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Received: from 30.97.56.55(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0W12cKo1_1708657008) by smtp.aliyun-inc.com; Fri, 23 Feb 2024 10:56:49 +0800 Message-ID: <0a06dc7f-3a49-42ba-8221-0b4a3777ac0b@linux.alibaba.com> Date: Fri, 23 Feb 2024 10:56:48 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/3] mm: hugetlb: make the hugetlb migration strategy consistent To: Oscar Salvador 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 References: <0514e5139b17ecf3cd9e09d86c93e586c56688dc.1708507022.git.baolin.wang@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: AE7391A0019 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: 5nb65i5sks9ug6s6zpy79jbb8kkjoahw X-HE-Tag: 1708657017-355194 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 2024/2/23 06:15, Oscar Salvador wrote: > 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: Thanks for reviewing. >> } >> 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? I previously considered passing the MR_reason argument to the htlb_modify_alloc_mask(), which is only used by hugetlb migration. But in alloc_hugetlb_folio_nodemask(), if there are available hugetlb on other nodes, we should allow migrating, that will not break the per-node hugetlb pool. That's why I just change the gfp_mask for allocating a new hguetlb when migration, that can break the pool. struct folio *alloc_hugetlb_folio_nodemask(struct hstate *h, int preferred_nid, nodemask_t *nmask, gfp_t gfp_mask) { spin_lock_irq(&hugetlb_lock); if (available_huge_pages(h)) { struct folio *folio; folio = dequeue_hugetlb_folio_nodemask(h, gfp_mask, preferred_nid, nmask); if (folio) { spin_unlock_irq(&hugetlb_lock); return folio; } } ......