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From: Baoquan He To: Youngjun Park Cc: akpm@linux-foundation.org, chrisl@kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kasong@tencent.com, hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, shikemeng@huaweicloud.com, nphamcs@gmail.com, bhe@redhat.com, baohua@kernel.org, gunho.lee@lge.com, taejoon.song@lge.com, hyungjun.cho@lge.com, mkoutny@suse.com, baver.bae@lge.com, matia.kim@lge.com Subject: Re: [PATCH v6 1/4] mm: swap: introduce swap tier infrastructure Message-ID: References: <20260421055323.940344-1-youngjun.park@lge.com> <20260421055323.940344-2-youngjun.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260421055323.940344-2-youngjun.park@lge.com> X-Migadu-Flow: FLOW_OUT X-Stat-Signature: pmcrdi53hj3mp8mr8w47snpgtcwjqrza X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: C23D040004 X-HE-Tag: 1779745769-755690 X-HE-Meta: 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 L7LQYfEb t9GKHg55uO45Mo03NemEJnnYvVKRIrrjOSHBynZxJqlpV8wAqe9ZIB7OUMTIDAM2bKEJh4QjvhP7/MUB+IcDYAk9ODKE6JyKt0KUC0KEQx/d+xqMrbzBbw6J0dh1dYYtvojoq/phy4H+rmNIwjnqCd5v6F/flZfd21gsk3sNWjf3dykTbSUOdzdZ41QUWHUmlr5C7HVbHGSRecTXxgsiPuUgJ/2VUQyA8CWH56u66h1pU9gZ+nqGNR/U72XaQ/ldpzvycHL3QNg/HQXLhR6VElvJ5EEtkRWbAq9MHdyA6JS9Y+tQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 04/21/26 at 02:53pm, Youngjun Park wrote: > This patch introduces the "Swap tier" concept, which serves as an > abstraction layer for managing swap devices based on their performance > characteristics (e.g., NVMe, HDD, Network swap). > > Swap tiers are user-named groups representing priority ranges. > Tier names must consist of alphanumeric characters and underscores. > These tiers collectively cover the entire priority space from -1 > (`DEF_SWAP_PRIO`) to `SHRT_MAX`. > > To configure tiers, a new sysfs interface is exposed at > /sys/kernel/mm/swap/tiers. The input parser evaluates commands from > left to right and supports batch input, allowing users to add or remove > multiple tiers in a single write operation. > > Tier management enforces continuous priority ranges anchored by start > priorities. Operations trigger range splitting or merging, but overwriting > start priorities is forbidden. Merging expands lower tiers upwards to > preserve configured start priorities, except when removing `DEF_SWAP_PRIO`, > which merges downwards. > > Suggested-by: Chris Li > Signed-off-by: Youngjun Park This looks good to me. Reviewed-by: Baoquan He While there's only one tiny concern, please see the inline comment. > diff --git a/mm/swap_tier.c b/mm/swap_tier.c > new file mode 100644 > index 000000000000..9490e891c5fe > --- /dev/null > +++ b/mm/swap_tier.c > @@ -0,0 +1,302 @@ ...... > +/* > + * Naming Convention: > + * swap_tiers_*() - Public/exported functions > + * swap_tier_*() - Private/internal functions > + */ > + > +static bool swap_tier_is_active(void) > +{ > + return !list_empty(&swap_tier_active_list) ? true : false; The above line seems like generated by AI. Whatever else I have seen is "return !list_empty(&swap_tier_active_list);" which is enough. > +} > + ...snip...