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 9CA0A346A1D; Thu, 16 Jul 2026 15:08:05 +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=1784214486; cv=none; b=dc90ag+nNQMYitRTyvfayBCRYCnrUyny+dUpnHKtrFlkD7ysQXQKOq9fJXrIo99GQ/16p3KqjboOkCsZLv9eX4RwZDQvmCi6GxFlZEckOmKZSXiK3xlazBivITe9PsIbU2paX2ut7P0Yayt5j9W0jrn8nacgLyFBI/ebAW5DyDs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784214486; c=relaxed/simple; bh=NUc8EizNIfEwE2KLFoAnxARrKDQi7kCpbQSCkz7LyQk=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kYlZBHyXn9YLSYbuszx9933EnnY7jdzijO2pL04mWWB8eCqGf6LPFtQLGaLY5MPJmolBp++u0Ukzb/Jkmo1J1cH2zmHAoSEca/85b1QYbCZFPn5t8NuNiDGILFkERGYtbaAnf8byK3BGq1KoVndvuv3vPjBA0NTLzkivbhCIrd0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fKMMmzgD; 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="fKMMmzgD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0FCA1F00A3A; Thu, 16 Jul 2026 15:08:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784214485; bh=noEZ6+2cpB7DuHX7F4CYxQYpyejbPopCH8uJ2lKswiw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=fKMMmzgD8UZAY4iQDNzHsoe/vm62FJ8khvmHljKlL+8k75A8GjRKAIn6MxudSwOUc vHot8rNwI2vg53sgSyhGIYosr7n0Rlje8aG0MY/sPJh3bTMrzho8hN+4dErmvffD7D cq0FMFsXL9W1mLRSQ3UnyxIN/3E0oNP5b05tKLJ3zZzX1+5Qzu9a6z2oWqci1Cah0e DPjHAfrR+PWcfNifWNbVRkvz+r26Us9sLjTUH3aMr3nyCp4613zqvLVP6fsr+OtRLB z7P60p8v64kv+j/P8AEXSdaFJ+1t8aimnb108Fbix2cfryCHs9nudMfOxH2yYrwP/Y 3y9/J0YyqjMnA== Message-ID: Date: Thu, 16 Jul 2026 17:08:00 +0200 Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 12/12] mm/slab: stop allocating objcg pointers when unnecessary Content-Language: en-US To: Suren Baghdasaryan Cc: Harry Yoo , Hao Li , Shakeel Butt , Alexander Potapenko , Marco Elver , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org References: <20260715-b4-objext_split-v1-0-9a49c4ccf4c3@kernel.org> <20260715-b4-objext_split-v1-12-9a49c4ccf4c3@kernel.org> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/16/26 06:46, Suren Baghdasaryan wrote: > Maybe now we should rename static_obj_ext_size() to > static_obj_ext_max_size() as it reflects the max possible size of > slabobj_ext? Hm with _max_size() it doesn't have to be called static_ anymore? But maybe we can get rid of it completely. The only caller is calculate_sizes(): #if defined(CONFIG_SLAB_OBJ_EXT) && defined(CONFIG_64BIT) if (slab_args_unmergeable(args, s->flags) && (aligned_size - size >= static_obj_ext_size())) s->flags |= SLAB_OBJ_EXT_IN_OBJ; #endif We don't have slab pointer to pass to static_obj_ext_max_size(). But we should be able to figure it out from the cache via cache_needs_objcg(). So we'd need cache_obj_ext_size()? The static max size here works, but may prevent SLAB_OBJ_EXT_IN_OBJ needlessly if padding can only fit codetag_ref and not objcg, but we don't need objcg. Which is probably only theoretical at this point as kmalloc_normal caches (that have no objcg) have no padding, at least without slab_debug. But still. >> + size_t sz = 0; >> + >> + if (slab_needs_objcg(slab)) >> + sz += 1; >> + >> + if (slab_obj_ext_has_codetag()) >> + sz += 1; >> + >> + return sizeof(struct slabobj_ext) * sz; >> } >> >> #ifdef CONFIG_SLAB_OBJ_EXT >> @@ -741,7 +749,7 @@ static inline struct obj_cgroup **slab_obj_ext_objcgp(struct slabobj_ext *obj_ex >> static inline union codetag_ref * >> slab_obj_ext_codetag_ref(struct slab *slab, struct slabobj_ext *obj_ext) >> { >> - if (IS_ENABLED(CONFIG_MEMCG)) >> + if (slab_needs_objcg(slab)) >> obj_ext += 1; >> >> return &obj_ext->_ctref; >> diff --git a/mm/slub.c b/mm/slub.c >> index 771d73abacb6..09c4931e5435 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -2503,6 +2503,9 @@ void memcg_slab_free_hook(struct kmem_cache *s, struct slab *slab, void **p, >> if (likely(!obj_exts)) >> return; >> >> + if (!slab_needs_objcg(slab)) >> + return; >> + >> get_slab_obj_exts(obj_exts); >> __memcg_slab_free_hook(s, slab, p, objects, obj_exts); >> put_slab_obj_exts(obj_exts); >> >> -- >> 2.55.0 >>