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Howlett" , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, kernel-team@meta.com References: <20260722152043.2273289-1-usama.arif@linux.dev> <20260722152043.2273289-11-usama.arif@linux.dev> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: B972D1C0007 X-Stat-Signature: 151ejb9whi5aoc6iapc77zak4uz5t8yt X-Rspam-User: X-HE-Tag: 1784888862-387343 X-HE-Meta: U2FsdGVkX18REdlgE7z5yKJb4tDEj+e5wP2Z4EQVd8lHbKAXzQ1YvCBrBmVsgxJgiMZi8SN7C9vWk43s5+3m3ZvQ2lIJC8NQ7/cBPLCwTd6f9zKOs3SwA7eBYUGaIT4Qm8SAJNsuO4FNZnUa7EzwfvxQz0EH/NpopN5xaNfX/y8amQ7nY4x62wlIfmhEbGW0gSf7/Pr+izyt8AQTkAC+ZakgsyzJmbGmkSVaZ9GBOiTCa/hXxUwRBSEUtnHzAWOKNc+9TM1Pkn2oquNr+ZxBHo3VlO5b6JPEERa9+mQqRQOUtW4AFsm6dv8vd0wvI97ac3nwDMmplOBXFytkAR5soYf3Q9KbQ1fegiVpuP+TRIw6gkM04SCXYqVYMcIEj99hXXD3EHg/c0Ad7K0PZMRNpzb6N4rT1fMugzkg5xq8mu3vnIUENtFgvPKqba6NPLMXk6Vfx3Yrutr81oGNZB0nBsCCrBNYHqV2fY/zzebvR4sIqTEhYHejTZyNGuEN/oQ/CiNMbRpBYxjg0XFYE3LR4j8OIwpSp4SqW/Sh8kUiHBwumaZ+p9DnYqdziz+2UE3McCstVcl99N8b76BnmSpT4T1t5X6YyYX/cDIGWXiJhQ+E0peiLi0O8MuEQSC/FDQN+P3rxSwL814X0nRdLIuLggNhevdWqKNFj+R2309OCldk3pvTk5QTgoiU/CjwgszhHPYtHmaMNIYUiq9gqcIe7JATLVP0t5aVvqMQ1g3q/dXUhh2HPCqfSVc/icSuxvq3OwtxDi6x5KDWNJSgGc/siDV1wsA+fUxRJCD0VsDVyKE4Ti/+CXfJ7zBrg+wURuxzT0yLHqW52KrrU71MWUIhTmKFo4JW2dY6t3SgkThk6Ds2bsbtNVkDSh9Rp5fU8DM2I49NFFaQwx+u5VUQDe26hTtOtZbvEUIfHBm1Oh5ag0V4K9/vM+MkwvSWqqz/TjNwwQy0O7pd8dJPRHeUSnx eqObcgLr 63tVjX4Kkzs1yop0Af20OTnKCu7uXk5DQ/qnxFLnzMn2uhpLWjqJhccGWq0/gKAlkqjzHoY2k5JMbynUN7h0NtSOZMTxbJ36DpjoVw5l36wQQzWkbjravbTZ6mKl2Fgtdp9NwpVjTmGJXXCyR3TKbDLBrE9NgT53Jr5An+Kuagdv8qw8oHpWr8kciG9P0WwI969gJ2iHoCcOSFsXIyXudnzKjKA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 23/07/2026 20:16, Matthew Wilcox wrote: > On Wed, Jul 22, 2026 at 08:19:41AM -0700, Usama Arif wrote: >> +++ b/mm/rmap.c >> @@ -2282,6 +2282,25 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, >> goto walk_abort; >> } >> >> +#ifdef CONFIG_THP_SWAP >> + /* >> + * If the folio is in the swap cache and we're not >> + * asked to split, install a PMD-level swap entry. >> + */ >> + if (!(flags & TTU_SPLIT_HUGE_PMD) && >> + folio_test_anon(folio) && >> + folio_test_swapcache(folio)) { >> + if (set_pmd_swap_entry(&pvmw, folio)) >> + goto walk_abort; >> + >> + add_mm_counter(mm, MM_ANONPAGES, >> + -HPAGE_PMD_NR); >> + add_mm_counter(mm, MM_SWAPENTS, >> + HPAGE_PMD_NR); >> + goto walk_done; >> + } >> +#endif >> + >> if (flags & TTU_SPLIT_HUGE_PMD) { >> /* >> * We temporarily have to drop the PTL and > > This makes me sad. It feels like we're bolting more complexity onto > try_to_unmap() instead of removing TTU_SPLIT_HUGE_PMD entirely. > > Ideally we'd just cope with folios of whatever size (including > PMD and PUD mapped folios) and only handle hugetlb weirdness when we > absolutely have to. Similarly, we could split PUDs to PMDs and > PMDs to PTEs when we need to, without the caller specifying > TTU_SPLIT_anything. > > Is there a reason we can't do that? I will prototype what the code would look like without TTU_SPLIT_HUGE_PMD and get back to you on this. Looking at the code right now, I feel like I would be shifting complexity, but let me try and do something about this.