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From: Masami Hiramatsu <mhiramat@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: "wuqiang.matt" <wuqiang.matt@bytedance.com>,
	naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com,
	davem@davemloft.net, mhiramat@kernel.org, mingo@kernel.org,
	peterz@infradead.org, linux-kernel@vger.kernel.org,
	mattwu@163.com
Subject: Re: [PATCH] kretprobe scalability improvement
Date: Mon, 5 Jul 2021 08:59:01 +0900	[thread overview]
Message-ID: <20210705085901.20f97a48c37fdc533d554dc6@kernel.org> (raw)
In-Reply-To: <YOF8fyJIzJmZUhoC@infradead.org>

On Sun, 4 Jul 2021 10:16:47 +0100
Christoph Hellwig <hch@infradead.org> wrote:

> Would it make sense to just reuse kernel/bpf/percpu_freelist.c for
> kretprobes?

Hmm, I don't think so.
It seems that what Wuqiang proposed is more efficient than the 
percpu_freelist, and it will be less efficient from the viewpoint
of memory usage because kretprobe freelist manages instance pool
among all CPUs (which can be unbalanced, sometimes 95% used by one
core, sometimes used evenly).

Actually, the best solution is to have per-task fixed-size instance
pool which is shared by all kretprobes (e.g. 4kb/task), because
the instance makes a "shadow stack" for each task. This may consume
more memory but is not increased by adding kretprobes, and should be
scalable.

Thank you,

-- 
Masami Hiramatsu <mhiramat@kernel.org>

  reply	other threads:[~2021-07-04 23:59 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-03 10:28 wuqiang.matt
2021-07-04  9:16 ` Christoph Hellwig
2021-07-04 23:59   ` Masami Hiramatsu [this message]
2021-07-05  2:50     ` Matt Wu
2021-07-05  6:59 ` Masami Hiramatsu
2021-07-06  1:21   ` Matt Wu
2021-07-06 16:25     ` Masami Hiramatsu
2021-07-07  3:10       ` Matt Wu
2021-07-07 11:26         ` Masami Hiramatsu
2021-07-04 10:18 Matt Wu

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