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Thu, 22 Feb 2024 22:14:32 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id liI/AkjH12XxQQAAn2gu4w (envelope-from ); Thu, 22 Feb 2024 22:14:32 +0000 Date: Thu, 22 Feb 2024 23:15:39 +0100 From: Oscar Salvador To: Baolin Wang Cc: akpm@linux-foundation.org, muchun.song@linux.dev, david@redhat.com, linmiaohe@huawei.com, naoya.horiguchi@nec.com, mhocko@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 2/3] mm: hugetlb: make the hugetlb migration strategy consistent Message-ID: References: <0514e5139b17ecf3cd9e09d86c93e586c56688dc.1708507022.git.baolin.wang@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0514e5139b17ecf3cd9e09d86c93e586c56688dc.1708507022.git.baolin.wang@linux.alibaba.com> X-Stat-Signature: ca58ps4znbocmddrpmzaqcqoiq53r1a7 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 582571C0007 X-Rspam-User: X-HE-Tag: 1708640074-763754 X-HE-Meta: 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 pJgv5H9b LA0yvAreva+Mc2vg34YsyIrpBDxSfTQGAAwBsOHO7SKlWjwoULFCYDXFUe83CMmhzUjXPMdPA+fIiqxEdMv7FU7IqFPAEj9tIBzMF6zKBT9asZfUK0PnbPd1IwseWQqePHESQpIVWWLriGnX9e5VT3Ly7A1U775Ua5yPhFPuJXo7qlH2+ebztA37ZwLIEuzp4tJQzzY5qzLciKtY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Feb 21, 2024 at 05:27:54PM +0800, Baolin Wang wrote: > Based on the analysis of the various scenarios above, determine whether fallback is > permitted according to the migration reason in alloc_hugetlb_folio_nodemask(). Hi Baolin, The high level reasoning makes sense to me, taking a step back and thinking about all cases and possible outcomes makes sense to me. I plan to look closer, but I something that caught my eye: > } > spin_unlock_irq(&hugetlb_lock); > > + if (gfp_mask & __GFP_THISNODE) > + goto alloc_new; > + > + /* > + * Note: the memory offline, memory failure and migration syscalls can break > + * the per-node hugetlb pool. Other cases can not allocate new hugetlb on > + * other nodes. > + */ > + switch (reason) { > + case MR_MEMORY_HOTPLUG: > + case MR_MEMORY_FAILURE: > + case MR_SYSCALL: > + case MR_MEMPOLICY_MBIND: > + allowed_fallback = true; > + break; > + default: > + break; > + } > + > + if (!allowed_fallback) > + gfp_mask |= __GFP_THISNODE; I think it would be better if instead of fiddling with gfp here, have htlb_alloc_mask() have a second argument with the MR_reason, do the switch there and enable GFP_THISNODE. Then alloc_hugetlb_folio_nodemask() would already get the right mask. I think that that might be more clear as it gets encapsulated in the function that directly gives us the gfp. Does that makes sense? -- Oscar Salvador SUSE Labs