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Wed, 21 Jan 2026 09:39:12 -0800 (PST) MIME-Version: 1.0 References: <20260116-sheaves-for-all-v3-0-5595cb000772@suse.cz> <20260116-sheaves-for-all-v3-14-5595cb000772@suse.cz> <2tvnelafuozzzfyvmxvflqmx2sepgy7ottnw4n2trkh33rrk6b@oewlapq3smvg> In-Reply-To: <2tvnelafuozzzfyvmxvflqmx2sepgy7ottnw4n2trkh33rrk6b@oewlapq3smvg> From: Suren Baghdasaryan Date: Wed, 21 Jan 2026 17:39:00 +0000 X-Gm-Features: AZwV_Qi3Y2iex4LEenR-glhvYF5fdvLAgmEL3JsgkohqCrj2SiE002EgBpgOZDM Message-ID: Subject: Re: [PATCH v3 14/21] slab: simplify kmalloc_nolock() To: Hao Li Cc: Vlastimil Babka , Harry Yoo , Petr Tesarik , Christoph Lameter , David Rientjes , Roman Gushchin , Andrew Morton , Uladzislau Rezki , "Liam R. Howlett" , Sebastian Andrzej Siewior , Alexei Starovoitov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, bpf@vger.kernel.org, kasan-dev@googlegroups.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam11 X-Stat-Signature: 53ugu6j6o4xkeojthukm81tk1sprbirf X-Rspam-User: X-Rspamd-Queue-Id: 02F7E2001D X-HE-Tag: 1769017153-48306 X-HE-Meta: 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 BtxroUFi mtYW1cnNebHQhjYFwMGqkrt+17NfTeM6Gzl1gZ+0beyFWiR3DZGz/eBZ4So1jIfHLVcWnXtZzXkIL8qxGzaCB8v+HX730Qw2PF259HttcqDdJvfZlZcSNoeWMKmspGsxnAIzE/HCakjIlvkoODmnItJcLVxzd9gDMXzjqJ/U7DiFbURWSJ5Idn++EAfZDI/LvzpbXcOv1NnhCF566+yK3T5FmewFg47Vo8d3USG8Tiin4YARm+7HrkfMJGe6R6bt8QdaJwU+Y/o2TlyoMHZzlp9fNOuGaI6rzyD7CGk69sbliwp5QF4C2EKTSFA== 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 Tue, Jan 20, 2026 at 12:07=E2=80=AFPM Hao Li wrote: > > On Fri, Jan 16, 2026 at 03:40:34PM +0100, Vlastimil Babka wrote: > > The kmalloc_nolock() implementation has several complications and > > restrictions due to SLUB's cpu slab locking, lockless fastpath and > > PREEMPT_RT differences. With cpu slab usage removed, we can simplify > > things: > > > > - relax the PREEMPT_RT context checks as they were before commit > > a4ae75d1b6a2 ("slab: fix kmalloc_nolock() context check for > > PREEMPT_RT") and also reference the explanation comment in the page > > allocator > > > > - the local_lock_cpu_slab() macros became unused, remove them > > > > - we no longer need to set up lockdep classes on PREEMPT_RT > > > > - we no longer need to annotate ___slab_alloc as NOKPROBE_SYMBOL > > since there's no lockless cpu freelist manipulation anymore > > > > - __slab_alloc_node() can be called from kmalloc_nolock_noprof() > > unconditionally. It can also no longer return EBUSY. But trylock > > failures can still happen so retry with the larger bucket if the > > allocation fails for any reason. > > > > Note that we still need __CMPXCHG_DOUBLE, because while it was removed > > we don't use cmpxchg16b on cpu freelist anymore, we still use it on > > slab freelist, and the alternative is slab_lock() which can be > > interrupted by a nmi. Clarify the comment to mention it specifically. > > > > Signed-off-by: Vlastimil Babka > > --- > > mm/slab.h | 1 - > > mm/slub.c | 144 +++++++++++++-----------------------------------------= -------- > > 2 files changed, 29 insertions(+), 116 deletions(-) > > > > Looks good to me. > Reviewed-by: Hao Li Reviewed-by: Suren Baghdasaryan > > -- > Thanks, > Hao