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From: Karthikeyan KS <karthiproffesional@gmail.com>
To: Sang-Heon Jeon <ekffu200098@gmail.com>
Cc: SJ Park <sj@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	damon@lists.linux.dev, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/damon: reject zero sampling interval
Date: Thu, 17 Sep 2026 18:00:13 +0000	[thread overview]
Message-ID: <20260917180013.1279018-1-karthiproffesional@gmail.com> (raw)
In-Reply-To: <CABFDxMHjbQhzvrQmRjo_F9Tf0_zQ20FxaSHFEQN8nfN+VgsF2Q@mail.gmail.com>

Hi Sang-Heon, Hi SJ,

> I think SJ already commented on a similar patch. please refer to [1]
>
> [1] https://lore.kernel.org/all/20260722094304.3132750-1-dayou5941@163.com/

Thanks, missed that thread. Same objection applies to mine.

> Can't we keep supporting zero sample interval and fix the warning
> or the real bug instead?

I measured a few floors for kdamond_usleep():

  floor    kdamond CPU (3s)   vs sample_us=5000
  1us      84%                28x
  100us    42%                14x
  1000us   12%                ~3x
  5000us   ~2%                1x (matches control)

5000us is damon_new_ctx()'s own default, and at that floor the spin
is just gone.

Would you rather we just document sample_us=0 as accepted/expected
behavior, or clamp it to that default inside damon_set_attrs()?

Thanks,
Karthikeyan KS

  reply	other threads:[~2026-09-17 18:00 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-17 15:06 Karthikeyan KS
2026-09-17 16:09 ` Sang-Heon Jeon
2026-09-17 18:00   ` Karthikeyan KS [this message]
2026-09-18  2:38     ` SeongJae Park
2026-09-18 13:13       ` [PATCH v2] mm/damon: document that a zero sample_interval is accepted Karthikeyan KS
2026-09-18 13:35         ` SJ Park
2026-09-18 17:07           ` Karthikeyan KS

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