From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wr1-f74.google.com (mail-wr1-f74.google.com [209.85.221.74]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6373035CB76 for ; Fri, 20 Mar 2026 09:48:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774000096; cv=none; b=RsolgRa68pxdHLFKMYK8M8fzbJyhylwBaEeoePOh+57dFfSATsHeI+nR3AWniFZDsfRl5IBdA99eghv/Y6+3VPvmdFcRpiISdS5a/9rSwgmbR3O00/reDwW0kWiZBvKU0qGbem5hQDWPbZpsHsa7OUzMiDqd8MfH0sk9By05SnY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774000096; c=relaxed/simple; bh=eTQR5/IgOfx1NHB+3VO9TceGUC0T6aCde0lExdGLsZE=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=fSsiBdwmv+EU1G5snjMJn9kKtpiDyYuc/iU1y0b9+wfZeBqnQG6XiYstpUdB4/Whlf6Jzpj5VItMmCnVEqGpn0+scxyZDJz8HVxpTq0W0yswgh0qJmdN3P6jrgRBBZxMcuhlxxD+IEcd4swHexAvAlXAbW5T4gs9uwWrMEF2c08= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=q2rbUs2C; arc=none smtp.client-ip=209.85.221.74 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="q2rbUs2C" Received: by mail-wr1-f74.google.com with SMTP id ffacd0b85a97d-43b3e0a73f8so1557155f8f.3 for ; Fri, 20 Mar 2026 02:48:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1774000094; x=1774604894; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=mZMrv952vvmsTG9WcEZJ06sxzhgy6LZj415wabLP5nA=; b=q2rbUs2CpE26P5lr4sT1u4etN55E98/Z8L08OLscEJWLV7OVGkfCQyACqQ4m28wRn0 +icL3TPksN3X5sRGEVAh02ou00x4+2ATHPwl2sIhs3XPHajYAUB8wnA8UYcwGq+3rrtc v9et4ph6vVDrbhxORSLbgBxzXZfA5lR54tjmOzNE8FILRJRdJy+jDOO80K7saLuLSVZk i0Ggx3AMBAUj9eUwVRdfqEDM61cHHd3Xa+vn78ihnEqkmx26sSSK3TChfqfiA1DXPo6T 5Y4Dw36QkenCmN3pdw3DtfuMNQmO9lrAJyHyrT/1ULkzwItsgGzdyMP4FJZjqNeTIQz9 kcbw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774000094; x=1774604894; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=mZMrv952vvmsTG9WcEZJ06sxzhgy6LZj415wabLP5nA=; b=VbtJ4wLpG8YlpE/z1BT9JVSDLIuuLGFz0jDtR6he69FzCNuyG/XafnmEjlBq7VJvst YLhxtMxwquA1b1nu3K/kRkmi1wGqDsmjnR1bLCQ4ypgdPi+oYSmlyaznD5RNMnbJLbcL gNDqql7xJ7j7y1F/2mUxoawm/VpOyOnRZNbJVW124i+QkDAYtZoGtCo5qLImouN8kahw I69Wy3KOJhhy55T1vH0lQ4J+y1ZkOF65NaLmzKZKmj/H4sW9bL61hU4eluULIir/Yyjs XlI9+V731pXHgWOhVgnthxuvhzWAZZV2wKumjNv4YiGpr2qIP79puHNTDB+yVvZa1jO3 5bdw== X-Forwarded-Encrypted: i=1; AJvYcCXo4nlJKwNkJUXr2gOHRmvCadUTah4BdW0yhljIIuHaAXNVJVTis2jx3UX75LOa645helHguRIqSRCbOSk=@vger.kernel.org X-Gm-Message-State: AOJu0YyhZowTsxEsOXV76PquJkJZFEw8e47MpzGixan4vNqO8oO9m0ni /VnUXCqcy8V4gX47Gr/6m0AioMGFmsB3/+Mu+k4uN5FMpBCV22g25WLD4VqViM0QGInbBnz7hT+ +5trlB1GYppXg4A== X-Received: from wmlz10.prod.google.com ([2002:a05:600c:220a:b0:485:32b2:6b8d]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:8b18:b0:485:3dfc:57d with SMTP id 5b1f17b1804b1-486ff01ca8dmr31517965e9.30.1774000093379; Fri, 20 Mar 2026 02:48:13 -0700 (PDT) Date: Fri, 20 Mar 2026 09:48:12 +0000 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260319-gfp64-v1-0-2c73b8d42b7f@google.com> X-Mailer: aerc 0.21.0 Message-ID: Subject: Re: [PATCH 0/5] mm: Switch gfp_t to unsigned long From: Brendan Jackman To: Matthew Wilcox , Brendan Jackman , Cc: Andrew Morton , Michal Hocko , David Rientjes , Shakeel Butt , Vlastimil Babka , Suren Baghdasaryan , Johannes Weiner , Zi Yan , Harry Yoo , Hao Li , Christoph Lameter , Roman Gushchin , Uladzislau Rezki , , Content-Type: text/plain; charset="UTF-8" On Thu Mar 19, 2026 at 9:39 PM UTC, Matthew Wilcox wrote: > On Thu, Mar 19, 2026 at 06:40:59PM +0000, Brendan Jackman wrote: >> I will paste the diff at the bottom. I _think_ all the problematic >> expansions are downstream of struct xarray, but it's quite likely my >> sense for problematic struct expansions is weak. > > Urgh, no, it's not all xarray. There's one in address_space which we're > trying to shrink, not grow. Oh sorry I just assumed that one was xa_flags. > There's one in struct sock too. Huh, I suspect I am embarassing myself with this question, but why are we sensitive to the size of struct sock? It's currently 784 bytes in my build. Are the adjacent fields very hot, and we need to look up the GFP flags from hot paths? > I don't think this idea is worth it. There are other projects of greater > or lesser churniess which will give us some flags back. For example, > we could finish the GFP_NOFS and GFP_NOIO removal. We could finish the > radix_tree -> XArray removal and get back three bits. That's five bits > without even starting new projects, just finishing old ones. Anyway, this also makes sense. But, Vlastimil, I guess you had an ulterior motive for this suggestion?