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Mon, 24 Feb 2020 14:27:04 -0800 (PST) Received: from [100.112.92.218] ([104.133.9.106]) by smtp.gmail.com with ESMTPSA id v25sm13820038pfe.147.2020.02.24.14.27.02 (version=TLS1 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Mon, 24 Feb 2020 14:27:03 -0800 (PST) Date: Mon, 24 Feb 2020 14:26:45 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Dan Schatzberg cc: Jens Axboe , Tejun Heo , Li Zefan , Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Hugh Dickins , Roman Gushchin , Shakeel Butt , Chris Down , Yang Shi , Thomas Gleixner , "open list:BLOCK LAYER" , open list , "open list:CONTROL GROUP (CGROUP)" , "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" Subject: Re: [PATCH v3 2/3] mm: Charge active memcg when no mm is set In-Reply-To: <4456276af198412b2d41cd09d246cd20e0c6d22a.1582581887.git.schatzberg.dan@gmail.com> Message-ID: References: <4456276af198412b2d41cd09d246cd20e0c6d22a.1582581887.git.schatzberg.dan@gmail.com> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII 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 Mon, 24 Feb 2020, Dan Schatzberg wrote: > memalloc_use_memcg() worked for kernel allocations but was silently > ignored for user pages. > > This patch establishes a precedence order for who gets charged: > > 1. If there is a memcg associated with the page already, that memcg is > charged. This happens during swapin. > > 2. If an explicit mm is passed, mm->memcg is charged. This happens > during page faults, which can be triggered in remote VMs (eg gup). > > 3. Otherwise consult the current process context. If it has configured > a current->active_memcg, use that. Otherwise, current->mm->memcg. > > Previously, if a NULL mm was passed to mem_cgroup_try_charge (case 3) it > would always charge the root cgroup. Now it looks up the current > active_memcg first (falling back to charging the root cgroup if not > set). > > Signed-off-by: Dan Schatzberg > Acked-by: Johannes Weiner > Acked-by: Tejun Heo > Acked-by: Chris Down Acked-by: Hugh Dickins > Reviewed-by: Shakeel Butt > Signed-off-by: Dan Schatzberg > --- > mm/memcontrol.c | 11 ++++++++--- > mm/shmem.c | 4 ++-- > 2 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index d09776cd6e10..222e4aac0c85 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6319,7 +6319,8 @@ enum mem_cgroup_protection mem_cgroup_protected(struct mem_cgroup *root, > * @compound: charge the page as compound or small page > * > * Try to charge @page to the memcg that @mm belongs to, reclaiming > - * pages according to @gfp_mask if necessary. > + * pages according to @gfp_mask if necessary. If @mm is NULL, try to > + * charge to the active memcg. > * > * Returns 0 on success, with *@memcgp pointing to the charged memcg. > * Otherwise, an error code is returned. > @@ -6363,8 +6364,12 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm, > } > } > > - if (!memcg) > - memcg = get_mem_cgroup_from_mm(mm); > + if (!memcg) { > + if (!mm) > + memcg = get_mem_cgroup_from_current(); > + else > + memcg = get_mem_cgroup_from_mm(mm); > + } > > ret = try_charge(memcg, gfp_mask, nr_pages); > > diff --git a/mm/shmem.c b/mm/shmem.c > index c8f7540ef048..8664c97851f2 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -1631,7 +1631,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, > { > struct address_space *mapping = inode->i_mapping; > struct shmem_inode_info *info = SHMEM_I(inode); > - struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm; > + struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL; > struct mem_cgroup *memcg; > struct page *page; > swp_entry_t swap; > @@ -1766,7 +1766,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, > } > > sbinfo = SHMEM_SB(inode->i_sb); > - charge_mm = vma ? vma->vm_mm : current->mm; > + charge_mm = vma ? vma->vm_mm : NULL; > > page = find_lock_entry(mapping, index); > if (xa_is_value(page)) { > -- > 2.17.1