From patchwork Thu Apr 1 21:42:57 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12179645 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75F8AC43462 for ; Thu, 1 Apr 2021 21:43:16 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1753460FED for ; Thu, 1 Apr 2021 21:43:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1753460FED Authentication-Results: mail.kernel.org; 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Thu, 1 Apr 2021 14:43:07 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 3F10B5C2F8E7; Thu, 1 Apr 2021 14:43:04 -0700 (PDT) From: Roman Gushchin To: Dennis Zhou CC: Tejun Heo , Christoph Lameter , Andrew Morton , , , Roman Gushchin Subject: [PATCH v1 1/5] percpu: split __pcpu_balance_workfn() Date: Thu, 1 Apr 2021 14:42:57 -0700 Message-ID: <20210401214301.1689099-2-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210401214301.1689099-1-guro@fb.com> References: <20210401214301.1689099-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: KrV35OGXcwl2OJ6oZLswykCbM35HJLEk X-Proofpoint-ORIG-GUID: KrV35OGXcwl2OJ6oZLswykCbM35HJLEk X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-04-01_13:2021-04-01,2021-04-01 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 adultscore=0 clxscore=1015 spamscore=0 impostorscore=0 phishscore=0 bulkscore=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2103310000 definitions=main-2104010138 X-FB-Internal: deliver X-Rspamd-Queue-Id: 1B8B4E000100 X-Stat-Signature: aqiq9hzc8iw1hj3e5wkf5jsicu4txk6g X-Rspamd-Server: rspam02 Received-SPF: none (fb.com>: No applicable sender policy available) receiver=imf30; identity=mailfrom; envelope-from=""; helo=mx0a-00082601.pphosted.com; client-ip=67.231.145.42 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617313388-976031 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: __pcpu_balance_workfn() became fairly big and hard to follow, but in fact it consists of two fully independent parts, responsible for the destruction of excessive free chunks and population of necessarily amount of free pages. In order to simplify the code and prepare for adding of a new functionality, split it in two functions: 1) pcpu_balance_free, 2) pcpu_balance_populated. Move the taking/releasing of the pcpu_alloc_mutex to an upper level to keep the current synchronization in place. Signed-off-by: Roman Gushchin Reviewed-by: Dennis Zhou --- mm/percpu.c | 46 +++++++++++++++++++++++++++++----------------- 1 file changed, 29 insertions(+), 17 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index 6596a0a4286e..5b505a459028 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1930,31 +1930,22 @@ void __percpu *__alloc_reserved_percpu(size_t size, size_t align) } /** - * __pcpu_balance_workfn - manage the amount of free chunks and populated pages + * pcpu_balance_free - manage the amount of free chunks * @type: chunk type * - * Reclaim all fully free chunks except for the first one. This is also - * responsible for maintaining the pool of empty populated pages. However, - * it is possible that this is called when physical memory is scarce causing - * OOM killer to be triggered. We should avoid doing so until an actual - * allocation causes the failure as it is possible that requests can be - * serviced from already backed regions. + * Reclaim all fully free chunks except for the first one. */ -static void __pcpu_balance_workfn(enum pcpu_chunk_type type) +static void pcpu_balance_free(enum pcpu_chunk_type type) { - /* gfp flags passed to underlying allocators */ - const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN; LIST_HEAD(to_free); struct list_head *pcpu_slot = pcpu_chunk_list(type); struct list_head *free_head = &pcpu_slot[pcpu_nr_slots - 1]; struct pcpu_chunk *chunk, *next; - int slot, nr_to_pop, ret; /* * There's no reason to keep around multiple unused chunks and VM * areas can be scarce. Destroy all free chunks except for one. */ - mutex_lock(&pcpu_alloc_mutex); spin_lock_irq(&pcpu_lock); list_for_each_entry_safe(chunk, next, free_head, list) { @@ -1982,6 +1973,25 @@ static void __pcpu_balance_workfn(enum pcpu_chunk_type type) pcpu_destroy_chunk(chunk); cond_resched(); } +} + +/** + * pcpu_balance_populated - manage the amount of populated pages + * @type: chunk type + * + * Maintain a certain amount of populated pages to satisfy atomic allocations. + * It is possible that this is called when physical memory is scarce causing + * OOM killer to be triggered. We should avoid doing so until an actual + * allocation causes the failure as it is possible that requests can be + * serviced from already backed regions. + */ +static void pcpu_balance_populated(enum pcpu_chunk_type type) +{ + /* gfp flags passed to underlying allocators */ + const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN; + struct list_head *pcpu_slot = pcpu_chunk_list(type); + struct pcpu_chunk *chunk; + int slot, nr_to_pop, ret; /* * Ensure there are certain number of free populated pages for @@ -2051,22 +2061,24 @@ static void __pcpu_balance_workfn(enum pcpu_chunk_type type) goto retry_pop; } } - - mutex_unlock(&pcpu_alloc_mutex); } /** * pcpu_balance_workfn - manage the amount of free chunks and populated pages * @work: unused * - * Call __pcpu_balance_workfn() for each chunk type. + * Call pcpu_balance_free() and pcpu_balance_populated() for each chunk type. */ static void pcpu_balance_workfn(struct work_struct *work) { enum pcpu_chunk_type type; - for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++) - __pcpu_balance_workfn(type); + for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++) { + mutex_lock(&pcpu_alloc_mutex); + pcpu_balance_free(type); + pcpu_balance_populated(type); + mutex_unlock(&pcpu_alloc_mutex); + } } /** From patchwork Thu Apr 1 21:42:58 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12179649 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7222C43603 for ; Thu, 1 Apr 2021 21:43:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5A51660FED for ; 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Thu, 01 Apr 2021 14:43:10 -0700 Received: from intmgw003.48.prn1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::c) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 1 Apr 2021 14:43:07 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 44A325C2F8E9; Thu, 1 Apr 2021 14:43:04 -0700 (PDT) From: Roman Gushchin To: Dennis Zhou CC: Tejun Heo , Christoph Lameter , Andrew Morton , , , Roman Gushchin Subject: [PATCH v1 2/5] percpu: make pcpu_nr_empty_pop_pages per chunk type Date: Thu, 1 Apr 2021 14:42:58 -0700 Message-ID: <20210401214301.1689099-3-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210401214301.1689099-1-guro@fb.com> References: <20210401214301.1689099-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: ncKfIHvqL8oTmUAHQ5M_rOwcj5UEzAtr X-Proofpoint-ORIG-GUID: ncKfIHvqL8oTmUAHQ5M_rOwcj5UEzAtr X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-04-01_13:2021-04-01,2021-04-01 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 adultscore=0 clxscore=1015 spamscore=0 impostorscore=0 phishscore=0 bulkscore=0 priorityscore=1501 mlxlogscore=999 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2103310000 definitions=main-2104010138 X-FB-Internal: deliver X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2F598C0007C3 X-Stat-Signature: 31p3e8fb1gammumnuu7ncoygx6sknw39 Received-SPF: none (fb.com>: No applicable sender policy available) receiver=imf03; identity=mailfrom; envelope-from=""; helo=mx0a-00082601.pphosted.com; client-ip=67.231.145.42 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617313389-827146 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: nr_empty_pop_pages is used to guarantee that there are some free populated pages to satisfy atomic allocations. Accounted and non-accounted allocations are using separate sets of chunks, so both need to have a surplus of empty pages. This commit makes pcpu_nr_empty_pop_pages and the corresponding logic per chunk type. Signed-off-by: Roman Gushchin --- mm/percpu-internal.h | 2 +- mm/percpu-stats.c | 9 +++++++-- mm/percpu.c | 14 +++++++------- 3 files changed, 15 insertions(+), 10 deletions(-) diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index 18b768ac7dca..095d7eaa0db4 100644 --- a/mm/percpu-internal.h +++ b/mm/percpu-internal.h @@ -87,7 +87,7 @@ extern spinlock_t pcpu_lock; extern struct list_head *pcpu_chunk_lists; extern int pcpu_nr_slots; -extern int pcpu_nr_empty_pop_pages; +extern int pcpu_nr_empty_pop_pages[]; extern struct pcpu_chunk *pcpu_first_chunk; extern struct pcpu_chunk *pcpu_reserved_chunk; diff --git a/mm/percpu-stats.c b/mm/percpu-stats.c index c8400a2adbc2..f6026dbcdf6b 100644 --- a/mm/percpu-stats.c +++ b/mm/percpu-stats.c @@ -145,6 +145,7 @@ static int percpu_stats_show(struct seq_file *m, void *v) int slot, max_nr_alloc; int *buffer; enum pcpu_chunk_type type; + int nr_empty_pop_pages; alloc_buffer: spin_lock_irq(&pcpu_lock); @@ -165,7 +166,11 @@ static int percpu_stats_show(struct seq_file *m, void *v) goto alloc_buffer; } -#define PL(X) \ + nr_empty_pop_pages = 0; + for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++) + nr_empty_pop_pages += pcpu_nr_empty_pop_pages[type]; + +#define PL(X) \ seq_printf(m, " %-20s: %12lld\n", #X, (long long int)pcpu_stats_ai.X) seq_printf(m, @@ -196,7 +201,7 @@ static int percpu_stats_show(struct seq_file *m, void *v) PU(nr_max_chunks); PU(min_alloc_size); PU(max_alloc_size); - P("empty_pop_pages", pcpu_nr_empty_pop_pages); + P("empty_pop_pages", nr_empty_pop_pages); seq_putc(m, '\n'); #undef PU diff --git a/mm/percpu.c b/mm/percpu.c index 5b505a459028..0eeeb4e7a2f9 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -173,10 +173,10 @@ struct list_head *pcpu_chunk_lists __ro_after_init; /* chunk list slots */ static LIST_HEAD(pcpu_map_extend_chunks); /* - * The number of empty populated pages, protected by pcpu_lock. The - * reserved chunk doesn't contribute to the count. + * The number of empty populated pages by chunk type, protected by pcpu_lock. + * The reserved chunk doesn't contribute to the count. */ -int pcpu_nr_empty_pop_pages; +int pcpu_nr_empty_pop_pages[PCPU_NR_CHUNK_TYPES]; /* * The number of populated pages in use by the allocator, protected by @@ -556,7 +556,7 @@ static inline void pcpu_update_empty_pages(struct pcpu_chunk *chunk, int nr) { chunk->nr_empty_pop_pages += nr; if (chunk != pcpu_reserved_chunk) - pcpu_nr_empty_pop_pages += nr; + pcpu_nr_empty_pop_pages[pcpu_chunk_type(chunk)] += nr; } /* @@ -1832,7 +1832,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, mutex_unlock(&pcpu_alloc_mutex); } - if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW) + if (pcpu_nr_empty_pop_pages[type] < PCPU_EMPTY_POP_PAGES_LOW) pcpu_schedule_balance_work(); /* clear the areas and return address relative to base address */ @@ -2010,7 +2010,7 @@ static void pcpu_balance_populated(enum pcpu_chunk_type type) pcpu_atomic_alloc_failed = false; } else { nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH - - pcpu_nr_empty_pop_pages, + pcpu_nr_empty_pop_pages[type], 0, PCPU_EMPTY_POP_PAGES_HIGH); } @@ -2592,7 +2592,7 @@ void __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, /* link the first chunk in */ pcpu_first_chunk = chunk; - pcpu_nr_empty_pop_pages = pcpu_first_chunk->nr_empty_pop_pages; + pcpu_nr_empty_pop_pages[PCPU_CHUNK_ROOT] = pcpu_first_chunk->nr_empty_pop_pages; pcpu_chunk_relocate(pcpu_first_chunk, -1); /* include all regions of the first chunk */ From patchwork Thu Apr 1 21:42:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12179639 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26BF8C433ED for ; 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Thu, 01 Apr 2021 14:43:09 -0700 Received: from intmgw002.48.prn1.facebook.com (2620:10d:c0a8:1b::d) by mail.thefacebook.com (2620:10d:c0a8:82::f) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 1 Apr 2021 14:43:08 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 49ECE5C2F8EB; Thu, 1 Apr 2021 14:43:04 -0700 (PDT) From: Roman Gushchin To: Dennis Zhou CC: Tejun Heo , Christoph Lameter , Andrew Morton , , , Roman Gushchin Subject: [PATCH v1 3/5] percpu: generalize pcpu_balance_populated() Date: Thu, 1 Apr 2021 14:42:59 -0700 Message-ID: <20210401214301.1689099-4-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210401214301.1689099-1-guro@fb.com> References: <20210401214301.1689099-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: sZoQXE7zTG_HHLGB4q_-rx1-imi75jLc X-Proofpoint-ORIG-GUID: sZoQXE7zTG_HHLGB4q_-rx1-imi75jLc X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-04-01_13:2021-04-01,2021-04-01 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 clxscore=1015 phishscore=0 mlxscore=0 adultscore=0 malwarescore=0 suspectscore=0 bulkscore=0 spamscore=0 mlxlogscore=999 lowpriorityscore=0 impostorscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2103310000 definitions=main-2104010138 X-FB-Internal: deliver X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 6016E80192D5 X-Stat-Signature: bqdi8dfbyjekhcubpx8hys378iwnrkju Received-SPF: none (fb.com>: No applicable sender policy available) receiver=imf16; identity=mailfrom; envelope-from=""; helo=mx0a-00082601.pphosted.com; client-ip=67.231.153.30 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617313389-689095 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: To prepare for the depopulation of percpu chunks, split out the populating part of the pcpu_balance_populated() into the new pcpu_grow_populated() (with an intention to add pcpu_shrink_populated() in the next commit). The goal of pcpu_balance_populated() is to determine whether there is a shortage or an excessive amount of empty percpu pages and call into the corresponding function. pcpu_grow_populated() takes a desired number of pages as an argument (nr_to_pop). If it creates a new chunk, nr_to_pop should be updated to reflect that the new chunk could be created already populated. Otherwise an infinite loop might appear. Signed-off-by: Roman Gushchin --- mm/percpu.c | 63 +++++++++++++++++++++++++++++++++-------------------- 1 file changed, 39 insertions(+), 24 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index 0eeeb4e7a2f9..25a181328353 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1976,7 +1976,7 @@ static void pcpu_balance_free(enum pcpu_chunk_type type) } /** - * pcpu_balance_populated - manage the amount of populated pages + * pcpu_grow_populated - populate chunk(s) to satisfy atomic allocations * @type: chunk type * * Maintain a certain amount of populated pages to satisfy atomic allocations. @@ -1985,35 +1985,15 @@ static void pcpu_balance_free(enum pcpu_chunk_type type) * allocation causes the failure as it is possible that requests can be * serviced from already backed regions. */ -static void pcpu_balance_populated(enum pcpu_chunk_type type) +static void pcpu_grow_populated(enum pcpu_chunk_type type, int nr_to_pop) { /* gfp flags passed to underlying allocators */ const gfp_t gfp = GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN; struct list_head *pcpu_slot = pcpu_chunk_list(type); struct pcpu_chunk *chunk; - int slot, nr_to_pop, ret; + int slot, ret; - /* - * Ensure there are certain number of free populated pages for - * atomic allocs. Fill up from the most packed so that atomic - * allocs don't increase fragmentation. If atomic allocation - * failed previously, always populate the maximum amount. This - * should prevent atomic allocs larger than PAGE_SIZE from keeping - * failing indefinitely; however, large atomic allocs are not - * something we support properly and can be highly unreliable and - * inefficient. - */ retry_pop: - if (pcpu_atomic_alloc_failed) { - nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH; - /* best effort anyway, don't worry about synchronization */ - pcpu_atomic_alloc_failed = false; - } else { - nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH - - pcpu_nr_empty_pop_pages[type], - 0, PCPU_EMPTY_POP_PAGES_HIGH); - } - for (slot = pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot++) { unsigned int nr_unpop = 0, rs, re; @@ -2057,12 +2037,47 @@ static void pcpu_balance_populated(enum pcpu_chunk_type type) if (chunk) { spin_lock_irq(&pcpu_lock); pcpu_chunk_relocate(chunk, -1); + nr_to_pop = max_t(int, 0, nr_to_pop - chunk->nr_populated); spin_unlock_irq(&pcpu_lock); - goto retry_pop; + if (nr_to_pop) + goto retry_pop; } } } +/** + * pcpu_balance_populated - manage the amount of populated pages + * @type: chunk type + * + * Populate or depopulate chunks to maintain a certain amount + * of free pages to satisfy atomic allocations, but not waste + * large amounts of memory. + */ +static void pcpu_balance_populated(enum pcpu_chunk_type type) +{ + int nr_to_pop; + + /* + * Ensure there are certain number of free populated pages for + * atomic allocs. Fill up from the most packed so that atomic + * allocs don't increase fragmentation. If atomic allocation + * failed previously, always populate the maximum amount. This + * should prevent atomic allocs larger than PAGE_SIZE from keeping + * failing indefinitely; however, large atomic allocs are not + * something we support properly and can be highly unreliable and + * inefficient. + */ + if (pcpu_atomic_alloc_failed) { + nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH; + /* best effort anyway, don't worry about synchronization */ + pcpu_atomic_alloc_failed = false; + pcpu_grow_populated(type, nr_to_pop); + } else if (pcpu_nr_empty_pop_pages[type] < PCPU_EMPTY_POP_PAGES_HIGH) { + nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH - pcpu_nr_empty_pop_pages[type]; + pcpu_grow_populated(type, nr_to_pop); + } +} + /** * pcpu_balance_workfn - manage the amount of free chunks and populated pages * @work: unused From patchwork Thu Apr 1 21:43:00 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12179643 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D833DC43460 for ; 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Thu, 01 Apr 2021 14:43:09 -0700 Received: from intmgw001.27.prn2.facebook.com (2620:10d:c085:108::4) by mail.thefacebook.com (2620:10d:c085:11d::4) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 1 Apr 2021 14:43:09 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 4EF8B5C2F8ED; Thu, 1 Apr 2021 14:43:04 -0700 (PDT) From: Roman Gushchin To: Dennis Zhou CC: Tejun Heo , Christoph Lameter , Andrew Morton , , , Roman Gushchin Subject: [PATCH v1 4/5] percpu: fix a comment about the chunks ordering Date: Thu, 1 Apr 2021 14:43:00 -0700 Message-ID: <20210401214301.1689099-5-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210401214301.1689099-1-guro@fb.com> References: <20210401214301.1689099-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: k5XQxmz1ArEQGWUZMCTFWlaQqifBdco3 X-Proofpoint-ORIG-GUID: k5XQxmz1ArEQGWUZMCTFWlaQqifBdco3 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-04-01_13:2021-04-01,2021-04-01 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxscore=0 priorityscore=1501 impostorscore=0 suspectscore=0 mlxlogscore=849 malwarescore=0 spamscore=0 adultscore=0 phishscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2103310000 definitions=main-2104010138 X-FB-Internal: deliver X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 010B120001D6 X-Stat-Signature: 94tqjuuxh9qjottng7xn8f3fac597wqa Received-SPF: none (fb.com>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from=""; helo=mx0a-00082601.pphosted.com; client-ip=67.231.145.42 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617313389-620216 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Since the commit 3e54097beb22 ("percpu: manage chunks based on contig_bits instead of free_bytes") chunks are sorted based on the size of the biggest continuous free area instead of the total number of free bytes. Update the corresponding comment to reflect this. Signed-off-by: Roman Gushchin --- mm/percpu.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/percpu.c b/mm/percpu.c index 25a181328353..e20119668c42 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -99,7 +99,10 @@ #include "percpu-internal.h" -/* the slots are sorted by free bytes left, 1-31 bytes share the same slot */ +/* + * The slots are sorted by the size of the biggest continuous free area. + * 1-31 bytes share the same slot. + */ #define PCPU_SLOT_BASE_SHIFT 5 /* chunks in slots below this are subject to being sidelined on failed alloc */ #define PCPU_SLOT_FAIL_THRESHOLD 3 From patchwork Thu Apr 1 21:43:01 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Roman Gushchin X-Patchwork-Id: 12179647 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8CF92C433ED for ; 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Thu, 01 Apr 2021 14:43:10 -0700 Received: from intmgw001.27.prn2.facebook.com (2620:10d:c085:208::f) by mail.thefacebook.com (2620:10d:c085:11d::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.2; Thu, 1 Apr 2021 14:43:09 -0700 Received: by devvm3388.prn0.facebook.com (Postfix, from userid 111017) id 545555C2F8EF; Thu, 1 Apr 2021 14:43:04 -0700 (PDT) From: Roman Gushchin To: Dennis Zhou CC: Tejun Heo , Christoph Lameter , Andrew Morton , , , Roman Gushchin Subject: [PATCH v1 5/5] percpu: implement partial chunk depopulation Date: Thu, 1 Apr 2021 14:43:01 -0700 Message-ID: <20210401214301.1689099-6-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210401214301.1689099-1-guro@fb.com> References: <20210401214301.1689099-1-guro@fb.com> MIME-Version: 1.0 X-FB-Internal: Safe X-Proofpoint-GUID: 2b9iWeMyCjbvq5Bq0fcsapWlLw4C8jAB X-Proofpoint-ORIG-GUID: 2b9iWeMyCjbvq5Bq0fcsapWlLw4C8jAB X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369,18.0.761 definitions=2021-04-01_13:2021-04-01,2021-04-01 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0 malwarescore=0 mlxscore=0 adultscore=0 clxscore=1015 spamscore=0 impostorscore=0 phishscore=0 bulkscore=0 priorityscore=1501 mlxlogscore=681 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2103310000 definitions=main-2104010138 X-FB-Internal: deliver X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: F0C5440002CE X-Stat-Signature: 6kyst6a79e1n5p1ry5izhnxi4jb9yg4q Received-SPF: none (fb.com>: No applicable sender policy available) receiver=imf10; identity=mailfrom; envelope-from=""; helo=mx0a-00082601.pphosted.com; client-ip=67.231.145.42 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617313389-658442 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: This patch implements partial depopulation of percpu chunks. As now, a chunk can be depopulated only as a part of the final destruction, if there are no more outstanding allocations. However to minimize a memory waste it might be useful to depopulate a partially filed chunk, if a small number of outstanding allocations prevents the chunk from being fully reclaimed. This patch implements the following depopulation process: it scans over the chunk pages, looks for a range of empty and populated pages and performs the depopulation. To avoid races with new allocations, the chunk is previously isolated. After the depopulation the chunk is returned to the original slot (but is appended to the tail of the list to minimize the chances of population). Because the pcpu_lock is dropped while calling pcpu_depopulate_chunk(), the chunk can be concurrently moved to a different slot. To prevent this, bool chunk->isolated flag is introduced. If set, the chunk can't be moved to a different slot. The depopulation is scheduled on the free path. Is the chunk: 1) has more than 1/8 of total pages free and populated 2) the system has enough free percpu pages aside of this chunk 3) isn't the reserved chunk 4) isn't the first chunk 5) isn't entirely free it's a good target for depopulation. If so, the chunk is moved to a special pcpu_depopulate_list, chunk->isolate flag is set and the async balancing is scheduled. The async balancing moves pcpu_depopulate_list to a local list (because pcpu_depopulate_list can be changed when pcpu_lock is releases), and then tries to depopulate each chunk. Successfully or not, at the end all chunks are returned to appropriate slots and their isolated flags are cleared. Many thanks to Dennis Zhou for his great ideas and a very constructive discussion which led to many improvements in this patchset! Signed-off-by: Roman Gushchin --- mm/percpu-internal.h | 1 + mm/percpu.c | 101 ++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 100 insertions(+), 2 deletions(-) diff --git a/mm/percpu-internal.h b/mm/percpu-internal.h index 095d7eaa0db4..ff318752915d 100644 --- a/mm/percpu-internal.h +++ b/mm/percpu-internal.h @@ -67,6 +67,7 @@ struct pcpu_chunk { void *data; /* chunk data */ bool immutable; /* no [de]population allowed */ + bool isolated; /* isolated from chunk slot lists */ int start_offset; /* the overlap with the previous region to have a page aligned base_addr */ diff --git a/mm/percpu.c b/mm/percpu.c index e20119668c42..dae0b870e10a 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -181,6 +181,12 @@ static LIST_HEAD(pcpu_map_extend_chunks); */ int pcpu_nr_empty_pop_pages[PCPU_NR_CHUNK_TYPES]; +/* + * List of chunks with a lot of free pages. Used to depopulate them + * asynchronously. + */ +static LIST_HEAD(pcpu_depopulate_list); + /* * The number of populated pages in use by the allocator, protected by * pcpu_lock. This number is kept per a unit per chunk (i.e. when a page gets @@ -542,7 +548,7 @@ static void pcpu_chunk_relocate(struct pcpu_chunk *chunk, int oslot) { int nslot = pcpu_chunk_slot(chunk); - if (oslot != nslot) + if (!chunk->isolated && oslot != nslot) __pcpu_chunk_move(chunk, nslot, oslot < nslot); } @@ -2048,6 +2054,82 @@ static void pcpu_grow_populated(enum pcpu_chunk_type type, int nr_to_pop) } } +/** + * pcpu_shrink_populated - scan chunks and release unused pages to the system + * @type: chunk type + * + * Scan over all chunks, find those marked with the depopulate flag and + * try to release unused pages to the system. On every attempt clear the + * chunk's depopulate flag to avoid wasting CPU by scanning the same + * chunk again and again. + */ +static void pcpu_shrink_populated(enum pcpu_chunk_type type) +{ + struct pcpu_block_md *block; + struct pcpu_chunk *chunk, *tmp; + LIST_HEAD(to_depopulate); + int i, start; + + spin_lock_irq(&pcpu_lock); + + list_splice_init(&pcpu_depopulate_list, &to_depopulate); + + list_for_each_entry_safe(chunk, tmp, &to_depopulate, list) { + WARN_ON(chunk->immutable); + + for (i = 0, start = -1; i < chunk->nr_pages; i++) { + /* + * If the chunk has no empty pages or + * we're short on empty pages in general, + * just put the chunk back into the original slot. + */ + if (!chunk->nr_empty_pop_pages || + pcpu_nr_empty_pop_pages[type] < + PCPU_EMPTY_POP_PAGES_HIGH) + break; + + /* + * If the page is empty and populated, start or + * extend the [start, i) range. + */ + block = chunk->md_blocks + i; + if (block->contig_hint == PCPU_BITMAP_BLOCK_BITS && + test_bit(i, chunk->populated)) { + if (start == -1) + start = i; + continue; + } + + /* + * Otherwise check if there is an active range, + * and if yes, depopulate it. + */ + if (start == -1) + continue; + + spin_unlock_irq(&pcpu_lock); + pcpu_depopulate_chunk(chunk, start, i); + cond_resched(); + spin_lock_irq(&pcpu_lock); + + pcpu_chunk_depopulated(chunk, start, i); + + /* + * Reset the range and continue. + */ + start = -1; + } + + /* + * Return the chunk to the corresponding slot. + */ + chunk->isolated = false; + pcpu_chunk_relocate(chunk, -1); + } + + spin_unlock_irq(&pcpu_lock); +} + /** * pcpu_balance_populated - manage the amount of populated pages * @type: chunk type @@ -2078,6 +2160,8 @@ static void pcpu_balance_populated(enum pcpu_chunk_type type) } else if (pcpu_nr_empty_pop_pages[type] < PCPU_EMPTY_POP_PAGES_HIGH) { nr_to_pop = PCPU_EMPTY_POP_PAGES_HIGH - pcpu_nr_empty_pop_pages[type]; pcpu_grow_populated(type, nr_to_pop); + } else if (!list_empty(&pcpu_depopulate_list)) { + pcpu_shrink_populated(type); } } @@ -2135,7 +2219,12 @@ void free_percpu(void __percpu *ptr) pcpu_memcg_free_hook(chunk, off, size); - /* if there are more than one fully free chunks, wake up grim reaper */ + /* + * If there are more than one fully free chunks, wake up grim reaper. + * Otherwise if at least 1/8 of its pages are empty and there is no + * system-wide shortage of empty pages aside from this chunk, isolate + * the chunk and schedule an async depopulation. + */ if (chunk->free_bytes == pcpu_unit_size) { struct pcpu_chunk *pos; @@ -2144,6 +2233,14 @@ void free_percpu(void __percpu *ptr) need_balance = true; break; } + } else if (chunk != pcpu_first_chunk && chunk != pcpu_reserved_chunk && + !chunk->isolated && + chunk->nr_empty_pop_pages >= chunk->nr_pages / 8 && + pcpu_nr_empty_pop_pages[pcpu_chunk_type(chunk)] > + PCPU_EMPTY_POP_PAGES_HIGH + chunk->nr_empty_pop_pages) { + list_move(&chunk->list, &pcpu_depopulate_list); + chunk->isolated = true; + need_balance = true; } trace_percpu_free_percpu(chunk->base_addr, off, ptr);