From: SeongJae Park <sj@kernel.org>
To: Josh Law <objecting@objecting.org>
Cc: SeongJae Park <sj@kernel.org>,
akpm@linux-foundation.org, damon@lists.linux.dev,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/2] mm/damon/core: eliminate hot-path integer division in damon_max_nr_accesses()
Date: Mon, 23 Mar 2026 07:10:36 -0700 [thread overview]
Message-ID: <20260323141037.80243-1-sj@kernel.org> (raw)
In-Reply-To: <20260322214325.260007-3-objecting@objecting.org>
On Sun, 22 Mar 2026 21:43:25 +0000 Josh Law <objecting@objecting.org> wrote:
> Hardware integer division is slow. The function damon_max_nr_accesses(),
> which is called very frequently (e.g., once per region per sample
> interval inside damon_update_region_access_rate), performs an integer
> division: attrs->aggr_interval / attrs->sample_interval.
>
> However, the struct damon_attrs already caches this exact ratio in the
> internal field aggr_samples (since earlier commits). We can eliminate
> the hardware division in the hot path by simply returning aggr_samples.
>
> This significantly reduces the CPU cycle overhead of updating the access
> rates for thousands of regions.
>
> Signed-off-by: Josh Law <objecting@objecting.org>
Reviewed-by: SeongJae Park <sj@kernel.org>
Thanks,
SJ
[...]
next prev parent reply other threads:[~2026-03-23 14:10 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-22 21:43 [PATCH v3 0/2] mm/damon/core: Performance optimizations for the kdamond hot path Josh Law
2026-03-22 21:43 ` [PATCH v3 1/2] mm/damon/core: optimize kdamond_apply_schemes() by inverting scheme and region loops Josh Law
2026-03-23 14:07 ` SeongJae Park
2026-03-22 21:43 ` [PATCH v3 2/2] mm/damon/core: eliminate hot-path integer division in damon_max_nr_accesses() Josh Law
2026-03-23 14:10 ` SeongJae Park [this message]
2026-03-24 7:19 ` SeongJae Park
2026-03-24 7:22 ` Josh Law
2026-03-23 14:06 ` [PATCH v3 0/2] mm/damon/core: Performance optimizations for the kdamond hot path SeongJae Park
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