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[46.53.177.92]) by smtp.gmail.com with ESMTPSA id e20-v6sm4883031eds.20.2018.07.24.11.29.09 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Jul 2018 11:29:10 -0700 (PDT) Date: Tue, 24 Jul 2018 21:29:08 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, dancol@google.com, vbabka@suse.cz Subject: Re: + mm-proc-pid-smaps_rollup-convert-to-single-value-seq_file.patch added to -mm tree Message-ID: <20180724182908.GD27053@avx2> References: <20180723235548.nLTzP%akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180723235548.nLTzP%akpm@linux-foundation.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 23, 2018 at 04:55:48PM -0700, akpm@linux-foundation.org wrote: > The patch titled > Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file > has been added to the -mm tree. Its filename is > mm-proc-pid-smaps_rollup-convert-to-single-value-seq_file.patch > Subject: mm: /proc/pid/smaps_rollup: convert to single value seq_file > > The /proc/pid/smaps_rollup file is currently implemented via the > m_start/m_next/m_stop seq_file iterators shared with the other maps files, > that iterate over vma's. However, the rollup file doesn't print anything > for each vma, only accumulate the stats. What I don't understand why keep seq_ops then and not do all the work in ->show hook. Currently /proc/*/smaps_rollup is at ~500 bytes so with minimum 1 page seq buffer, no buffer resizing is possible. > +static int show_smaps_rollup(struct seq_file *m, void *v) > +{ > + struct proc_maps_private *priv = m->private; > + struct mem_size_stats *mss = priv->rollup; > + struct vm_area_struct *vma; > + > + /* > + * We might be called multiple times when e.g. the seq buffer > + * overflows. Gather the stats only once. It doesn't! > + if (!mss->finished) { > + for (vma = priv->mm->mmap; vma; vma = vma->vm_next) { > + smap_gather_stats(vma, mss); > + mss->last_vma_end = vma->vm_end; > } > - last_vma = !m_next_vma(priv, vma); > - } else { > - rollup_mode = false; > - memset(&mss_stack, 0, sizeof(mss_stack)); > - mss = &mss_stack;