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t=1754438392; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5JL8jnvobkbM4VKc+fVw+a16FXpkbfBu4M8aK71Ytww=; b=dFxElsnuKJfruwc6WX1SCi+Y0y4YHzUkBOZs/gsX7n9cB9PGI/YBUggLR03dEhQLWSutqC a2LdHALMyaILTrYJSUi2NV2LMfHiWz41Fhvd7NTagnHAlEy/Siij6TqhW/FJKoJ1XzGDC0 TBnle9fg2qaQFrssgvV8a6+J2Fg+23g= X-AuditID: a67dfc5b-669ff7000002311f-02-68929af3b516 Date: Wed, 6 Aug 2025 08:59:41 +0900 From: Byungchul Park To: Joshua Hahn Cc: Andrew Morton , David Hildenbrand , SeongJae Park , Ying Huang , Alistair Popple , Gregory Price , Matthew Brost , Rakie Kim , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, kernel_team@skhynix.com Subject: Re: [PATCH v3] mempolicy: Clarify what zone reclaim means Message-ID: <20250805235941.GA53923@system.software.com> References: <20250805205048.1518453-1-joshua.hahnjy@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; 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Contrary to its user-facing name, it is internally referred to as > "node_reclaim_mode". > > This can be confusing. But because we cannot change the name of the API since > it has been in place since at least 2.6, let's try to be more explicit about > what the behavior of this API is. > > Change the description to clarify what zone reclaim entails, and be explicit > about the RECLAIM_ZONE bit, whose purpose has led to some confusion in the > past already [1] [2]. > > While at it, also soften the warning about changing these bits. > > [1] https://lore.kernel.org/linux-mm/1579005573-58923-1-git-send-email-alex.shi@linux.alibaba.com/ > [2] https://lore.kernel.org/linux-mm/20200626003459.D8E015CA@viggo.jf.intel.com/ > > Acked-by: SeongJae Park > Acked-by: David Hildenbrand > Reviewed-by: Huang Ying > Signed-off-by: Joshua Hahn > --- > v2 --> v3: > - Fixed typos > - Softend wording from "never" --> "should not" > > include/uapi/linux/mempolicy.h | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/include/uapi/linux/mempolicy.h b/include/uapi/linux/mempolicy.h > index 1f9bb10d1a47..683c130782f0 100644 > --- a/include/uapi/linux/mempolicy.h > +++ b/include/uapi/linux/mempolicy.h > @@ -66,10 +66,16 @@ enum { > #define MPOL_F_MORON (1 << 4) /* Migrate On protnone Reference On Node */ > > /* > + * Enabling zone reclaim means the page allocator will attempt to fulfill > + * the allocation request on the current node by triggering reclaim and > + * trying to shrink the current node. > + * Fallback allocations on the next candidates in the zonelist are considered > + * when reclaim fails to free up enough memory in the current node/zone. I was confused too, at the beginning. Thanks for the explicit comment. Acked-by: Byungchul Park Byungchul > + * > * These bit locations are exposed in the vm.zone_reclaim_mode sysctl > - * ABI. New bits are OK, but existing bits can never change. > + * ABI. New bits are OK, but existing bits should not be changed. > */ > -#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ > +#define RECLAIM_ZONE (1<<0) /* Enable zone reclaim */ > #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ > #define RECLAIM_UNMAP (1<<2) /* Unmap pages during reclaim */ > > > base-commit: 6bcdbd62bd56e6d7383f9e06d9d148935b3c9b73 > -- > 2.47.3