From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DAA7E3CB8EF for ; Fri, 10 Jul 2026 09:54:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783677291; cv=none; b=o5yY+r6xdtA3/tM65dKj/e3Hgq6ppkEDBGLnW6BAZWKS+R6NS8gGHF6E3xqARmIGldF0BPpFGATtYJGhVF5U80CPYwmiytiiU6kEXKeoa5noovVJS9x69zYT4/AHkejdEP6gz5GEAPmOPoLJE8BNZd5p3fdPhJt5XvDq3h9NDPA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783677291; c=relaxed/simple; bh=+tcDRuJVZvTABXxCs/fekaJDA6k/F5PKtIuIYTGHTgI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Onq1nPZHo3CxYcMaCAnPJzfUPCxio2KmoUud9yYbkxnljX03fRPowwgsgIZqN2rMgA9hnSO/z6ofMAn2yql2ApYcIOphaEqkMkKpzV+qjzaDPYBBtKQSxHRHa924ba0n2yqZFhcp678dM/POBC0j5vJ+ADq0aMm1nvGadiZamVU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E21ryJ6k; 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="E21ryJ6k" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69B911F000E9; Fri, 10 Jul 2026 09:54:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783677289; bh=Luiq+rufALoz7TWFSsrdQQTUMr5CjG0YobeBAejEP2g=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=E21ryJ6k7ZRC/x3HnIYXKjJb8pZyISGJTauG+sNaEBXAExCjFbvq8Ui3wU6cMAA8+ YaFn3EfkB6+DhJY6nhHVFyHBh9whFH1Tc6iFrCat1alfztO0ZRsl7chen+QtrA8vM5 +7igdmHey2TR56QjM2S+WASF+UoSZvf0usAupuL3SzbxsJSPt/tQNcmSPDTR4l9/KC DjjJRSKW8UvGi8tklxTvI/yi5ZyIB82PZl7hzk7I7Wz/Pb8W4Ochw04j3iepVTUbX6 uvOay1rKPnsPbvBytSwn7/LqFmUlUlLkYcC5Dv4tOIvgeXAVhLzZgLQ9g+/+woepcd Ai4KLYdxajk7g== Message-ID: Date: Fri, 10 Jul 2026 11:54:45 +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] mm/slab: extract __free_to_pcs_batch() from free_to_pcs_bulk() Content-Language: en-US To: Hao Li Cc: Harry Yoo , Andrew Morton , Shengming Hu , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260707-slab-simplify-bulk-pcs-v1-1-4850dbe0d904@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/10/26 07:21, Hao Li wrote: > On Fri, Jul 10, 2026 at 01:18:25PM +0800, Hao Li wrote: >> On Tue, Jul 07, 2026 at 02:16:00PM +0200, Vlastimil Babka (SUSE) wrote: >> > It has been noted that free_to_pcs_bulk() is difficult to follow, with a >> > number of goto labels, and this has contributed to two memory leak bugs >> > in there. >> > >> > Extract part of the code to __free_to_pcs_batch(), which focuses only on >> > freeing free-hook-processed local objects to a percpu sheaf, and >> > returning how many were freed. Zero means a trylock failure or no empty >> > sheaf available, and thus the caller should fallback to >> > __kmem_cache_free_bulk(). >> > >> > Make free_to_pcs_bulk() call this in a while loop, removing all goto >> > labels from the function. __free_to_pcs_batch() retains two rather >> > straightforward ones. >> > >> > Signed-off-by: Vlastimil Babka (SUSE) >> >> Nice simplification! >> >> [...] >> > +/* >> > + * Bulk free objects to the percpu sheaves. >> > + * Unlike free_to_pcs() this includes the calls to all necessary hooks >> > + * and the fallback to freeing to slab pages. >> > + */ >> > +static void free_to_pcs_bulk(struct kmem_cache *s, size_t size, void **p) >> > +{ >> > + bool init = slab_want_init_on_free(s); >> > + void *remote_objects[PCS_BATCH_MAX]; >> > + unsigned int remote_nr = 0; >> > + >> > + for (unsigned int i = 0; i < size;) { >> > + struct slab *slab = virt_to_slab(p[i]); >> > + >> > + memcg_slab_free_hook(s, slab, p + i, 1); >> > + alloc_tagging_slab_free_hook(s, slab, p + i, 1); >> > + >> > + if (unlikely(!slab_free_hook(s, p[i], init, false))) { >> > + p[i] = p[--size]; >> > + continue; >> > + } >> > + >> > + if (unlikely(!can_free_to_pcs(slab))) { >> > + remote_objects[remote_nr] = p[i]; >> > + p[i] = p[--size]; >> > + if (++remote_nr >= PCS_BATCH_MAX) { >> > + __kmem_cache_free_bulk(s, remote_nr, &remote_objects[0]); >> > + stat_add(s, FREE_SLOWPATH, remote_nr); >> > + remote_nr = 0; >> > + } >> > + continue; >> > + } >> > + >> > + i++; >> > } >> > >> > - if (remote_nr) >> > - goto flush_remote; >> > + while (size) { >> > + unsigned int batch_freed = __free_to_pcs_batch(s, size, p); >> > >> > - return; >> > + if (!batch_freed) >> > + break; >> > >> > -no_empty: >> > - local_unlock(&s->cpu_sheaves->lock); >> > + p += batch_freed; >> > + size -= batch_freed; >> > + } >> > >> > - /* >> > - * if we depleted all empty sheaves in the barn or there are too >> > - * many full sheaves, free the rest to slab pages >> > - */ >> > -fallback: >> > - __kmem_cache_free_bulk(s, size, p); >> > - stat_add(s, FREE_SLOWPATH, size); >> > + if (size) { >> > + __kmem_cache_free_bulk(s, size, p); >> > + stat_add(s, FREE_SLOWPATH, size); >> > + } >> >> By the way, could we move this directly into the loop inside the >> `if (!batch_freed)` block to make it a bit more concise? but it's totally fine >> to leave it as is! :) Ah right, great suggestion! will do. > oops, forgot to add the r-b tag just now :P > > Reviewed-by: Hao Li Thanks! >> >> > >> > -flush_remote: >> > if (remote_nr) { >> > __kmem_cache_free_bulk(s, remote_nr, &remote_objects[0]); >> > stat_add(s, FREE_SLOWPATH, remote_nr); >> > >> > --- >> > base-commit: 72bb229f9161a1efcd5df32141b69fcc6ae81a13 >> > change-id: 20260707-slab-simplify-bulk-pcs-a8d0478feef6 >> > >> > Best regards, >> > -- >> > Vlastimil Babka (SUSE) >> > >