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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 2/3] mm: huge_memory: refactor anon_enabled_store() with change_anon_orders() Message-ID: <68156cf9-cf97-4435-b979-c2ab0d6a97b1@lucifer.local> References: <20260305-thp_logs-v2-0-96b3ad795894@debian.org> <20260305-thp_logs-v2-2-96b3ad795894@debian.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260305-thp_logs-v2-2-96b3ad795894@debian.org> X-Rspamd-Queue-Id: BCB8740005 X-Stat-Signature: jwbw1c8xhz3sctufmoeo8w5w4k5p8rcg X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1772796768-98573 X-HE-Meta: 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 COZ6qbxt ljdNW5AOpjztjsWVAmYi90tnyR0c2P0pFYP79kI0U+Vt3Zu4lx9O4LJX0rTz/gD6tmTuzyQR7YyNwF96bCXd44mH4/PyMUvBNBJJ3BFjTDt0dEAajTtGG8xvSE6MZRiMFten1N0ENU3+rTVi6cooFpLDlMXaTuXspRXA4AHBJCec9iiMhqK0DTk/sl7GMlCXiZZQPaHzY4hC4gM241u4yKKYVBtElCtlssNPP8V2EqVzwL7v2v4oUt2sEYDJScr1yYbiklDB9iHFUPHW2bGAp6GnnZyHlwXKfshR/kv2gxISd3/s5uWSFlsZTHQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 05, 2026 at 06:04:54AM -0800, Breno Leitao wrote: > Consolidate the repeated spin_lock/set_bit/clear_bit pattern in > anon_enabled_store() into a new change_anon_orders() helper that > loops over an orders[] array, setting the bit for the selected mode > and clearing the others. > > Introduce enum enabled_mode and enabled_mode_strings[] to be shared > with enabled_store() in a subsequent patch. > > Use sysfs_match_string() with the enabled_mode_strings[] table to > replace the if/else chain of sysfs_streq() calls. > > The helper uses test_and_set_bit()/test_and_clear_bit() to track > whether the state actually changed, so start_stop_khugepaged() is > only called when needed. When the mode is unchanged, > set_recommended_min_free_kbytes() is called directly to preserve > the watermark recalculation behavior of the original code. > > Signed-off-by: Breno Leitao This is nice, you've improved my idea :) I know you change another instance of this in 3/3, but I wonder if there are other cases like this in the THP code we can fixup too? Anyway, passing tests locally and LGTM so: Reviewed-by: Lorenzo Stoakes (Oracle) > --- > mm/huge_memory.c | 84 +++++++++++++++++++++++++++++++++++--------------------- > 1 file changed, 52 insertions(+), 32 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 8e2746ea74adf..19619213f54d1 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -316,6 +316,20 @@ static ssize_t enabled_show(struct kobject *kobj, > return sysfs_emit(buf, "%s\n", output); > } > > +enum enabled_mode { > + ENABLED_ALWAYS, > + ENABLED_MADVISE, > + ENABLED_INHERIT, > + ENABLED_NEVER, > +}; > + > +static const char * const enabled_mode_strings[] = { > + [ENABLED_ALWAYS] = "always", > + [ENABLED_MADVISE] = "madvise", > + [ENABLED_INHERIT] = "inherit", > + [ENABLED_NEVER] = "never", > +}; > + > static ssize_t enabled_store(struct kobject *kobj, > struct kobj_attribute *attr, > const char *buf, size_t count) > @@ -515,48 +529,54 @@ static ssize_t anon_enabled_show(struct kobject *kobj, > return sysfs_emit(buf, "%s\n", output); > } > > +static bool change_anon_orders(int order, enum enabled_mode mode) > +{ > + static unsigned long *orders[] = { > + &huge_anon_orders_always, > + &huge_anon_orders_madvise, > + &huge_anon_orders_inherit, > + }; > + bool changed = false; > + int i; > + > + spin_lock(&huge_anon_orders_lock); > + for (i = 0; i < ARRAY_SIZE(orders); i++) { > + if (i == mode) > + changed |= !test_and_set_bit(order, orders[i]); > + else > + changed |= test_and_clear_bit(order, orders[i]); > + } > + spin_unlock(&huge_anon_orders_lock); > + > + return changed; > +} > + > static ssize_t anon_enabled_store(struct kobject *kobj, > struct kobj_attribute *attr, > const char *buf, size_t count) > { > int order = to_thpsize(kobj)->order; > - ssize_t ret = count; > + int mode; > > - if (sysfs_streq(buf, "always")) { > - spin_lock(&huge_anon_orders_lock); > - clear_bit(order, &huge_anon_orders_inherit); > - clear_bit(order, &huge_anon_orders_madvise); > - set_bit(order, &huge_anon_orders_always); > - spin_unlock(&huge_anon_orders_lock); > - } else if (sysfs_streq(buf, "inherit")) { > - spin_lock(&huge_anon_orders_lock); > - clear_bit(order, &huge_anon_orders_always); > - clear_bit(order, &huge_anon_orders_madvise); > - set_bit(order, &huge_anon_orders_inherit); > - spin_unlock(&huge_anon_orders_lock); > - } else if (sysfs_streq(buf, "madvise")) { > - spin_lock(&huge_anon_orders_lock); > - clear_bit(order, &huge_anon_orders_always); > - clear_bit(order, &huge_anon_orders_inherit); > - set_bit(order, &huge_anon_orders_madvise); > - spin_unlock(&huge_anon_orders_lock); > - } else if (sysfs_streq(buf, "never")) { > - spin_lock(&huge_anon_orders_lock); > - clear_bit(order, &huge_anon_orders_always); > - clear_bit(order, &huge_anon_orders_inherit); > - clear_bit(order, &huge_anon_orders_madvise); > - spin_unlock(&huge_anon_orders_lock); > - } else > - ret = -EINVAL; > + mode = sysfs_match_string(enabled_mode_strings, buf); > + if (mode < 0) > + return -EINVAL; > > - if (ret > 0) { > - int err; > + if (change_anon_orders(order, mode)) { > + int err = start_stop_khugepaged(); > > - 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 anon_enabled_attr = > > -- > 2.47.3 >