From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 325AEC433EF for ; Fri, 8 Apr 2022 03:50:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234005AbiDHDw0 (ORCPT ); Thu, 7 Apr 2022 23:52:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233981AbiDHDwQ (ORCPT ); Thu, 7 Apr 2022 23:52:16 -0400 Received: from mail-io1-xd31.google.com (mail-io1-xd31.google.com [IPv6:2607:f8b0:4864:20::d31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C23F14B1CF for ; Thu, 7 Apr 2022 20:50:13 -0700 (PDT) Received: by mail-io1-xd31.google.com with SMTP id q11so9245846iod.6 for ; Thu, 07 Apr 2022 20:50:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2QmAYw2YLFK+N9yPKn4RBghklNnQzBJleL0zBPtPDBI=; b=sOPdU5+aYTOb3Ha6VI8yahXVwXAUfRMGetQTs3UZXodIXilTGhISQ2xWnnoNYFbOCE 4w+P0CMEgeaKhwhopVLt3fTsdUJlIZNCRx7v92BnBuDFo5Mw1CwLwOQxMmEhwzt907Km LdWcsGOQJKeuBQVG93y+qP0RiTyTIyA7knvtBivZPWiU1Gxx7CCgXsSvltU5XbPnjtGQ P6WeuYF0IvSYvCLNs4Q5a52B0sleld017mpp59YWGetE+8TzuKF0HHhoWxu+sbpSTu4u L+CvAT5Tu9iaTyZIuG7s5g4HvzoX4UP4FFvzjnL7pwc9+KYaBDn6MuWY1m52qTpiJoiJ P4rQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2QmAYw2YLFK+N9yPKn4RBghklNnQzBJleL0zBPtPDBI=; b=fpgXgmBH6qiA50kVs+4PPqXkY8y+Qxcp+DMt2fZj/yLHqNpvBDtoObtdN1FbXD0vd6 BBCzhaXyq7OIp1SC4IZvfT4/h7jTaEFhR7pDmaajfgRzn7YiRFXiT8ijipJJpgqVn7qt 6RzjdcFlwkWK8vELmtuZwrViRSr0Ohc4Oi+7KFBio1JEDwYou8Rg5c5g0aH8ikkS5zbB ddvvAN3G7yR23viRN9lnB7imeulbaUD3Dx7ccXXkVb3S67RW4oaY9alZDFxtG8LrB/dB OxidkosCxUqIaKA66tgH7DEtFvQUyIyvEuALGGZU7XoPW5K/UD+eo1nhNiKM2dc6WR3L yvFg== X-Gm-Message-State: AOAM530YyhrEXn9nFgUIvw0G0zMOe+6iMyQxzmWkxS2zklEw2oPjozCe JWgHl7iOe5ZdOdDt5yQLgevVbSFw/NvqPaqI0rg4+g== X-Google-Smtp-Source: ABdhPJzeT70Fqcqyx7XHXPZZxZDNBK20yshrycJGbTgJzysj9k7U5NM5HhN6z5qbokPS0PHvCzK70AY7/1z/cbI4/V0= X-Received: by 2002:a05:6602:2c52:b0:646:2488:a9a0 with SMTP id x18-20020a0566022c5200b006462488a9a0mr7651188iov.130.1649389812360; Thu, 07 Apr 2022 20:50:12 -0700 (PDT) MIME-Version: 1.0 References: <20220407224244.1374102-1-yosryahmed@google.com> <20220407224244.1374102-2-yosryahmed@google.com> In-Reply-To: <20220407224244.1374102-2-yosryahmed@google.com> From: Wei Xu Date: Thu, 7 Apr 2022 20:50:01 -0700 Message-ID: Subject: Re: [PATCH v2 1/4] memcg: introduce per-memcg reclaim interface To: Yosry Ahmed Cc: Johannes Weiner , Michal Hocko , Shakeel Butt , Andrew Morton , Roman Gushchin , David Rientjes , Tejun Heo , Zefan Li , Jonathan Corbet , Shuah Khan , Yu Zhao , Dave Hansen , Greg Thelen , Chen Wandun , Vaibhav Jain , Huang@google.com, Ying , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Tim Chen , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Michal Hocko Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 7, 2022 at 3:43 PM Yosry Ahmed wrote: > > From: Shakeel Butt > > Introduce a memcg interface to trigger memory reclaim on a memory cgroup. > > Use case: Proactive Reclaim > --------------------------- > > A userspace proactive reclaimer can continuously probe the memcg to > reclaim a small amount of memory. This gives more accurate and > up-to-date workingset estimation as the LRUs are continuously > sorted and can potentially provide more deterministic memory > overcommit behavior. The memory overcommit controller can provide > more proactive response to the changing behavior of the running > applications instead of being reactive. > > A userspace reclaimer's purpose in this case is not a complete replacement > for kswapd or direct reclaim, it is to proactively identify memory savings > opportunities and reclaim some amount of cold pages set by the policy > to free up the memory for more demanding jobs or scheduling new jobs. > > A user space proactive reclaimer is used in Google data centers. > Additionally, Meta's TMO paper recently referenced a very similar > interface used for user space proactive reclaim: > https://dl.acm.org/doi/pdf/10.1145/3503222.3507731 > > Benefits of a user space reclaimer: > ----------------------------------- > > 1) More flexible on who should be charged for the cpu of the memory > reclaim. For proactive reclaim, it makes more sense to be centralized. > > 2) More flexible on dedicating the resources (like cpu). The memory > overcommit controller can balance the cost between the cpu usage and > the memory reclaimed. > > 3) Provides a way to the applications to keep their LRUs sorted, so, > under memory pressure better reclaim candidates are selected. This also > gives more accurate and uptodate notion of working set for an > application. > > Why memory.high is not enough? > ------------------------------ > > - memory.high can be used to trigger reclaim in a memcg and can > potentially be used for proactive reclaim. > However there is a big downside in using memory.high. It can potentially > introduce high reclaim stalls in the target application as the > allocations from the processes or the threads of the application can hit > the temporary memory.high limit. > > - Userspace proactive reclaimers usually use feedback loops to decide > how much memory to proactively reclaim from a workload. The metrics > used for this are usually either refaults or PSI, and these metrics > will become messy if the application gets throttled by hitting the > high limit. > > - memory.high is a stateful interface, if the userspace proactive > reclaimer crashes for any reason while triggering reclaim it can leave > the application in a bad state. > > - If a workload is rapidly expanding, setting memory.high to proactively > reclaim memory can result in actually reclaiming more memory than > intended. > > The benefits of such interface and shortcomings of existing interface > were further discussed in this RFC thread: > https://lore.kernel.org/linux-mm/5df21376-7dd1-bf81-8414-32a73cea45dd@google.com/ > > Interface: > ---------- > > Introducing a very simple memcg interface 'echo 10M > memory.reclaim' to > trigger reclaim in the target memory cgroup. > > The interface is introduced as a nested-keyed file to allow for future > optional arguments to be easily added to configure the behavior of > reclaim. > > Possible Extensions: > -------------------- > > - This interface can be extended with an additional parameter or flags > to allow specifying one or more types of memory to reclaim from (e.g. > file, anon, ..). > > - The interface can also be extended with a node mask to reclaim from > specific nodes. This has use cases for reclaim-based demotion in memory > tiering systens. > > - A similar per-node interface can also be added to support proactive > reclaim and reclaim-based demotion in systems without memcg. > > - Add a timeout parameter to make it easier for user space to call the > interface without worrying about being blocked for an undefined amount > of time. > > For now, let's keep things simple by adding the basic functionality. > > [yosryahmed@google.com: refreshed to current master, updated commit > message based on recent discussions and use cases] > Signed-off-by: Shakeel Butt > Signed-off-by: Yosry Ahmed > Acked-by: Johannes Weiner > Acked-by: Michal Hocko > --- > Documentation/admin-guide/cgroup-v2.rst | 21 ++++++++++++++ > mm/memcontrol.c | 37 +++++++++++++++++++++++++ > 2 files changed, 58 insertions(+) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > index 69d7a6983f78..19bcd73cad03 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -1208,6 +1208,27 @@ PAGE_SIZE multiple when read back. > high limit is used and monitored properly, this limit's > utility is limited to providing the final safety net. > > + memory.reclaim > + A write-only nested-keyed file which exists for all cgroups. > + > + This is a simple interface to trigger memory reclaim in the > + target cgroup. > + > + This file accepts a single key, the number of bytes to reclaim. > + No nested keys are currently supported. > + > + Example:: > + > + echo "1G" > memory.reclaim > + > + The interface can be later extended with nested keys to > + configure the reclaim behavior. For example, specify the > + type of memory to reclaim from (anon, file, ..). > + > + Please note that the kernel can over or under reclaim from > + the target cgroup. If less bytes are reclaimed than the > + specified amount, -EAGAIN is returned. > + > memory.oom.group > A read-write single value file which exists on non-root > cgroups. The default value is "0". > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 725f76723220..2b214b66d333 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6355,6 +6355,38 @@ static ssize_t memory_oom_group_write(struct kernfs_open_file *of, > return nbytes; > } > > +static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf, > + size_t nbytes, loff_t off) > +{ > + struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of)); > + unsigned int nr_retries = MAX_RECLAIM_RETRIES; > + unsigned long nr_to_reclaim, nr_reclaimed = 0; > + int err; > + > + buf = strstrip(buf); > + err = page_counter_memparse(buf, "", &nr_to_reclaim); > + if (err) > + return err; > + > + while (nr_reclaimed < nr_to_reclaim) { > + unsigned long reclaimed; > + > + if (signal_pending(current)) > + break; > + > + reclaimed = try_to_free_mem_cgroup_pages(memcg, > + nr_to_reclaim - nr_reclaimed, > + GFP_KERNEL, true); > + > + if (!reclaimed && !nr_retries--) > + break; > + > + nr_reclaimed += reclaimed; > + } > + > + return nr_reclaimed < nr_to_reclaim ? -EAGAIN : nbytes; > +} > + > static struct cftype memory_files[] = { > { > .name = "current", > @@ -6413,6 +6445,11 @@ static struct cftype memory_files[] = { > .seq_show = memory_oom_group_show, > .write = memory_oom_group_write, > }, > + { > + .name = "reclaim", > + .flags = CFTYPE_NS_DELEGATABLE, > + .write = memory_reclaim, > + }, > { } /* terminate */ > }; > > -- > 2.35.1.1178.g4f1659d476-goog > Acked-by: Wei Xu From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Xu Subject: Re: [PATCH v2 1/4] memcg: introduce per-memcg reclaim interface Date: Thu, 7 Apr 2022 20:50:01 -0700 Message-ID: References: <20220407224244.1374102-1-yosryahmed@google.com> <20220407224244.1374102-2-yosryahmed@google.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=2QmAYw2YLFK+N9yPKn4RBghklNnQzBJleL0zBPtPDBI=; b=sOPdU5+aYTOb3Ha6VI8yahXVwXAUfRMGetQTs3UZXodIXilTGhISQ2xWnnoNYFbOCE 4w+P0CMEgeaKhwhopVLt3fTsdUJlIZNCRx7v92BnBuDFo5Mw1CwLwOQxMmEhwzt907Km LdWcsGOQJKeuBQVG93y+qP0RiTyTIyA7knvtBivZPWiU1Gxx7CCgXsSvltU5XbPnjtGQ P6WeuYF0IvSYvCLNs4Q5a52B0sleld017mpp59YWGetE+8TzuKF0HHhoWxu+sbpSTu4u L+CvAT5Tu9iaTyZIuG7s5g4HvzoX4UP4FFvzjnL7pwc9+KYaBDn6MuWY1m52qTpiJoiJ P4rQ== In-Reply-To: <20220407224244.1374102-2-yosryahmed@google.com> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Yosry Ahmed Cc: Johannes Weiner , Michal Hocko , Shakeel Butt , Andrew Morton , Roman Gushchin , David Rientjes , Tejun Heo , Zefan Li , Jonathan Corbet , Shuah Khan , Yu Zhao , Dave Hansen , Greg Thelen , Chen Wandun , Vaibhav Jain , Huang@google.com, Ying , =?UTF-8?Q?Michal_Koutn=C3=BD?= , Tim Chen , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org On Thu, Apr 7, 2022 at 3:43 PM Yosry Ahmed wrote: > > From: Shakeel Butt > > Introduce a memcg interface to trigger memory reclaim on a memory cgroup. > > Use case: Proactive Reclaim > --------------------------- > > A userspace proactive reclaimer can continuously probe the memcg to > reclaim a small amount of memory. This gives more accurate and > up-to-date workingset estimation as the LRUs are continuously > sorted and can potentially provide more deterministic memory > overcommit behavior. The memory overcommit controller can provide > more proactive response to the changing behavior of the running > applications instead of being reactive. > > A userspace reclaimer's purpose in this case is not a complete replacement > for kswapd or direct reclaim, it is to proactively identify memory savings > opportunities and reclaim some amount of cold pages set by the policy > to free up the memory for more demanding jobs or scheduling new jobs. > > A user space proactive reclaimer is used in Google data centers. > Additionally, Meta's TMO paper recently referenced a very similar > interface used for user space proactive reclaim: > https://dl.acm.org/doi/pdf/10.1145/3503222.3507731 > > Benefits of a user space reclaimer: > ----------------------------------- > > 1) More flexible on who should be charged for the cpu of the memory > reclaim. For proactive reclaim, it makes more sense to be centralized. > > 2) More flexible on dedicating the resources (like cpu). The memory > overcommit controller can balance the cost between the cpu usage and > the memory reclaimed. > > 3) Provides a way to the applications to keep their LRUs sorted, so, > under memory pressure better reclaim candidates are selected. This also > gives more accurate and uptodate notion of working set for an > application. > > Why memory.high is not enough? > ------------------------------ > > - memory.high can be used to trigger reclaim in a memcg and can > potentially be used for proactive reclaim. > However there is a big downside in using memory.high. It can potentially > introduce high reclaim stalls in the target application as the > allocations from the processes or the threads of the application can hit > the temporary memory.high limit. > > - Userspace proactive reclaimers usually use feedback loops to decide > how much memory to proactively reclaim from a workload. The metrics > used for this are usually either refaults or PSI, and these metrics > will become messy if the application gets throttled by hitting the > high limit. > > - memory.high is a stateful interface, if the userspace proactive > reclaimer crashes for any reason while triggering reclaim it can leave > the application in a bad state. > > - If a workload is rapidly expanding, setting memory.high to proactively > reclaim memory can result in actually reclaiming more memory than > intended. > > The benefits of such interface and shortcomings of existing interface > were further discussed in this RFC thread: > https://lore.kernel.org/linux-mm/5df21376-7dd1-bf81-8414-32a73cea45dd@google.com/ > > Interface: > ---------- > > Introducing a very simple memcg interface 'echo 10M > memory.reclaim' to > trigger reclaim in the target memory cgroup. > > The interface is introduced as a nested-keyed file to allow for future > optional arguments to be easily added to configure the behavior of > reclaim. > > Possible Extensions: > -------------------- > > - This interface can be extended with an additional parameter or flags > to allow specifying one or more types of memory to reclaim from (e.g. > file, anon, ..). > > - The interface can also be extended with a node mask to reclaim from > specific nodes. This has use cases for reclaim-based demotion in memory > tiering systens. > > - A similar per-node interface can also be added to support proactive > reclaim and reclaim-based demotion in systems without memcg. > > - Add a timeout parameter to make it easier for user space to call the > interface without worrying about being blocked for an undefined amount > of time. > > For now, let's keep things simple by adding the basic functionality. > > [yosryahmed@google.com: refreshed to current master, updated commit > message based on recent discussions and use cases] > Signed-off-by: Shakeel Butt > Signed-off-by: Yosry Ahmed > Acked-by: Johannes Weiner > Acked-by: Michal Hocko > --- > Documentation/admin-guide/cgroup-v2.rst | 21 ++++++++++++++ > mm/memcontrol.c | 37 +++++++++++++++++++++++++ > 2 files changed, 58 insertions(+) > > diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst > index 69d7a6983f78..19bcd73cad03 100644 > --- a/Documentation/admin-guide/cgroup-v2.rst > +++ b/Documentation/admin-guide/cgroup-v2.rst > @@ -1208,6 +1208,27 @@ PAGE_SIZE multiple when read back. > high limit is used and monitored properly, this limit's > utility is limited to providing the final safety net. > > + memory.reclaim > + A write-only nested-keyed file which exists for all cgroups. > + > + This is a simple interface to trigger memory reclaim in the > + target cgroup. > + > + This file accepts a single key, the number of bytes to reclaim. > + No nested keys are currently supported. > + > + Example:: > + > + echo "1G" > memory.reclaim > + > + The interface can be later extended with nested keys to > + configure the reclaim behavior. For example, specify the > + type of memory to reclaim from (anon, file, ..). > + > + Please note that the kernel can over or under reclaim from > + the target cgroup. If less bytes are reclaimed than the > + specified amount, -EAGAIN is returned. > + > memory.oom.group > A read-write single value file which exists on non-root > cgroups. The default value is "0". > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 725f76723220..2b214b66d333 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6355,6 +6355,38 @@ static ssize_t memory_oom_group_write(struct kernfs_open_file *of, > return nbytes; > } > > +static ssize_t memory_reclaim(struct kernfs_open_file *of, char *buf, > + size_t nbytes, loff_t off) > +{ > + struct mem_cgroup *memcg = mem_cgroup_from_css(of_css(of)); > + unsigned int nr_retries = MAX_RECLAIM_RETRIES; > + unsigned long nr_to_reclaim, nr_reclaimed = 0; > + int err; > + > + buf = strstrip(buf); > + err = page_counter_memparse(buf, "", &nr_to_reclaim); > + if (err) > + return err; > + > + while (nr_reclaimed < nr_to_reclaim) { > + unsigned long reclaimed; > + > + if (signal_pending(current)) > + break; > + > + reclaimed = try_to_free_mem_cgroup_pages(memcg, > + nr_to_reclaim - nr_reclaimed, > + GFP_KERNEL, true); > + > + if (!reclaimed && !nr_retries--) > + break; > + > + nr_reclaimed += reclaimed; > + } > + > + return nr_reclaimed < nr_to_reclaim ? -EAGAIN : nbytes; > +} > + > static struct cftype memory_files[] = { > { > .name = "current", > @@ -6413,6 +6445,11 @@ static struct cftype memory_files[] = { > .seq_show = memory_oom_group_show, > .write = memory_oom_group_write, > }, > + { > + .name = "reclaim", > + .flags = CFTYPE_NS_DELEGATABLE, > + .write = memory_reclaim, > + }, > { } /* terminate */ > }; > > -- > 2.35.1.1178.g4f1659d476-goog > Acked-by: Wei Xu