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=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 1E774C4360C for ; Fri, 27 Sep 2019 21:44:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CBD972146E for ; Fri, 27 Sep 2019 21:44:50 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="Q7xnwh8V" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728304AbfI0Vou (ORCPT ); Fri, 27 Sep 2019 17:44:50 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:42374 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726029AbfI0Vou (ORCPT ); Fri, 27 Sep 2019 17:44:50 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x8RLdUcN001264; Fri, 27 Sep 2019 21:44:37 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2019-08-05; bh=Hk4zBrC4ftfxAK0GhvkCyWFjYJFlQ+AvZq80XV4tPQs=; b=Q7xnwh8VBKvYk0s/2s9ZAa4695mEN9M9MFwzaIRE3OKTzVqDb/gKe5JsdrJEjYCyYcOB 9glF6Fck3L5gO7KleN7dlcWAKToYfpDiY10+ks7JdU3VVd6LVyBQ44JfpqHus0l5UEis rbzmMH/8oXwt9HXCMgMmLoFsT+9fgfao1zIzjimBRvxSp7F+VeZm4+ZNhK2CAsJENQ1+ qQsMd7+ISG+IlEywedVmRTIQLuLQMbRucqvrkeDawVtfFe6m3qyBU0Op1ybCRsxPXDUw ikoDYUFB4IQBM9+7w6xZKKBuPvmeCzR+BU964W41P/frBjsuXq+njNF490CeAI5smCry Pg== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by userp2120.oracle.com with ESMTP id 2v5cgrmm6f-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 27 Sep 2019 21:44:37 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x8RLiEWt129975; Fri, 27 Sep 2019 21:44:36 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3020.oracle.com with ESMTP id 2v9m3fq4v7-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 27 Sep 2019 21:44:36 +0000 Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x8RLiZX0004387; Fri, 27 Sep 2019 21:44:35 GMT Received: from [192.168.1.222] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 27 Sep 2019 14:44:35 -0700 Subject: Re: [PATCH v5 4/7] hugetlb: disable region_add file_region coalescing To: Mina Almasry Cc: shuah@kernel.org, rientjes@google.com, shakeelb@google.com, gthelen@google.com, akpm@linux-foundation.org, khalid.aziz@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com, mkoutny@suse.com References: <20190919222421.27408-1-almasrymina@google.com> <20190919222421.27408-5-almasrymina@google.com> From: Mike Kravetz Message-ID: <62a2a742-1735-7272-3c6c-213efc7adb9f@oracle.com> Date: Fri, 27 Sep 2019 14:44:33 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190919222421.27408-5-almasrymina@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9393 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909270183 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9393 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1908290000 definitions=main-1909270183 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 9/19/19 3:24 PM, Mina Almasry wrote: > A follow up patch in this series adds hugetlb cgroup uncharge info the > file_region entries in resv->regions. The cgroup uncharge info may > differ for different regions, so they can no longer be coalesced at > region_add time. So, disable region coalescing in region_add in this > patch. > > Behavior change: > > Say a resv_map exists like this [0->1], [2->3], and [5->6]. > > Then a region_chg/add call comes in region_chg/add(f=0, t=5). > > Old code would generate resv->regions: [0->5], [5->6]. > New code would generate resv->regions: [0->1], [1->2], [2->3], [3->5], > [5->6]. > > Special care needs to be taken to handle the resv->adds_in_progress > variable correctly. In the past, only 1 region would be added for every > region_chg and region_add call. But now, each call may add multiple > regions, so we can no longer increment adds_in_progress by 1 in region_chg, > or decrement adds_in_progress by 1 after region_add or region_abort. Instead, > region_chg calls add_reservation_in_range() to count the number of regions > needed and allocates those, and that info is passed to region_add and > region_abort to decrement adds_in_progress correctly. > > Signed-off-by: Mina Almasry > > --- > mm/hugetlb.c | 273 +++++++++++++++++++++++++++++---------------------- > 1 file changed, 158 insertions(+), 115 deletions(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index bac1cbdd027c..d03b048084a3 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -244,6 +244,12 @@ struct file_region { > long to; > }; > > +/* Helper that removes a struct file_region from the resv_map cache and returns > + * it for use. > + */ > +static struct file_region * > +get_file_region_entry_from_cache(struct resv_map *resv, long from, long to); > + Instead of the forward declaration, just put the function here. > /* Must be called with resv->lock held. Calling this with count_only == true > * will count the number of pages to be added but will not modify the linked > * list. > @@ -251,51 +257,61 @@ struct file_region { > static long add_reservation_in_range(struct resv_map *resv, long f, long t, > bool count_only) > { > - long chg = 0; > + long add = 0; > struct list_head *head = &resv->regions; > + long last_accounted_offset = f; > struct file_region *rg = NULL, *trg = NULL, *nrg = NULL; > > - /* Locate the region we are before or in. */ > - list_for_each_entry (rg, head, link) > - if (f <= rg->to) > - break; > - > - /* Round our left edge to the current segment if it encloses us. */ > - if (f > rg->from) > - f = rg->from; > - > - chg = t - f; > + /* In this loop, we essentially handle an entry for the range > + * last_accounted_offset -> rg->from, at every iteration, with some > + * bounds checking. > + */ > + list_for_each_entry_safe(rg, trg, head, link) { > + /* Skip irrelevant regions that start before our range. */ > + if (rg->from < f) { > + /* If this region ends after the last accounted offset, > + * then we need to update last_accounted_offset. > + */ > + if (rg->to > last_accounted_offset) > + last_accounted_offset = rg->to; > + continue; > + } > > - /* Check for and consume any regions we now overlap with. */ > - nrg = rg; > - list_for_each_entry_safe (rg, trg, rg->link.prev, link) { > - if (&rg->link == head) > - break; > + /* When we find a region that starts beyond our range, we've > + * finished. > + */ > if (rg->from > t) > break; > > - /* We overlap with this area, if it extends further than > - * us then we must extend ourselves. Account for its > - * existing reservation. > + /* Add an entry for last_accounted_offset -> rg->from, and > + * update last_accounted_offset. > */ > - if (rg->to > t) { > - chg += rg->to - t; > - t = rg->to; > + if (rg->from > last_accounted_offset) { > + add += rg->from - last_accounted_offset; > + if (!count_only) { > + nrg = get_file_region_entry_from_cache( > + resv, last_accounted_offset, rg->from); > + list_add(&nrg->link, rg->link.prev); > + } > } > - chg -= rg->to - rg->from; > > - if (!count_only && rg != nrg) { > - list_del(&rg->link); > - kfree(rg); > - } > + last_accounted_offset = rg->to; > } > > - if (!count_only) { > - nrg->from = f; > - nrg->to = t; > + /* Handle the case where our range extends beyond > + * last_accounted_offset. > + */ > + if (last_accounted_offset < t) { > + add += t - last_accounted_offset; > + if (!count_only) { > + nrg = get_file_region_entry_from_cache( > + resv, last_accounted_offset, t); > + list_add(&nrg->link, rg->link.prev); > + } > + last_accounted_offset = t; > } > > - return chg; > + return add; > } > > /* > @@ -305,46 +321,24 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t, The start of this comment block says, /* * Add the huge page range represented by [f, t) to the reserve * map. Existing regions will be expanded to accommodate the specified * range, or a region will be taken from the cache. We are no longer expanding existing regions. Correct? As an optimization, I guess we could coalesce/combine reion entries as long as they are for the same cgroup. However, it may not be worth the effort. > * must exist in the cache due to the previous call to region_chg with > * the same range. > * > + * regions_needed is the out value provided by a previous > + * call to region_chg. > + * > * Return the number of new huge pages added to the map. This > * number is greater than or equal to zero. > */ > -static long region_add(struct resv_map *resv, long f, long t) > +static long region_add(struct resv_map *resv, long f, long t, > + long regions_needed) > { > - struct list_head *head = &resv->regions; > - struct file_region *rg, *nrg; > long add = 0; > > spin_lock(&resv->lock); > - /* Locate the region we are either in or before. */ > - list_for_each_entry(rg, head, link) > - if (f <= rg->to) > - break; > > - /* > - * If no region exists which can be expanded to include the > - * specified range, pull a region descriptor from the cache > - * and use it for this range. > - */ > - if (&rg->link == head || t < rg->from) { > - VM_BUG_ON(resv->region_cache_count <= 0); > - > - resv->region_cache_count--; > - nrg = list_first_entry(&resv->region_cache, struct file_region, > - link); > - list_del(&nrg->link); > - > - nrg->from = f; > - nrg->to = t; > - list_add(&nrg->link, rg->link.prev); > - > - add += t - f; > - goto out_locked; > - } > + VM_BUG_ON(resv->region_cache_count < regions_needed); > > add = add_reservation_in_range(resv, f, t, false); > + resv->adds_in_progress -= regions_needed; Consider this example, - region_chg(1,2) adds_in_progress = 1 cache entries 1 - region_chg(3,4) adds_in_progress = 2 cache entries 2 - region_chg(5,6) adds_in_progress = 3 cache entries 3 At this point, no region descriptors are in the map because only region_chg has been called. - region_chg(0,6) adds_in_progress = 4 cache entries 4 Is that correct so far? Then the following sequence happens, - region_add(1,2) adds_in_progress = 3 cache entries 3 - region_add(3,4) adds_in_progress = 2 cache entries 2 - region_add(5,6) adds_in_progress = 1 cache entries 1 list of region descriptors is: [1->2] [3->4] [5->6] - region_add(0,6) This is going to require 3 cache entries but only one is in the cache. I think we are going to BUG in get_file_region_entry_from_cache() the second time it is called from add_reservation_in_range(). I stopped looking at the code here as things will need to change if this is a real issue. -- Mike Kravetz