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Thu, 06 Feb 2020 22:31:49 +0000 Received: from abhmp0001.oracle.com (abhmp0001.oracle.com [141.146.116.7]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 016MVmgm024222; Thu, 6 Feb 2020 22:31:48 GMT Received: from [192.168.1.206] (/71.63.128.209) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 06 Feb 2020 14:31:48 -0800 Subject: Re: [PATCH v11 6/9] hugetlb_cgroup: support noreserve mappings To: Mina Almasry Cc: shuah@kernel.org, rientjes@google.com, shakeelb@google.com, gthelen@google.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, cgroups@vger.kernel.org References: <20200203232248.104733-1-almasrymina@google.com> <20200203232248.104733-6-almasrymina@google.com> From: Mike Kravetz Message-ID: <6cc406e7-757f-4922-ffc0-681df3ee0d18@oracle.com> Date: Thu, 6 Feb 2020 14:31:46 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <20200203232248.104733-6-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=9523 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1911140001 definitions=main-2002060162 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9523 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=2 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=8.0.1-1911140001 definitions=main-2002060162 Sender: linux-kselftest-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 2/3/20 3:22 PM, Mina Almasry wrote: > Support MAP_NORESERVE accounting as part of the new counter. > > For each hugepage allocation, at allocation time we check if there is > a reservation for this allocation or not. If there is a reservation for > this allocation, then this allocation was charged at reservation time, > and we don't re-account it. If there is no reserevation for this > allocation, we charge the appropriate hugetlb_cgroup. > > The hugetlb_cgroup to uncharge for this allocation is stored in > page[3].private. We use new APIs added in an earlier patch to set this > pointer. Ah! That reminded me to look at the migration code. Turns out that none of the existing cgroup information (page[2]) is being migrated today. That is a bug. :( I'll confirm and fix in a patch separate from this series. We will need to make sure that new information added by this series in page[3] is also migrated. That would be in an earlier patch where the use of the field is introduced. > > Signed-off-by: Mina Almasry > > --- > > Changes in v10: > - Refactored deferred_reserve check. > > --- > mm/hugetlb.c | 28 +++++++++++++++++++++++++++- > 1 file changed, 27 insertions(+), 1 deletion(-) > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 33818ccaf7e89..ec0b55ea1506e 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1339,6 +1339,9 @@ static void __free_huge_page(struct page *page) > clear_page_huge_active(page); > hugetlb_cgroup_uncharge_page(hstate_index(h), pages_per_huge_page(h), > page, false); > + hugetlb_cgroup_uncharge_page(hstate_index(h), pages_per_huge_page(h), > + page, true); > + When looking at the code without change markings, the two above lines look so similar my first thought is there must be a mistake. A suggestion for better code readability: - hugetlb_cgroup_uncharge_page could just take "struct hstate *h" and get both hstate_index(h) and pages_per_huge_page(h). - Perhaps make hugetlb_cgroup_uncharge_page and hugetlb_cgroup_uncharge_page_rsvd be wrappers around a common routine. Then the above would look like: hugetlb_cgroup_uncharge_page(h, page); hugetlb_cgroup_uncharge_page_rsvd(h, page); > if (restore_reserve) > h->resv_huge_pages++; > > @@ -2172,6 +2175,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, > long gbl_chg; > int ret, idx; > struct hugetlb_cgroup *h_cg; > + bool deferred_reserve; > > idx = hstate_index(h); > /* > @@ -2209,10 +2213,20 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, > gbl_chg = 1; > } > > + /* If this allocation is not consuming a reservation, charge it now. > + */ > + deferred_reserve = map_chg || avoid_reserve || !vma_resv_map(vma); > + if (deferred_reserve) { > + ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), > + &h_cg, true); > + if (ret) > + goto out_subpool_put; > + } > + > ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg, > false); Hmmm? I'm starting to like the wrapper idea more as a way to help with readability of the bool rsvd argument. hugetlb_cgroup_charge_cgroup_rsvd() hugetlb_cgroup_charge_cgroup() At least to me it makes it easier to read. -- Mike Kravetz > if (ret) > - goto out_subpool_put; > + goto out_uncharge_cgroup_reservation; > > spin_lock(&hugetlb_lock); > /* > @@ -2236,6 +2250,14 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, > } > hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, page, > false); > + /* If allocation is not consuming a reservation, also store the > + * hugetlb_cgroup pointer on the page. > + */ > + if (deferred_reserve) { > + hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, > + page, true); > + } > + > spin_unlock(&hugetlb_lock); > > set_page_private(page, (unsigned long)spool); > @@ -2261,6 +2283,10 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, > out_uncharge_cgroup: > hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg, > false); > +out_uncharge_cgroup_reservation: > + if (deferred_reserve) > + hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), > + h_cg, true); > out_subpool_put: > if (map_chg || avoid_reserve) > hugepage_subpool_put_pages(spool, 1); > -- > 2.25.0.341.g760bfbb309-goog