netdev - Re: [PATCH v5 bpf-next 1/4] bpf: introduce task_vma bpf

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Message-ID: <5286e70d-404d-f968-9694-f090eb8fd064@fb.com>
Date:   Mon, 8 Feb 2021 15:12:12 -0800
From:   Yonghong Song <yhs@...com>
To:     Song Liu <songliubraving@...com>, <bpf@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-mm@...ck.org>
CC:     <ast@...nel.org>, <daniel@...earbox.net>, <kernel-team@...com>,
        <akpm@...ux-foundation.org>
Subject: Re: [PATCH v5 bpf-next 1/4] bpf: introduce task_vma bpf_iter



On 2/8/21 2:52 PM, Song Liu wrote:
> Introduce task_vma bpf_iter to print memory information of a process. It
> can be used to print customized information similar to /proc/<pid>/maps.
> 
> Current /proc/<pid>/maps and /proc/<pid>/smaps provide information of
> vma's of a process. However, these information are not flexible enough to
> cover all use cases. For example, if a vma cover mixed 2MB pages and 4kB
> pages (x86_64), there is no easy way to tell which address ranges are
> backed by 2MB pages. task_vma solves the problem by enabling the user to
> generate customize information based on the vma (and vma->vm_mm,
> vma->vm_file, etc.).
> 
> To access the vma safely in the BPF program, task_vma iterator holds
> target mmap_lock while calling the BPF program. If the mmap_lock is
> contended, task_vma unlocks mmap_lock between iterations to unblock the
> writer(s). This lock contention avoidance mechanism is similar to the one
> used in show_smaps_rollup().
> 
> Signed-off-by: Song Liu <songliubraving@...com>

Acked-by: Yonghong Song <yhs@...com>