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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hYPbaeHa; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="hYPbaeHa" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0FB01F000E9; Wed, 27 May 2026 08:06:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779869177; bh=sjcScadNLsm8B0Y2dlIK5Y/U4/3PKeOfLAFi96a9uPM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hYPbaeHaJO2A3w+tgdZxfJ9EFPIUp8WLKx3Z73CD1knxGldp8Rjyr9x8OH+155xeZ wQ6/hLsLViXBiGGaYdxyiPfr2YmS/8dTfILjbGJdXuZiQGx96tx/0dsahjjP8KP+z0 zw6e/0bncfIFF0acCLEZl6KJ+E1PPNhxMuwkeQ+xKKi/jk+4XlDHp0TcqqHwvy/6FL RvbPp7luBOHEixReRWkh8oibRxkwSvsazaAg/IS7n53iYHBIicyGaafchlWnnOqJnL UCgzhtb95S2dMNkB5YgKgZJ7eiAUHWHbbr04zwpg2Q8Ped1bGIORxnv8sdGmus9Qsn SSYSU0o9bL21w== Message-ID: <8c5bf213-399b-4fa1-835a-36d906061e88@kernel.org> Date: Wed, 27 May 2026 10:06:13 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] mm/slub: use empty sheaf helpers for oversized sheaves Content-Language: en-US To: hu.shengming@zte.com.cn, harry@kernel.org, akpm@linux-foundation.org Cc: hao.li@linux.dev, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, zhang.run@zte.com.cn, cai.qu@zte.com.cn References: <20260526232429176aHA6oZjTYdhXcZVHc2ZQ-@zte.com.cn> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/26/26 17:24, hu.shengming@zte.com.cn wrote: > From: Shengming Hu > > Oversized prefilled sheaves are allocated separately, but after they are > flushed they are empty sheaves as well. Release them through > free_empty_sheaf() instead of calling kfree() directly. > > Use __alloc_empty_sheaf() for oversized prefilled sheaves as well, so > that they are allocated through the same helper as regular empty sheaves > and released through the matching helper. > > Since oversized sheaves are now allocated and freed through the empty > sheaf helpers, SHEAF_ALLOC and SHEAF_FREE also account for oversized > sheaves. Update the stat comments accordingly. > > This keeps the oversized and pfmemalloc prefill paths consistent after > flushing. > > Signed-off-by: Shengming Hu Hmm, __alloc_empty_sheaf() does "gfp &= ~OBJCGS_CLEAR_MASK" which includes __GFP_NOFAIL. A caller of kmem_cache_prefill_sheaf() with __GFP_NOFAIL might not expect failure. The __GFP_NO_OBJ_EXT handling is also not necessary for prefilled sheaves. Well maybe all the gfp handling could be simply moved to alloc_empty_sheaf()? The other caller of __alloc_empty_sheaf() is bootstrap_cache_sheaves() and I think it doesn't need it either. > --- > Changes in v2: > - Rework the change as suggested by Harry. > - Teach __alloc_empty_sheaf() to initialize capacity and pfmemalloc. > - Allocate oversized prefilled sheaves through __alloc_empty_sheaf(). > - Free flushed oversized and pfmemalloc sheaves through free_empty_sheaf(). > - Link to v1: https://lore.kernel.org/all/20260521195015105Y4zvKHj0TfPZEujixy9Vo@zte.com.cn/ > > Changes in v3: > - Address Hao's comments: > - Drop the redundant `pfmemalloc` initialization in > __alloc_empty_sheaf(). > - Keep initializing `capacity` and `pfmemalloc` in the normal-sized > prefill path, since the sheaf may be reused rather than freshly > allocated. > - Link to v2: https://lore.kernel.org/all/20260522145900248m-nBcy07_SCDk2ATDWfmg@zte.com.cn/ > > Changes in v4: > - Address comments from Hao and Harry: > - Keep capacity initialization in the oversized prefill path. > - Update SHEAF_ALLOC and SHEAF_FREE comments to mention oversized sheaves. > - Restore the oversized sheaf pfmemalloc comment. > - Link to v3: https://lore.kernel.org/all/20260525211000387LYqTHmxYL900XIB8qwV3h@zte.com.cn/ > > --- > mm/slub.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 04692a6f9128..08812de7a8b5 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -362,8 +362,8 @@ enum stat_item { > CMPXCHG_DOUBLE_FAIL, /* Failures of slab freelist update */ > SHEAF_FLUSH, /* Objects flushed from a sheaf */ > SHEAF_REFILL, /* Objects refilled to a sheaf */ > - SHEAF_ALLOC, /* Allocation of an empty sheaf */ > - SHEAF_FREE, /* Freeing of an empty sheaf */ > + SHEAF_ALLOC, /* Allocation of an empty sheaf including oversized ones */ > + SHEAF_FREE, /* Freeing of an empty sheaf including oversized ones */ > BARN_GET, /* Got full sheaf from barn */ > BARN_GET_FAIL, /* Failed to get full sheaf from barn */ > BARN_PUT, /* Put full sheaf to barn */ > @@ -5015,12 +5015,11 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size) > > if (unlikely(size > s->sheaf_capacity)) { > > - sheaf = kzalloc_flex(*sheaf, objects, size, gfp); > + sheaf = __alloc_empty_sheaf(s, gfp, size); > if (!sheaf) > return NULL; > > stat(s, SHEAF_PREFILL_OVERSIZE); > - sheaf->cache = s; > sheaf->capacity = size; > > /* > @@ -5029,7 +5028,7 @@ kmem_cache_prefill_sheaf(struct kmem_cache *s, gfp_t gfp, unsigned int size) > */ > if (!__kmem_cache_alloc_bulk(s, gfp, size, > &sheaf->objects[0])) { > - kfree(sheaf); > + free_empty_sheaf(s, sheaf); > return NULL; > } > > @@ -5097,7 +5096,7 @@ void kmem_cache_return_sheaf(struct kmem_cache *s, gfp_t gfp, > if (unlikely((sheaf->capacity != s->sheaf_capacity) > || sheaf->pfmemalloc)) { > sheaf_flush_unused(s, sheaf); > - kfree(sheaf); > + free_empty_sheaf(s, sheaf); > return; > } >