From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D6A372264C0 for ; Fri, 6 Mar 2026 11:39:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772797171; cv=none; b=XAeTcCsqeuAEL2jlN3fJgNmvSEEahlzBJgttzLJZC/Afsfv9YjckFDcsrQzwcIyxrYF+bZOxeSmykL8UKpvUOPae+D4DS5i4WuRCjNRRm0Z3nC+Rt5ZkyJBBBlJ0zxFTo8/TM/nZ5PP4PfaZlaYiR1Mnw0yGbV4x6o0YsEF16gM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772797171; c=relaxed/simple; bh=0cs8qXX0w8L9WzG6FxiKkEtbMe4IWFPc1fUI16tb98U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bXjNoYo5xwcm3CcxWFAETQCILkaeSiHUpmi3UQ5fYBh+HyWtQJurNe4oYCfMbsB7NbzAl4G+wb25qDuYyw9GPRU/eGDnSAZKvjuZWElDSjkHqoT49QwPG73TwEua9ei+4b+y6RnHX/5xuoxVmhc91wPI0WsvJ3nUF1h7IfuapEI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=q6+5bJU5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="q6+5bJU5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DEE6CC4CEF7; Fri, 6 Mar 2026 11:39:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772797171; bh=0cs8qXX0w8L9WzG6FxiKkEtbMe4IWFPc1fUI16tb98U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=q6+5bJU5Q4vnGYIOMHxtP/fwEKuDSK2hA5IhDe8+PkQeYooM2TIRjBnvmFVvCA3id zx+kdnfnhGj/Hc2J46iXwA7kz4D7aKyf8Ka9/QeE1ovFxzsN3ZjpEk/g/ZL9CHq9WO DL7EyjTCNT0rTq3V++Z1Z84TjsutySazmrFPxuph6Vni0biEndWsyaZL539j5TjDKp Gqs9RY0RSWWVsCxDv3rAkXkjlCRjN830b6gyc3TvnCgioA1C0CvyoEpheBCHuDkVyF RN08EbOx/XEUw9Xpfs5pPNDPGwK44ER8hK5YYUNd/Wdd6dIeNoGI0Oo1D9ycyuIAfB 43L0aHB1cxH9Q== Date: Fri, 6 Mar 2026 11:39:28 +0000 From: "Lorenzo Stoakes (Oracle)" To: Breno Leitao Cc: Andrew Morton , David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, usamaarif642@gmail.com, kas@kernel.org, kernel-team@meta.com Subject: Re: [PATCH v2 3/3] mm: huge_memory: refactor enabled_store() with change_enabled() Message-ID: References: <20260305-thp_logs-v2-0-96b3ad795894@debian.org> <20260305-thp_logs-v2-3-96b3ad795894@debian.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260305-thp_logs-v2-3-96b3ad795894@debian.org> On Thu, Mar 05, 2026 at 06:04:55AM -0800, Breno Leitao wrote: > Refactor enabled_store() to use a new change_enabled() helper that > reuses the shared enum enabled_mode and enabled_mode_strings[] > introduced in the previous commit. > > The helper uses the same loop pattern as change_anon_orders(), > iterating over an array of flag bit positions and using > test_and_set_bit()/test_and_clear_bit() to track whether the state > actually changed. ENABLED_INHERIT is rejected since it is not a > valid mode for the global THP setting. > > Signed-off-by: Breno Leitao > --- > mm/huge_memory.c | 51 ++++++++++++++++++++++++++++++++++++--------------- > 1 file changed, 36 insertions(+), 15 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 19619213f54d1..dd5011cf36839 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -330,30 +330,51 @@ static const char * const enabled_mode_strings[] = { > [ENABLED_NEVER] = "never", > }; > > +static bool change_enabled(enum enabled_mode mode) > +{ > + static const unsigned long thp_flags[] = { > + TRANSPARENT_HUGEPAGE_FLAG, > + TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, > + }; > + bool changed = false; > + int i; > + > + for (i = 0; i < ARRAY_SIZE(thp_flags); i++) { > + if (i == mode) > + changed |= !test_and_set_bit(thp_flags[i], > + &transparent_hugepage_flags); > + else > + changed |= test_and_clear_bit(thp_flags[i], > + &transparent_hugepage_flags); > + } > + > + return changed; > +} > + > static ssize_t enabled_store(struct kobject *kobj, > struct kobj_attribute *attr, > const char *buf, size_t count) > { > - ssize_t ret = count; > + int mode; > > - if (sysfs_streq(buf, "always")) { > - clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > - set_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > - } else if (sysfs_streq(buf, "madvise")) { > - clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > - set_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > - } else if (sysfs_streq(buf, "never")) { > - clear_bit(TRANSPARENT_HUGEPAGE_FLAG, &transparent_hugepage_flags); > - clear_bit(TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, &transparent_hugepage_flags); > - } else > - ret = -EINVAL; > + mode = sysfs_match_string(enabled_mode_strings, buf); > + if (mode < 0 || mode == ENABLED_INHERIT) > + return -EINVAL; The mode == ENABLED_INHERIT check is weird, it reads like 'oh a user CAN specify this, but if they do we error out', but in reality /sys/kernel/mm/transparent_hugepage/enabled explicitly outputs only always, inherit, maddvise. So, even though it's duplicative, I think it's probably saner to have: static const char * const anon_enabled_mode_strings[] = { [ENABLED_ALWAYS] = "always", [ENABLED_MADVISE] = "madvise", [ENABLED_INHERIT] = "inherit", [ENABLED_NEVER] = "never", }; static const char * const global_enabled_mode_strings[] = { [ENABLED_ALWAYS] = "always", [ENABLED_MADVISE] = "madvise", [ENABLED_NEVER] = "never", }; Just to make it clear what you're doing. And if you add something for shmem add one for that too. With that fixed, feel free to add: Reviewed-by: Lorenzo Stoakes (Oracle) > > - if (ret > 0) { > + if (change_enabled(mode)) { > int err = start_stop_khugepaged(); > + > if (err) > - ret = err; > + return err; > + } else { > + /* > + * Recalculate watermarks even when the mode didn't > + * change, as the previous code always called > + * start_stop_khugepaged() which does this internally. > + */ > + set_recommended_min_free_kbytes(); > } > - return ret; > + return count; > } > > static struct kobj_attribute enabled_attr = __ATTR_RW(enabled); > > -- > 2.47.3 > Cheers, Lorenzo