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From: Hao Li To: Vlastimil Babka Cc: Harry Yoo , Petr Tesarik , Christoph Lameter , David Rientjes , Roman Gushchin , Andrew Morton , Uladzislau Rezki , "Liam R. Howlett" , Suren Baghdasaryan , 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 Subject: Re: [PATCH v3 07/21] slab: make percpu sheaves compatible with kmalloc_nolock()/kfree_nolock() Message-ID: References: <20260116-sheaves-for-all-v3-0-5595cb000772@suse.cz> <20260116-sheaves-for-all-v3-7-5595cb000772@suse.cz> <008029ff-3fd8-49cf-8aa7-71b98dc15be9@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <008029ff-3fd8-49cf-8aa7-71b98dc15be9@suse.cz> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 2EBB6C000C X-Rspam-User: X-Stat-Signature: ej5owuo5op1oh3cfdwgr9csep64syhet X-HE-Tag: 1768824409-225192 X-HE-Meta: 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 4JkuAhEZ 4A7qqboQjpyn4Wkji0UPDUhEbfP5rbU1jWyWi3e+acuYx8KEXLrraBjn/TL1O8tJdy/i91c9kj4cK1wlWwdTFEHHHPDs74Hfc0ZtHIyiUXdFP/t+9GwrVGxBx2onVz3lAqefBa0Wg/m/nXPw0s70+iJwS4WPkJdb3hDadwvRZPaY1eKGNDxgf88IP/R3lag7Z7i+BfpufTzdR9TfL0w2gtzu/XeQ3HK2sGPf63gaGBrRscSnlLn1gDgQNLmE95m7egrvhnUB2j95hCXHV9iFKeyyyzw== 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 Mon, Jan 19, 2026 at 11:23:04AM +0100, Vlastimil Babka wrote: > On 1/19/26 11:09, Vlastimil Babka wrote: > > On 1/19/26 05:31, Harry Yoo wrote: > >> On Fri, Jan 16, 2026 at 03:40:27PM +0100, Vlastimil Babka wrote: > >>> Before we enable percpu sheaves for kmalloc caches, we need to make sure > >>> kmalloc_nolock() and kfree_nolock() will continue working properly and > >>> not spin when not allowed to. > >>> > >>> Percpu sheaves themselves use local_trylock() so they are already > >>> compatible. We just need to be careful with the barn->lock spin_lock. > >>> Pass a new allow_spin parameter where necessary to use > >>> spin_trylock_irqsave(). > >>> > >>> In kmalloc_nolock_noprof() we can now attempt alloc_from_pcs() safely, > >>> for now it will always fail until we enable sheaves for kmalloc caches > >>> next. Similarly in kfree_nolock() we can attempt free_to_pcs(). > >>> > >>> Signed-off-by: Vlastimil Babka > >>> --- > >> > >> Looks good to me, > >> Reviewed-by: Harry Yoo > > > > Thanks. > > > >> > >> with a nit below. > >> > >>> mm/slub.c | 79 ++++++++++++++++++++++++++++++++++++++++++++------------------- > >>> 1 file changed, 56 insertions(+), 23 deletions(-) > >>> > >>> diff --git a/mm/slub.c b/mm/slub.c > >>> index 706cb6398f05..b385247c219f 100644 > >>> --- a/mm/slub.c > >>> +++ b/mm/slub.c > >>> @@ -6703,7 +6735,7 @@ void slab_free(struct kmem_cache *s, struct slab *slab, void *object, > >>> > >>> if (likely(!IS_ENABLED(CONFIG_NUMA) || slab_nid(slab) == numa_mem_id()) > >>> && likely(!slab_test_pfmemalloc(slab))) { > >>> - if (likely(free_to_pcs(s, object))) > >>> + if (likely(free_to_pcs(s, object, true))) > >>> return; > >>> } > >>> > >>> @@ -6964,7 +6996,8 @@ void kfree_nolock(const void *object) > >>> * since kasan quarantine takes locks and not supported from NMI. > >>> */ > >>> kasan_slab_free(s, x, false, false, /* skip quarantine */true); > >>> - do_slab_free(s, slab, x, x, 0, _RET_IP_); > >>> + if (!free_to_pcs(s, x, false)) > >>> + do_slab_free(s, slab, x, x, 0, _RET_IP_); > >>> } > >> > >> nit: Maybe it's not that common but should we bypass sheaves if > >> it's from remote NUMA node just like slab_free()? > > > > Right, will do. > > However that means sheaves will help less with the defer_free() avoidance > here. It becomes more obvious after "slab: remove the do_slab_free() > fastpath". All remote object frees will be deferred. Guess we can revisit > later if we see there are too many and have no better solution... This makes sense to me, and the commit looks good as well. Thanks! Reviewed-by: Hao Li > > >>> EXPORT_SYMBOL_GPL(kfree_nolock); > >>> > >>> @@ -7516,7 +7549,7 @@ int kmem_cache_alloc_bulk_noprof(struct kmem_cache *s, gfp_t flags, size_t size, > >>> size--; > >>> } > >>> > >>> - i = alloc_from_pcs_bulk(s, size, p); > >>> + i = alloc_from_pcs_bulk(s, flags, size, p); > >>> > >>> if (i < size) { > /* > >>> > >> > > >