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Tue, 6 Jan 2026 10:38:45 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id lL34CzXmXGmDJwAAD6G6ig (envelope-from ); Tue, 06 Jan 2026 10:38:45 +0000 Message-ID: Date: Tue, 6 Jan 2026 11:38:44 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v2 2/3] mm/page_alloc: refactor the initial compaction handling Content-Language: en-US To: Joshua Hahn Cc: Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , David Rientjes , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20251222074055.74545-1-joshua.hahnjy@gmail.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20251222074055.74545-1-joshua.hahnjy@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0C52320004 X-Stat-Signature: dienux3ei1r7ofoxtbhp4meyhtaetyze X-Rspam-User: X-HE-Tag: 1767695926-263967 X-HE-Meta: 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 p3BkLJ+d El6C8kGZbvI84Z9QtbuIHqQGY7PR0xd14PHoO5Odx+hyORhpzkVsUYl4b+Cv0ANClVcRXbFQW4ms5KklYGZ+DV7BbxxSVTUdiiPtLbFED3B79VECTeaB6pPu91j1pESNasmSVDBJom4itYXfvoIr6h13VvBI+j1Ftmdeq6aZWVGhzrQEOOpq8c1joPMUV5sB2++U/klIqgW9/QEc6F44aL7k80kGL3aqkosQt2Z4rncxr984Krq2XcwfhRKYJU28ImFw2jTANKSt45EDLMdcTrc2epvy4gd4yT6y2E95PZCmAHMaVvMd3pYusrogZ6jFIHw2Lxgpfn/E8DDsPfD1x6xBVTNviiHZY4pWJu/mcAxyYQ+O6modRz6xg7oroHazvZCp67iC1rCAhF6fvkd4lSRhaImiZ4KjY0Ny0pUe8Jfc0lbnZXf4jUhEKaSnwpreCfsQxkGD2mKRZMmxcbcLFV7DdvZHhnjfjrxM8RIn0nnzCIZc= 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 12/22/25 08:40, Joshua Hahn wrote: > On Fri, 19 Dec 2025 18:38:52 +0100 Vlastimil Babka wrote: > > Hi Vlastimil, > > I hope you are doing well, sorry for the late reply. The patch overall looks > good to me, but I have a few very small nits. > >> The initial direct compaction done in some cases in >> __alloc_pages_slowpath() stands out from the main retry loop of >> reclaim + compaction. >> >> We can simplify this by instead skipping the initial reclaim attempt via >> a new local variable compact_first, and handle the compact_prority to >> match the original behavior. >> >> Suggested-by: Johannes Weiner >> Signed-off-by: Vlastimil Babka >> --- >> mm/page_alloc.c | 106 +++++++++++++++++++++++++++++--------------------------- >> 1 file changed, 54 insertions(+), 52 deletions(-) >> >> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >> index 9e7b0967f1b5..cb8965fd5e20 100644 >> --- a/mm/page_alloc.c >> +++ b/mm/page_alloc.c >> @@ -4512,6 +4512,11 @@ static bool oom_reserves_allowed(struct task_struct *tsk) >> return true; >> } >> >> +static inline bool gfp_thisnode_noretry(gfp_t gfp_mask) >> +{ >> + return (gfp_mask & __GFP_NORETRY) && (gfp_mask & __GFP_THISNODE); >> +} > > NIT: Is there a reason why this was turned into its own function? The checks > seem short enough to open-code and it seems like there's only one caller as > far as I can tell. Actually I think there are some better candidates of > turning boolean checks into functions, like the one below: I initially made the helper because there were multiple uses of it but then went away with the refactoring. Agree it's not useful at this point. > [...snip...] > >> + /* >> + * For costly allocations, try direct compaction first, as it's likely >> + * that we have enough base pages and don't need to reclaim. For non- >> + * movable high-order allocations, do that as well, as compaction will >> + * try prevent permanent fragmentation by migrating from blocks of the >> + * same migratetype. >> + */ >> + if (can_compact && (costly_order || (order > 0 && >> + ac->migratetype != MIGRATE_MOVABLE))) { >> + compact_first = true; >> + compact_priority = INIT_COMPACT_PRIORITY; >> + } >> + > > It has indeed become shorter thanks to this patch, but I think if we want to > make the code more "readable" we can stay consistent and move these into thier > own boolean checks, or just leave them open-coded. No strong preference here, > just wanted to offer my 2c and hear what you think. Yeah I'll leave the open coded variants, as with single usages the wrappers would just add another layer to go through when trying to understand the code. > [...snip...] > >> + /* >> + * For the initial compaction attempt we have lowered its >> + * priority. Restore it for further retries. With __GFP_NORETRY >> + * there will be a single round of reclaim+compaction with the >> + * lowered priority. >> + */ >> + if (!(gfp_mask & __GFP_NORETRY)) { >> + compact_priority = DEF_COMPACT_PRIORITY; >> + } > > NIT: I think these braces are unecessary : -) Ack. > Otherwise, LGTM! Thank you for your work, it looks a lot cleaner. > > Reviewed-by: Joshua Hahn Thanks!