.3 for ; Fri, 04 Dec 2020 08:25:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=RcTmsxVbOJXkWM5Hd5SB+R3sckednkoKgaMSdIRGnRE=; b=BcNTUMTtlQkxrPmb8zwbLGhYkGaL1vhWr2vSKVnV5wLvzJwwaI1BabmFIU88VcHUXP M6t4GH6Nr1FMOhQIMKR2x8CTrozIO4CbJ1z2EX3szggx4QAxb4NYfdm6woogfEitJ8kb M8vxO/HdApAQk7WajLexNjGmNkTeNiYGh1dee2+5Cjs5GA4Ecdtb1Ul06fa63h/MyE1g nq+zwU8QfUFUpTOYUw900hLOx6aURLnXhuceee2TZHEk3rXFEquI5n7WL7qo58pdvIFd NOADsGKMx0moo034Two+05D1x2sEL0SdZgQhlVJ/Jl6FR3qBUZQnmk25q/ub5YICUhfv jJBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=RcTmsxVbOJXkWM5Hd5SB+R3sckednkoKgaMSdIRGnRE=; b=DzEm4yy56ODrsxRfuYN8ERcndYeVOQ5ISsYsQIaydBQVPTcDoxHTJq2Z/RJSoIqYJ5 Sun0Qooya0S7l7Nvvj7xHtDtk5XrDWCRfPsJ5FLG9pCV0791XgzkRdD2CJMvLghoSQra NbrCL5cu17CxJ0ohwWuiAB//q3AvsDTR1RJyvkE5pEvvP6uxEdm2GfzQCDCcyXw+pwkQ uO3F4gh7Ig70faqL16oB0+xv6HgXpZNgAYER2692++vAZvmR9UG9o/FHz5esRFT9osYw 6wxarzMQAw4cVwVZfNcNRypiwvN8PtxoykXUVUDgmpkOF7QT9xpOqE/DKyn5RfRC5y33 bTBA== X-Gm-Message-State: AOAM531ON/9TjTFeoIbhTO/wPUJtkqhlWt8laVxZ86gwW/qesry5LCm/ om2RCw1+M/j5OFiqLVv0KdyGhGD1/BuCkPn+q86lFA== X-Google-Smtp-Source: ABdhPJyivwFLyiwC19rebyhYcjkL7E31HaDvHjPDfUxYj8m6f5YO1jMlPyOLhiC8FL25D7PTrVIZ5D53xiUskv/I7yA= X-Received: by 2002:a17:906:fb9b:: with SMTP id lr27mr8076906ejb.175.1607099132312; Fri, 04 Dec 2020 08:25:32 -0800 (PST) MIME-Version: 1.0 References: <20201202052330.474592-7-pasha.tatashin@soleen.com> <20201202163507.GL5487@ziepe.ca> <20201203010809.GQ5487@ziepe.ca> <20201203141729.GS5487@ziepe.ca> <20201203165937.GU5487@ziepe.ca> <20201203193607.GV5487@ziepe.ca> In-Reply-To: <20201203193607.GV5487@ziepe.ca> From: Pavel Tatashin Date: Fri, 4 Dec 2020 11:24:56 -0500 Message-ID: Subject: Re: [PATCH 6/6] mm/gup: migrate pinned pages out of movable zone To: Jason Gunthorpe Cc: LKML , linux-mm , Andrew Morton , Vlastimil Babka , Michal Hocko , David Hildenbrand , Oscar Salvador , Dan Williams , Sasha Levin , Tyler Hicks , Joonsoo Kim , mike.kravetz@oracle.com, Steven Rostedt , Ingo Molnar , Peter Zijlstra , Mel Gorman , Matthew Wilcox , David Rientjes , John Hubbard Content-Type: text/plain; charset="UTF-8" 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: On Thu, Dec 3, 2020 at 2:36 PM Jason Gunthorpe wrote: > > On Thu, Dec 03, 2020 at 02:15:36PM -0500, Pavel Tatashin wrote: > > > I studied some more, and I think this is not a race: > > list_add_tail(&head->lru, &cma_page_list) is called only when > > isolate_lru_page(head) succeeds. > > isolate_lru_page(head) succeeds only when PageLRU(head) is true. > > However, in this function we also clear LRU flag before returning > > success. > > This means, that if we race with another thread, the other thread > > won't get to unprotected list_add_tail(&head->lru, &cma_page_list) > > until head is is back on LRU list. > > Oh interesting, I totally didn't see how that LRU stuff is > working. So.. this creates a ridiculously expensive spin lock? Not > broken, but yikes :| Not really a spin lock, the second thread won't be able to isolate this page, and will skip migration of this page. > > Jason